Subirdia: Birds adapt to the Anthropocene

 

christmas-holly-4This article is our Christmas present to our readers.  We celebrate the holidays with good news about the birds living in cities all over the world.

Subirdia was written by John Marzluff, an academic ornithologist at University of Washington. (1)  He reports many years of his research and that of his graduate students about the birds that live in urban and suburban Seattle as well as surrounding forest reserves.  He also reports on countless studies of bird populations in similar settings all over the world.  All of those studies reach remarkably similar conclusions.

It took me a long time to read this book because its introduction was off-putting.  Virtually every plant and animal was preceded by the qualifier of “native” or “non-native.”  The implication of the introduction was that the most important feature of every plant and animal is whether or not it is native.  As our readers know, we consider the nativity of plant and animal species largely irrelevant.  All plants and animals are at home in our ideal nature.

Owl nesting in eucalyptus, courtesy urbanwildness.com
Owl nesting in eucalyptus, courtesy urbanwildness.com

When I finally got around to reading Subirdia I was pleasantly surprised.  Although the author has a preference for native plants and animals, in fact, his research and that of others does not justify his obsession.  Where birds are actually found in the greatest numbers is where the habitat is most diverse, not necessarily exclusively native.

Suburbia is very birdy

The conventional wisdom is that cities are inhospitable places for birds and other wildlife.  After all, haven’t we paved over much of their habitat, interrupted their movements by fragmenting their habitat, and drained or covered water resources? In fact, bird populations in urban areas all over the world are both plentiful and diverse.

After years of counting numerous bird species in his hometown of Seattle, the author of Subirdia wondered if Seattle might be unique because it is heavily forested.  After conducting similar surveys in 10 cities around the world, Marzluff is convinced that birds are successfully adapting to rapid urbanization of human society.  The urban centers of cities in North and Central America, New Zealand and Europe support an average of 23 bird species.  He found the least number of bird species (11) in Auckland, New Zealand and the greatest number (31) in St. Andrews, Scotland.

Starling in breeding plumage. Creative Commons - Share Alike
Starling in breeding plumage. Creative Commons – Share Alike

Another popular myth about the loss of bird diversity in the Anthropocene is that the globalization of human civilization produces “homogenized” nature.  That is, many people believe that bird populations may not be in decline, but there are a few hardy species that dominate everywhere.  Again, Marzluff’s studies do not corroborate that belief.  Five bird species are found in cities all over the world (house sparrows, starlings, Canadian geese, mallard ducks, and rock pigeons).  However, these ubiquitous species are not the predominant bird species he found in cities.  Of the 151 different bird species he found in the 10 cities he visited, 75% of them were unique to each of the cities.   “Homogenization is barely perceptible.” (1)

Comparing bird populations in cities with nature reserves

Marzluff also compared bird populations in cities with undeveloped nature preserves.  Once again, cities still look like good homes for birds.  He finds twice as many bird species in Ketchikan, Alaska as in the nearby wildlands along the Naha River, “a remote wilderness fifty miles away…that required powerboat, kayak, and hiking to attain.” (1)

He also visited Yellowstone National Park, a 2.2 million acre protected area within an undeveloped ecosystem of nearly 20 million acres, where he counted 26 bird species in four days.  From there, he flew to New York City where he counted 31 bird species in Central Park in only three days.  Historical records of bird surveys in Central Park and Yellowstone National Park indicate that about 200 bird species have been found in both parks since the late 19th century.  “From a bird’s perspective, a large park created by human hands or by nature is not all that different.”  (1)

Accommodating birds in cities

Marzluff’s concluding chapters advise city dwellers how to encourage and support birds.  His “ten commandments” for accommodating birds make no mention of planting native plants or eradicating non-native plants:

  • “Do not covet your neighbor’s lawn.”
  • “Keep your cat indoors.”*
  • “Make your windows more visible to birds that fly near them.”
  • “Do not light the night sky.”
  • “Provide food and nest boxes.”
  • “Do not kill native predators.”
  • “Foster a diversity of habitats and natural variability within landscapes.”
  • “Create safe passage across roads and highways.”
  • “Ensure that there are functional connections between land and water.”
  • Enjoy and bond with nature where you live, work, and play!”

Marzluff expresses a strong preference for native plants throughout his book, but his research in Seattle is inconsistent with that preference:  “The forests of Seattle and its suburbs now embrace 141 species of trees, including 30 native species and ornamentals from North and South America, Europe, Asia, and Africa.  Some are problematic invaders, but in total they provide a diverse menu of foods and nesting and roosting sites for birds.”  (1)

Why a preference for natives?

Garter snake in eucalyptus leaf litter. Courtesy Urban Wildness
Garter snake in eucalyptus leaf litter. Courtesy Urban Wildness

Another academic scientist in Washington State, Linda Chalker-Scott, directly addresses the vexing question of why public policies which mandate the use of native plants have proliferated despite the lack of evidence that they are superior in any way.  She focuses on this question:  “Do native and nonnative woody species differ in how they affect species diversity?”  Her literature search found 120 studies from 30 countries that quantified the biodiversity of birds, insects, mammals, reptiles, and other plants in woody plants and trees in urban landscapes.

The analysis of these studies reveals that “the science does not support the supposition that native plantings are required for biodiversity…it is clear that an automatic preference for native trees when planning in urban areas is not a science-based policy.” (2) The assumption that native plants are superior to non-native plants is based on these misconceptions:

  • The definitions of native and alien species are value judgments, not science-based concepts.
  • Native plants are often poorly suited to environmental conditions in urban areas, such as compacted soil and changes in the climate. Conversely, introduced plants are often well suited to these urban conditions.
  • Many introduced plants provide valuable ecological benefits. For example, they often provide food, pollen, and nectar resources during winter months when native plants are dormant.
  • Tropical milkweed is not native to California. (Asclepias curassavica) Creative Commons
    Tropical milkweed is not native to California. (Asclepias curassavica) Creative Commons

    Doug Tallamy is the academic scientist most closely associated with the native plant ideology. His claim that insects require native plants is based on his mistaken assignment of nativity to an entire genus, when only a few species within that genus are actually native.  For example, there are over 35 species of milkweed in the genus Asclepias, but only two species are native to California.  Most members of the milkweed family are useful to monarch butterflies.  It is therefore not accurate to claim that monarchs require native plants.  They have lived all over the world for over 200 years in some places where there are no native species of milkweed.

Chalker-Scott’s meta-analysis of 120 studies concurs with Mr. Marzluff:  “The published research overwhelmingly identifies diversity, structure, and function as the most important vegetation characteristics for enhancing community biodiversity…In fact, sometimes landscapes require the inclusion of exotic trees and control of natives to maintain diversity.” (2)

Doing more harm than good

Our readers know that we do not begrudge the preference of native plant advocates for native plants.  We encourage them to plant whatever they want.  We only ask that they stop destroying the plants they don’t like.  That request is based on our belief that they are doing far more harm to our public lands than any perceived benefit of native plants.  Much of that harm is caused by the widespread use of herbicides to destroy non-native vegetation.  These herbicides are known to damage the soil and they migrate in the soil, damaging neighboring plants that are not targeted.  These issues are surely a factor in the conspicuous lack of success of their “restorations.”  There is also mounting evidence of the toxicity of herbicides to bees, birds, and other animals including humans.

But there is another, equally important reason why we object to the futile attempts to eradicate non-native plants.  They are providing valuable habitat for wildlife.  Even when they are replaced by native plants after being destroyed, the animals that depended upon them are not necessarily restored to the landscape.  In fact, few projects plant natives after the eradication of non-natives.

Japanese honeysuckle. Attribution William Rafti
Japanese honeysuckle. Attribution William Rafti

A recently published study (3) of the removal of Amur honeysuckle (Lonicera maackii) is an example of the loss of valuable habitat.  The hypothesis of this study was that “invasion of urban habitats by exotic plants was the underlying mechanism driving changes in bird-plant networks.”  The study tested this hypothesis by comparing forest plots dominated by honeysuckle with those in which honeysuckle had been removed and the surrounding forest habitat replicated.  They measured nesting birds, nest predators, and nest survival.

They found that the lowest overall nest survival rates were found in the plots in which honeysuckle had been removed.  In other words, “…removal of invasive honeysuckle from urban forests did not restore network structure to that of rural landscapes.”  The authors concede, “This finding was not consistent with our original hypothesis that invasion of forests by the exotic Amur honeysuckle was responsible for the urban-associated changes in bird-plant networks.”  They conclude, “The degree to which native communities can be restored following removal of exotic plants remains unclear.” 

Actually, we think it is quite clear that eradicating non-native plants does not benefit man or beast. We marvel that the fantasy persists that there is some theoretical benefit to killing harmless plants, despite the consistent lack of evidence of any benefit and the considerable evidence of the harm of such attempts. 


*Like most ornithologists, Marzluff comes down hard on cats as killers of birds in his book.  However, he cites just one study about predation of fledglings.  The study used radio transmitters to determine the fate of 122 newly fledged birds over a period of two years.

The results do not justify the demonization of cats:  “Only 20 percent of radio-tagged birds died during our study.  Birds such as Cooper’s hawks and mammals such as Townsends’ chipmunks, ermine, and Douglas squirrels were the most likely predators.  The most notorious of all bird predators, the out-of-the-house cat, was implicated in only one death, though we could never be entirely sure which mammal or which bird had killed the fledging.”  (1) Marzluff credits a neighborhood coyote for controlling the cat population.  Frankly, that doesn’t make sense.  Chipmunks and squirrels are just as likely to be prey for the coyotes.

We have reported on similar studies which reach the same conclusions.  A meta-analysis of 8 studies of nest predators of song birds in North America used video cameras to identify the predators of 242 depredation events.  Only one of those nest predators was a cat.

We have no objection to the general advice to keep your cat indoors. (We have never had a cat and don’t plan to.)  However, we think that estimates of birds killed by cats are greatly exaggerated.  Humans seem to have an unfortunate desire to look for scapegoats and cats seem to fit the bill for bird lovers.

  1. John M. Marzluff, Welcome to Subirdia,” Yale University Press, 2014
  2. Linda Chalker-Scott, “Nonnative, Noninvasive Woody Species Can Enhance Urban Landscape Biodiversity,” Arboriculture & Urban Forestry, 2015, 41(4): 173-186
  3. Amanda D. Rodewald, et. al., “Does removal of invasives restore ecological networks? An experimental approach,” Biological Invasions, March 2015

Rosalie Edge, conservation hero

Rosalie EdgeWe are grateful to Dyana Furmansky for turning a suitcase full of letters into a fascinating biography of an important conservationist, Rosalie Edge. (1) Rosalie Edge was one of the first ardent defenders of wildlife—particularly birds—in America.  She came to this mission late in life, from unlikely previous experience.  Her life is therefore an interesting story, but it also interests us because her experiences as a conservationist shed light on our struggle to preserve our urban forest.  Specifically her struggle with the Audubon Society foretold our attempts to convince the local chapter of the Audubon Society (Golden Gate Audubon Society) that some of their policies are harmful to birds.

From privilege to the trenches of conservation warfare

Rosalie was born Mabel Rosalie Barrow in New York City in 1877 into a family of great wealth and privilege.  She married Charles Noel Edge in 1909 and followed him around the Orient for several years while he earned his living as a civil engineer and then as an investor.

They returned home, where Rosalie joined the woman’s suffrage movement in 1915.  She wrote passionate pamphlets for the suffragists, which later became her hallmark as a conservationist.   When women won the vote in the United States in 1920 with the passage of the 19th Amendment to the Constitution, Rosalie didn’t have much time to find another mission.   Her husband fell in love with another woman, effectively ending their marriage, which continued in name only to their death.

At the age of 44, in 1921, Rosalie was grief-stricken about the failure of her marriage.  She found solace in walks in Central Park in New York City and soon discovered that watching the birds gave her comfort.  The birders of Central Park were a community in the 1920s as they still are today.  They took Rosalie under their wing.  Soon she was embroiled in the organizational politics of the National Association of Audubon Societies (NAAS), the precursor to the National Audubon Society.  She learned that NAAS was engaged in activities that some members considered harmful to birds:

  • The President of the NAAS was taking donations from manufacturers of guns in exchange for adopting policies that were supportive of hunting birds.
  • NAAS also refused to oppose policies and practices that are harmful to birds, such as:
    • Killing birds to use their feathers in women’s hats, and
    • The policy of the federal government that paid large bounties for dead birds of prey, such as bald eagles.
  • NAAS was trapping and selling fur-bearing animals on its bird reserve in Louisiana to pay the salaries of their staff.

With only the force of her strong personality, Rosalie tried to shame the NAAS into abandoning these practices by attending their annual meetings.  When that approach failed, she sued NAAS for its mailing list and won.  With the mailing list of the 11,000 members of NAAS, Rosalie was able to communicate directly with the membership.  This approach put substantially more pressure on NAAS leadership as well as reduced its membership.   She had very little help with this effort.  She named her operation the Emergency Conservation Committee (ECC), but she was a proverbial one-woman-band.

Many of the NAAS policies to which Rosalie objected where eventually changed.  However, she was alienated from most members of NAAS and its successor NAS, until shortly before her death in 1962 at the age of 85.  She attended their banquet in 1962, along with 1,200 conservationists, where she was given a standing ovation.  Rosalie said, “’I have made peace with the National Audubon Society.’” (1)

The accomplishments of the Emergency Conservation Committee

The accomplishments of the ECC are particularly impressive if you keep in mind that most were achieved in the 1930s and 40s.  In the 1930s, there was very little money for anything other than creating jobs and putting food on the table.  In the 1940s the cost of World War II was our highest national priority.  Conservation was perceived as a luxury by both the public and the government.  Yet, Rosalie and those who helped her, accomplished many great things.

  • Migrating hawks shot in one day prior to establishing sanctuary.  Courtesy Hawk Mountain Sanctuary Archives
    Migrating hawks shot in one day prior to establishing sanctuary. Courtesy Hawk Mountain Sanctuary Archives

    Hawk Mountain in Pennsylvania was a place where wind currents funneled tens of thousands of hawks during their fall migration. It was therefore a popular place for hunters to stand on the mountain and shoot the birds out of the air.  Tens of thousands of hawks were slaughtered every year, which was just too much to bear for Rosalie.  Nearly penniless during the deepest years of the depression, Rosalie borrowed $500 from a friend with an interest in the hawks to lease Hawk Mountain.  Fortunately the land wasn’t useful for most purposes and economic conditions depressed land values, so she was eventually able to buy it.  It was the first privately acquired property for the sole purpose of conservation.  It was considered the model for The Nature Conservancy by one of TNC’s co-founders, Richard Pough.  Today, Hawk Mountain is visited by tens of thousands of visitors every fall to witness the migration.  There are far more visitors to see the birds than there had been to shoot them in the past.  The data gathered at the Hawk Mountain Sanctuary about immature hawk and eagle migration were very helpful to Rachel Carson in making her case against DDT.

  • When Franklin Roosevelt became President, things got a little easier for Rosalie because his Secretary of the Interior, Harold Ickes, shared her interest in conservation. Together they collaborated to create Olympic National Park in Washington State, to incorporate a sugar-pine forest into Yosemite National Park, and to create King’s Canyon National Park in the Sierra Nevada in California.  None of these achievements was easy.  The story of how opposition was overcome would sound familiar today.  Timber and other economic interests had to be satisfied or neutralized by overwhelming public support.  Rosalie’s passionate pamphlets were instrumental in creating public support.
Olympic National Park.  NPS photo
Olympic National Park. NPS photo

Familiar themes

Rosalie’s experiences with the National Association of Audubon Societies sound familiar to us.  Despite the organization’s stated mission of protecting birds, economic interests sometimes influence its policies and practices.  The paid staff of an organization is under constant pressure to fund its salaries.  The temptation for quid pro quo arrangements is great, particularly during hard economic times.  Although Rosalie was successful in ending such arrangements, the temptation is always there.  Therefore, constant vigilance is required to prevent it from happening again.

Towards the end of her life, Rosalie’s unpublished memoir explains why her Emergency Conservation Committee was successful:

“In her memoir, she had commended volunteerism as the most meaningful way to bring about change.  ‘I beg each one to keep conservation as his hobby, to keep his independence, his freedom to speak his mind,’ she had written years before.  She had seen too many professionals become jaded or fall captive to special interests.  She, on the other hand, had spoken freely.  There would always be a need for those who could do that, she warned.” (1)

We believe that the local chapter of the Audubon Society (Golden Gate Audubon Society) is supporting projects that are harmful to birds.  We have detailed those projects in a recent post and won’t repeat them here.  The story of Rosalie Edge’s confrontation with the National Association of Audubon Societies warns us that changing those policies will not be easy.  However, we are inspired by Rosalie’s success and we follow her lead:  We are a loose confederation of volunteers who work collaboratively, but independently.   We are compensated solely by the occasional success of our venture to save our urban forest and the animals that live in it.  We cannot be compromised by any economic interests.


(1) Dyana Z. Furmansky, Rosalie Edge Hawk of Mercy, University of Georgia Press, 2009

Open letter: Does Audubon Society advocate for birds or birders?

Our family was a member of the Audubon Society for decades because we love birds and birding all over the world is our primary hobby.  So, it was painful to give up that membership a few years ago when we were unable to convince the Bay Area chapter of Audubon (Golden Gate Audubon Society (GGAS)) that its support for the projects that are destroying hundreds of thousands of trees, are harmful to birds.  We didn’t give up easily.  We tried for many years to convince GGAS that their policy is harmful to birds.  Since leaving Audubon, the GGAS has become progressively more aggressive in its support for these projects.  Here are a few recent examples of policy decisions they have made:

  • GGAS signed a letter of support for the planned project that proposes to aerial bomb 1.3 metric tons of rodenticide on the Farallon Islands to kill mice.  You can read about that horrible project HERE.
  • GGAS is also supporting the US Fish & Wildlife project that is shooting barred owls based on the belief that another native bird will benefit.  Read about that project HERE.
  • Recently they sent a letter to University of California, San Francisco, asking them to proceed with their original plans to destroy approximately 30,000 trees on Mount Sutro.  These plans are presently on hold in response to the objections of the public.

Today, we are going to take a closer look at Audubon’s support for the destruction of most trees on Mount Sutro.  Jack Dumbacher, member of the GGAS Board of Directors and Chairman of the GGAS “Conservation” Committee, has written an article for the GGAS blog about that project, which gives us this opportunity.

Who are “WE?”

Mr. Dumbacher’s article begins with a litany of “what WE want:”

  •  “We understand that just seeing birds is not enough – we want diversity. It is not enough to have a life list of one species that you’ve seen really well.
  • We want a long life list with many species. We want to count as many species as we can on each field trip.
  • We want to see birds doing a variety of interesting things.
  • We want reasons to visit a variety of habitats and regions. And we love seeing that occasional rare, out-of-place species.”

Many birders and Audubon members have tried unsuccessfully to engage Mr. Dumbacher in a dialogue, so we are resorting to this “open letter” venue to ask these questions:

  • Who are “WE” in this list of what Mr. Dumbacher claims “WE want?”  Does he speak for you?  Does he speak for the birds?  If not, is he speaking for himself?  Is he speaking for all Audubon members?  If you are an Audubon member, is he speaking for you?
  • If this isn’t a list that speaks for you, what do YOU want?  Do you want to be able to walk in a forest in which many birds live now?  Or do you prefer grassland and dune scrub, which is what the forest in San Francisco is being converted to by native plant advocates?
  • If Mr. Dumbacher’s wish list doesn’t speak for the birds, what do you think the birds want?  Where do you think the owls and raptors will nest if all the tall trees are destroyed?  Where do you think the bats will live if the tall trees are destroyed?  What do you think the hummingbirds will eat in the winter if all the eucalypts that flower in the winter are destroyed?
Red-tailed hawk nesting in eucalyptus.  Courtesy urbanwildness.org
Red-tailed hawk nesting in eucalyptus. Courtesy urbanwildness.org

We are too ignorant to understand what THEY want

Mr. Dumbacher wonders how those who share his opinions regarding nature can convince us to want what they want:  “…how do we make the case for diversity?”  Then he proceeds to try to make the case, by looking back on his childhood experiences in nature and passing judgment on them: 

“My father spent much of his spare time in open green spaces. Sometimes I would go with him, and we heard birds and saw squirrels and geese, and we believed that we loved and understood nature. After spending many more years of my life studying biology, I realized that we were just golfers on a relatively impoverished golf course landscape.”

It struck us as unspeakably sad that he would look back on his childhood experience in nature with such condescension.  It seems that each of us should have the right to enter nature with whatever level of knowledge we can bring to that experience.  Mr. Dumbacher has a Ph.D. degree.  Does he think a Ph.D. degree is required to appreciate nature?  Such a prerequisite would leave most of us out.  Don’t we have a right to enjoy nature too?

Burdened with too much knowledge

Trilium in Virginia
Trilium in Virginia

We will use our personal experience to present a contrarian viewpoint.  A few years ago we had the opportunity to drive the length of the Blue Ridge Highway from the Shenandoah Valley in northern Virginia to the heart of Tennessee.  Of course, we had many walks in the woods.  It was early spring.  The dogwoods were blooming.  The birds were actively starting their nesting season.  As much as we enjoy a walk in the woods here in California, there was even greater pleasure in those walks in the eastern woods because we have almost no knowledge of what is native or non-native there.  It was a great relief to be able to walk without passing judgment, as we have been taught to do in California.  There was no need to point fingers and declare that something “doesn’t belong there.”  We could accept the beauty of everything we saw on equal terms.  Ignorance was bliss.

Dogwood, Virginia
Dogwood, Virginia

 

Monarch caterpillar on milkweed.  Tilden Botanical Garden
Monarch caterpillar on milkweed. Tilden Botanical Garden

We will contrast that experience with a more recent experience in the East Bay Regional Park District Botanical Garden in Tilden Park.  We were taking a course in which several participants in the class were members of the California Native Plant Society.  You might think that a botanical garden in which solely natives are planted, would be a pleasant place for them to walk.  It wasn’t.  They were outraged by the few non-native “weeds” we saw.  They crawled over the plantings to pull the uninvited plants from their roots.  One was a lovely scarlet pimpernel, blooming in its bright coral amongst native plants in their dormant, brown phase.   Their destructive attitude detracted from our enjoyment of the garden.

The “tiny minority” myth

As the “restoration” projects in the Bay Area have become progressively more destructive, the public has become progressively more opposed to them.   Mr. Dumbacher calls us a “vocal minority” in his article.  He is mistaken.  We consistently outnumber native plant advocates (sometimes ten to one) whenever we have an opportunity to express our opinion in a public venue:  in public hearings, on petitions, during written public comment periods.  We are not a minority.

Mr. Dumbacher is also mistaken in his description of the project which he is defending in his article.  He says, “…a Sutro Management Plan was formed that balanced incremental thinning with incremental planting of native species, in order to increase diversity and reduce the fire threat.”  We will give Mr. Dumbacher the benefit of the doubt by assuming that he has not read the Environmental Impact Report of February 2013, in which the project was described in detail.  Within a year five years, that project would have destroyed 90% of the trees (about 30,000 trees) and understory on 75% of the acres of Mount Sutro.  It proposed no planting of native plants, with the exception of a few small areas if money became available to pay for them.   The word “thinning” is used by native plant advocates to describe their plans to destroy the forest because it sounds less destructive.  However, it is not a word that accurately describes the destruction of 90% of the forest.

What happens to the birds that are there now?

Blackberries in the Sutro forest.  Courtesy Save Sutro Forest
Blackberries in the Sutro forest. Courtesy Save Sutro Forest

Unfortunately, we can’t share with our readers the lovely pictures in Mr. Dumbacher’s article because we don’t have permission, although you can visit the article to see for yourself.  You will see beautiful birds sitting on plants that exist now on Mount Sutro and Mount Davidson.  They are native plants that thrive in the understory of the forest and are unlikely to survive the devastation of the destruction of the trees and understory.  There are also non-native plants in the understory.  Many of them, such as blackberry, are valuable sources of food for birds.  There is no evidence, and no reason to believe, that destroying the Sutro forest will increase the number of bird species in San Francisco. 

Native red elderberry on Mount Sutro.  Courtesy Save Sutro Forest
Native red elderberry on Mount Sutro. Courtesy Save Sutro Forest

One wonders if Mr. Dumbacher isn’t aware of this obvious contradiction:  he illustrates his article with birds that live in the forest now while trying to make the case that the forest must be destroyed so he can see more birds.  Perhaps the answer is that he doesn’t really want more birds, he is only interested in certain birds:  “But If you want migrants to visit your city, if you want rare birds to breed in your local parks, and if you want a county list that exceeds 200 species, then please get involved in local habitat management and restoration, and be ready to speak up for nature in your city.”

The "managed" portion of the Sutro forest:  orange flags and weeds
The “managed” portion of the Sutro forest: orange flags and weeds

Here is another contradiction in Mr. Dumbacher’s appeal for your support for destroying most of the Sutro forest:  “we should try to manage a more natural forest.” In what sense is a “managed” forest also a “more natural” forest?  The Sutro forest is natural now, wild and unmanaged, a delightful mess.  We see no benefit in “managing” it.  Our experience with the managed summit of Mount Sutro is herbicide use (in the past), irrigation, wood chips, and dry weeds populated with colored flags where someone has apparently planted something that didn’t emerge from the wood chips.

Does Mr. Dumbacher speak for you?  Do you share his view of “nature?”

Postscript:  Mr. Dumbacher’s viewpoint is particularly troubling because he is Chair of the Department of Ornithology and Mammalogy at California Academy of Sciences, the Bay Area’s leading institution of science education.    It seems that there is little science in Mr. Dumbacher’s viewpoint as expressed in his article.

Nest Predation: Be skeptical of conventional wisdom

We have fond memories of the good old days when we could read the newspaper without questioning everything we read.  That was over 15 years ago, before we became engaged in our effort to save our urban forest from being needlessly destroyed because it is predominantly non-native.  Since then we have learned the uncomfortable lesson that it is necessary to be skeptical about every conventional belief about nature.  Today we will examine two such beliefs related to how birds are killed in nature.

Robin and chicks.  Courtesy SF Forest Alliance
Robin and chicks. Courtesy SF Forest Alliance

Cats are presumed to be the primary predator of birds

To illustrate how pervasive the belief is that cats kill birds, we start with an internet search, “cats kill birds.”  Here’s a selection of articles available on the internet that make that claim:

  • “Cats kill 3.7 billion birds annually”
  • “Outdoor cats kill between 1.4 billion and 3.7 billion birds a year”
  • “Cats kill more than one billion birds each year”
  • “Cats are Birds No. 1 Enemy, Study Says”

We have examined the specific claim about the number of birds killed by cats in an earlier post, so we won’t repeat it here.  Instead, we will tell you about a meta-analysis of 8 studies of nest predators of song birds in North America.  These studies used video cameras to identify the predators of 242 depredation events, that is, nests in which the eggs were destroyed or nestlings killed.  These studies were conducted all over North America in different vegetation types, such as forests, shrublands, and grasslands.   These studies report that these were the predators of the nests:

  • 88 mammals
  • 86 snakes
  • 52 birds
  • 16 insects

Only one of the 88 mammals was a domestic cat.  The detailed list of all 242 predators is fascinating reading, which we recommend to you.

We understand that nest predation is not the only cause of bird mortality.  However, most bird death occurs in the first year of life according to the Cornell Laboratory of Ornithology, so clearly nest predation is an important factor in bird mortality.  And if video cameras find virtually no evidence that cats are nest predators, then we must wonder if cats are the bird killers they are made out to be.

Like so many other assumptions of nature lovers, we wonder if people are misled by their personal experiences.  In this case, most people live in urban areas and there are probably more cats in urban areas, so it seems probable that people are more likely to witness bird-death-by-cat than snakes, for example.  But empirical studies suggest that we should not extrapolate from that personal experience to conclude that cats are responsible for most bird mortality.  We will reserve judgment on that question, although we encourage cat owners to keep their cats indoors.

Are cowbirds another scapegoat for bird death?

We have also reported earlier that cowbirds are scapegoated for declining populations of song birds.  Cowbirds are nest parasites, which means they lay their eggs in the nests of other species of birds.  Their chicks are often bigger than the chicks of other species so they out-compete them in the nest, which implies that cowbirds could reduce the reproductive success of other species of birds.  In fact, a study of a 30-year attempt to eradicate cowbirds did not find evidence that killing over 125,000 cowbirds increased the population of a rare songbird.

Yellow-billed Cuckoo.  NPS photo
Yellow-billed Cuckoo. NPS photo

Today we tell our readers about a study of another nest parasite, the cuckoo, which could explain why killing nest parasites does not benefit other species of birds.  The study of cuckoos was conducted over a 16-year period.  It did not find evidence that cuckoos were reducing the population of other species of birds.  The study hypothesizes that cuckoo chicks emit a foul-smelling substance that repels nest predators, thereby protecting its nest mates as well as the cuckoo from nest predators.  So, the disadvantage of the cuckoo chick competing for food with its nest-mates is counteracted by the protection the cuckoo chick confers on the nest.

Lessons we have learned

In the past 15 years, we have learned to be skeptical.  Here are a few lessons we have learned from questioning everything we read and hear about nature:

  • People seem to have a knee-jerk need to scapegoat someone or something without thinking carefully about the underlying causes of the problems we observe in nature.
  • When we hear a particular animal being blamed for a problem in nature, we turn to the scientific literature for verification to determine if there is any empirical evidence that supports that assessment.  We frequently find no evidence to support the conventional wisdom.  Sometimes we find evidence that contradicts the assumptions.
  • Even then, we must keep in mind that science is always moving forward.  Science only hypothesizes and every hypothesis must be repeatedly tested.  Hypotheses are often overturned as we learn more.
  • We do not think it is ethical to kill one animal based on the assumption that it will benefit another animal.  Aside from the presumption of deciding which animal is worthy of living, we think these projects are often mistaken in the assumption that a particular animal will benefit.  We believe that nature is far wiser than we are.

Are non-native plants “ecological traps” for birds?

One of the reasons why native plant advocates want the managers of our public lands to destroy non-native plants and replace them with native plants is that they believe native plants provide superior habitat for birds.  However, empirical studies do not support this belief, as we have explained in earlier posts.  Today we will examine an article recently published in an advocacy magazine, making the claim that non-native plants are “ecological traps” for birds:  “Nonnative Plants: Ecological Traps Offering alluring habitat for songbirds, exotic plants may actually decrease the animals’ long-term survival and fitness” (1)

Japanese honeysuckle.  Attribution William Rafti
Japanese honeysuckle. Attribution William Rafti

The article begins auspiciously with the good news that populations of some bird species have increased significantly in recent decades because of the spread of non-native plant species which are valuable sources of food:  “…a 2011 paper, published in the journal Diversity and Distributions, concluding that the number of fruit-eating birds such as cardinals, robins and catbirds tripled during the past three decades in parts of central Pennsylvania due to the spread of nonnative honeysuckles.”  (1)  And then the article attempts to contradict this good news by turning to the usual nativist caveats.

Generalists vs. Specialists

Nativists claim that the animal kingdom is divided into generalists and specialists.  The generalists are theoretically omnivores—they have a varied diet—and so depriving them of native plants will not prevent their survival.  Specialists, on the other hand, are dependent upon a narrow range of plant or animal species for survival.  We are expected to believe that specialists far outnumber generalists and that we doom them to extinction when one particular species of native plant or animal is unavailable to them.

Monarch butterfly caterpillar - Creative Commons - Share Alike
Monarch butterfly caterpillar – Creative Commons – Share Alike

Doug Tallamy is the purveyor of the generalist vs. specialist overstatement.  We have critiqued his assumptions in an earlier post.  In a nutshell, there are few mutually exclusive relationships in nature because they are a risky evolutionary strategy.  The plant or animal that is dependent upon one other species is significantly less likely to survive in the long term than an animal with more dietary options.  The perception that there are immutable relationships between insects and plants also underestimates the speed of adaptation and evolution, particularly of insects with large populations and short lifespans.

For example, a bird that eats insects usually eats all manner of insects as well as spiders.  They are not dependent solely upon caterpillars as Mr. Tallamy seems to believe:  “…warblers and chickadees rely on caterpillars for 90 percent of their diet during the breeding season, eating hundreds per day. ‘That’s a lot of insects,’ Tallamy says. ‘If you don’t have those insects, you don’t have the birds.’” (1)

According to Cornell Ornithology Lab–America’s most prestigious research institution for birds–warblers and chickadees have a much more varied diet than Mr. Tallamy believes.  (We chose specific species with ranges and abundant populations in Delaware where Mr. Tallamy lives.  However, the diet of all species of chickadees and warblers are similar.)

  • Black-capped Chickadee:  “In winter Black-capped Chickadees eat about half seeds, berries, and other plant matter, and half animal food (insects, spiders, suet, and sometimes fat and bits of meat from frozen carcasses). In spring, summer, and fall, insects, spiders, and other animal food make up 80-90 percent of their diet. At feeders they take mostly sunflower seeds, peanuts, suet, peanut butter, and mealworms.” (2)
  • Orange-crowned Warbler:  “insects and spiders.” (2) Most insects are not caterpillars and many are not herbivores.
Black-capped Chickadee - Creative Commons - Share Alike
Black-capped Chickadee – Creative Commons – Share Alike

No evidence that insects require native plants

Mr. Tallamy is focused on caterpillars because they are herbivores, that is, they eat plants.  Just as he believes that the birds need native plants, he also believes that plant-eating insects need native plants.  However, Mr. Tallamy disproved his own theory about an immutable relationship between native plants and insects when he supervised a graduate student whose thesis concluded: 

Erin [Reed] compared the amount of damage sucking and chewing insects made on the ornamental plants at six suburban properties landscaped primarily with species native to the area and six properties landscaped traditionally.  After two years of measurements Erin found that only a tiny percentage of leaves were damaged on either set of properties at the end of the season….Erin’s most important result, however, was that there was no statistical difference in the amount of damage on either landscape type.” (3)

This empirical study, supervised by Mr. Tallamy, was unable to find evidence that there are more plant-eating insects in a native garden than in a landscaped garden of non-native cultivars.  Yet, Mr. Tallamy continues to claim that insects require native plants and birds require those insects for their survival:  “Tallamy’s research shows that birds also may be harmed indirectly because nonnative plants affect insects. He has found that the number and diversity of plant-eating insects, especially caterpillars, drops dramatically when exotic plants invade…[Tallamy said,] ‘My prediction is that birds that specialize on insect herbivores will take a bigger hit than those that eat other insects,’” (1)

The study by Mr. Tallamy’s student about the relationship between native plants and insects is not the only empirical evidence that his assumption is incorrect.  We have published several articles about local studies that have found no such relationship:

Native plant advocates have also offered “evidence” of insect populations in the local eucalyptus forest.  UCSF produced a video to promote their original plan to destroy most of the eucalypts on Mount Sutro (now on hold indefinitely).  An arborist shows us eucalyptus leaves that have been chewed by insects.  He claims that a drastically thinned forest will be healthier because it will have fewer insect predators.  So, there are insects in the eucalyptus forest when it suits native plant advocates’ purposes and there are no insects in the eucalyptus forest when it does not.  They want more insects when they are advocating on behalf of birds and they want fewer insects when they are demanding that trees be destroyed.  It’s rather confusing.

Insects ARE important to birds

We agree with Mr. Tallamy that insects are very important to birds because they are a major source of food, especially during the nesting season when their high-protein content is vital to nestlings.  Therefore, we believe that Mr. Tallamy should join us in making climate change our highest environmental priority.  Because insects are cold-blooded, they are particularly vulnerable to the extreme weather conditions associated with climate change.  They cannot adjust their body temperature as warm-blooded animals can in response to such fluctuations in temperature.  A recent study predicts devastating consequences for insect populations in coming decades:  “Our predictions are that some species [of insects] would disappear entirely in the next few decades, even when they have a fairly wide distribution that currently covers hundreds of kilometers.” (4)

We believe that a single-minded focus on native plants is misguided because in a rapidly changing climate the entire concept of “native” becomes meaningless.  Just as insects are unlikely to survive radical changes in temperature, the ranges of native plants must change if species are to survive.

Stay tuned for Part II

In our next post, we will continue our critique of the article that theorizes that non-native plants are “ecological traps.”  We will tell our readers about the published research that contradicts statements in the article about predation of cardinal nests in non-native honeysuckle.  The author of one of the studies is quoted in this article, saying something completely different than her own published study.  It’s an intriguing contradiction.

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(1)    John Carey, “Nonnative Plants: Ecological Traps Offering alluring habitat for songbirds, exotic plants may actually decrease the animals’ long-term survival and fitness,” National Wildlife Federation, January 14, 2013

(2)    Cornell Ornithology Laboratory, Guide to Birds

(3)     Tallamy, Doug, “Flipping the Paradigm:  Landscapes that Welcome Wildlife,” chapter in Christopher, Thomas, The New American Landscape, Timber Press, 2011

(4)    “Extreme weather caused by climate change decides distribution of insects, study shows,”  Science Digest, February 20, 2014

No evidence that birds are harmed by non-native plants

The garden columnist of the San Francisco Chronicle wrote an article about the harmful effects of non-native plants on birds in 2012.  She quoted an ornithologist as making these gloomy predictions about the harm that non-native plants may be doing to birds:

  • “Nonnative berries may not provide the nutrition that particular native birds require.”
  • “Nonnative fruiting plants could bring birds into a wildland habitat new to them, not necessarily with a good outcome.  Birds might flock to a new area, feast on the new food source till it’s gone, but then not find enough food for so many birds in the rest of the habitat.”
  • “Nonnative plants alter wildland communities ‘in more complex ways than simply providing food for birds.’  A bird-dispersed nonnative fruiting shrub, for example, ‘can form underbrush or thickets in areas that previously lacked an understory…Birds may find their nesting sites disrupted, more cover for predators, etc.’”

Our initial reaction to these dire predictions was that they were entirely speculative.  The consistent use of the word “may” to describe the consequences of non-native plants suggested that supporting evidence was absent.  It seemed that, as usual, the nativist ideology was casting a dark pall on nature.

We were reminded of one of our first encounters with a nativist over 10 years ago.  On a tour of a park in San Francisco, he claimed that non-native plants in San Francisco were creating a “sink” which he defined as attracting migratory birds into a climate to which they were not adapted, where they would eventually freeze to death.  I pointed out to him that it does not freeze in San Francisco.  He was unaware of this fact.

Cedar waxwings in crab apple
Cedar waxwings in crab apple

Secondly, we reacted to the implication of the Chronicle article that birds are passive in nature and incapable of making good choices for themselves.  The suggestion is that birds are unable to discern nutritious food from “junk” food and incapable of choosing a safe nesting site to raise their young.

Thirdly, since every plant is native somewhere, we found the suggestion that non-native plants are nutritionally inferior to native plants illogical.  Are we to believe that where these plants are native, birds are malnourished?

Where is the evidence?

And so, we decided to see if we could find any actual evidence that supports these statements.  We started by looking at the research work of the ornithologist quoted by the Chronicle gardening columnist, Clare Aslan.  She earned her Ph.D. in Ecology at UC Davis in 2010.  Her Ph.D. project is described in a publication the year her degree was awarded:  “Avian use of introduced plants:  Ornithologist records illuminate interspecific associations and research needs.”  (1)

In this publication, Ms. Aslan tells us that her project was essentially a questionnaire that was sent to over 1,000 non-professional bird watchers in four American states (California, Florida, New York, and Washington).  These bird watchers were presumed to be skilled because they were members of Ornithological Societies of North America.  Responses were received from 173 of these bird watchers, of which 51% were from California.  Respondents reported 1,143 interactions between birds and plants.   “Interact” is defined as the full range of bird behavior:  eat, nest, perch, glean, etc.

The objectives of the questionnaire were:  (1) to evaluate patterns of bird use of non-native plants to determine the role the birds play in dispersal of “invasive” plants; (2) to examine the food web and guilds formed by bird interactions; and (3) to determine gaps in empirical research to inform future research efforts.

Robin and chicks.  Courtesy SF Forest Alliance
Robin and chicks. Courtesy SF Forest Alliance

Respondents to the survey reported that 47% of observations of feeding by 139 bird species were of seeds or fruits of non-native plants.  Thirty-five percent of all “habitat interactions” were with non-native plants and 26% of all nesting activity was in non-native plants.  If non-native plants are harming the birds, nearly half of them must be in danger of starving to death!

Ms. Aslan tells us nothing about the relative nutritional value of non-native plants compared to native plants in this publication.  In her concluding paragraph, she suggests that her primary finding is that more research is needed to understand the role that birds play in the dispersal of “invasive” plants which has “direct application for invasion prevention.” 

Perhaps Ms. Aslan was misquoted by the Chronicle garden columnist.  If not, Ms. Aslan does not seem to have any empirical evidence to support her statements about the negative impact of non-native plants on birds.

Research about birds’ food preferences

Million Trees is always looking for the happy ending.  Consequently, our next step was to search the scientific literature for evidence that birds are being harmed by non-native plants.  It was not difficult to find several reassuring articles about the food preferences of birds:

  • One study found that birds do, indeed, have food preferences and their preferences are based on many factors, including color, size, and availability.  However, “In addition to these factors the nutritional composition of fruit pulp also influences selection of fruits by birds.”  (2)
  • Another study found that what birds choose to eat depends somewhat on their migratory patterns.  They choose foods with more fat content immediately prior to a long migratory journey over “major ecological barriers” such as seas and deserts. (3)
  • In a native eastern forest in the United States, most of the nutritionally best fruit was eaten early in the season, prior to the beginning of the migration.  Over-wintering birds were then left to eat the fruit that remained.  (4)
  • Finally, a study of fruit in the tropics showed that fruit that is more conspicuously colored and/or displayed seemed to be compensating for lower nutritional value than less conspicuous fruit.  The authors speculate that these are the evolutionary trade-offs that enable plant species to survive. (5)

All of these studies suggest that the birds know what they are eating and why.  We find no reason to fret on behalf of the birds that are eating non-native seeds and berries.  In fact, the eradication of some of the best food sources—such as Himalayan blackberries—may be a greater cause for concern.  And, once again, we find the extreme negativity of nativism to be a bigger problem, with respect to the damage being done to the environment in the guise of saving the planet from the harm they have imagined.

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(1)    Clare Aslan and Marcel Rejmanek, “Avian use of introduced plants:  Ornithologist records illuminate interspecific associations and research needs,” Ecological Applications, 20(4), 2010.

(2)    E.W. Stiles, “The influence of pulp-lipids on fruit preference for birds,” Vegetatio, Volume 107-108, Issue 1, 1993

(3)    F. Bairlein, “Nutrition and Fruit Selection in Migratory Birds,” Bird Migration, Springer Berlin Heidelberg, 1990

(4)    John W. Baird, “The Selection and Use of Fruit by Birds in an Eastern Forest,” The Wilson Bulletin, Vol 92, No 1, March 1980

(5)    Nataniel Wheelwright and Charles Janson, “Colors of Fruit Displays of Bird-Dispersed Plants in Two Tropical Forests,” The American Naturalist, Vol. 126, No 6, December 1985

The Natural Areas Program harms wildlife by violating its Streambed Alteration Permit

It’s spring.  Have you noticed that the birds are singing?  This is the time of year when they are most vocal.  They are staking out their nesting sites and attracting their mates with their songs.  They are quieter when they have laid their eggs as they try to avoid detection.  Migratory birds are also passing through, on their way to their breeding homes.  The food they find along the way is important to their survival on their long and physically challenging journeys from their winter to their summer homes.

Subscribers to Wildcare recently received an email newsletter reminding them that pruning trees and shrubs at this time of year is dangerous for the birds that are hiding their nests in them.  Wildcare is a local organization which treats sick or injured animals and educates the public about “how to live peacefully with wildlife.” 

Hummingbird nest in Pittosporum, March 2012

We were recently reminded of the vulnerability of birds at this time of year in our own yard when a hummingbird selected our flowering, non-native Victorian Box tree (Pittosporum undulatum) to build her nest.  Her nest was completely invisible to us, but we spotted her darting in and out of it as she built her nest.  We were able to take this picture of her sitting on her nest by crawling into the understory of the tree.

Hummingbird nest is not much bigger than a quarter!

Then disaster struck.  An early spring storm tore a huge branch from the tree and sent her nest tumbling to the ground.  We watched with heavy hearts while the hummingbird made anxious, noisy flights into the fallen branch.  When she gave up, we carefully lifted the fallen branch to find her tiny, empty nest.  As sad as this event was in our lives and hers, at least we knew that the failure of her nest was no fault of ours.   San Francisco’s Natural Areas Program cannot say the same of their destructive project in Glen Canyon Park.

The Natural Areas Program violates their Streambed Alteration Permit

Destroying vegetation with chainsaws in Glen Canyon Park, November 2011

The Natural Areas Program began to destroy the non-native vegetation in Glen Canyon Park in San Francisco in November 2011.  In addition to destroying valuable habitat with chainsaws, they also sprayed herbicides.  The San Francisco Forest Alliance (SFFA) protested this destructive project many times but it has continued unabated to as recently as April 27, 2012, when they pruned trees and sprayed herbicides.

Earlier in April, SFFA learned from a public records request that this project violated a legal commitment to the California Department of Fish & Game.  The Natural Areas Program made the following commitment to mitigate harm to wildlife in Glen Canyon Park in its Streambed Alteration Permit:

It is the policy of RPD’s Natural Areas Program that no new projects will begin during the breeding season (December to May).  Follow up work in previously cleared areas may be done during the breeding season, however, because areas will have been cleared previously. Wildlife will not likely be using these areas for breeding.  This protocol has been effective in reducing impacts to breeding wildlife.”

SFFA brought this violation of its commitment to the attention of the General Manager of the Recreation and Park Department immediately.  The head of the Natural Areas Program said that the violation was necessary because the grant funding for the project was about to expire.  To avoid losing the funding for the project, the birds and animals of Glen Canyon Park were subjected to this destructive project during their breeding and nesting season. 

SFFA has brought this violation to the attention of the California Department of Fish & Game.  Their regulations require them to enforce the terms of the Streambed Alteration Permit, including the mitigation of potential harm to wildlife.  Violations of the terms of the permit are subject to “civil penalties” according to the regulations:  “A person who violates this chapter is subject to a civil penalty of not more than twenty-five thousand dollars ($25,000) for each violation.” 

One month after SFFA informed California Department of Fish & Game of the violation, nothing seems to be done about it.  In fact, weeks after SFFA sent this information to Fish & Game, another episode of destruction occurred in Glen Canyon Park on April 27, 2012.

The consequences of native plant “restorations” to wildlife

We will never know how many birds and animals were harmed by the destruction in Glen Canyon Park.  The management plan for the Natural Areas Program tells us (Appendix D) there are 18 species of birds that are found in and/or breed in Glen Canyon Park that are considered “Species of Local Concern.”  That is, the Audubon Society considers them rare in San Francisco. 

We also know that migratory birds will find less food in Glen Canyon Park this year than they have found in the past as they pass through San Francisco on their way to their breeding homes.  Many of the flowering and berry producing non-native plants that have thrived in Glen Canyon Park in the past have been destroyed by this destructive project, which is described by the Natural Areas Program in its Streambed Alteration Permit application as “…the ‘Scorched Earth’ method, in which all above-ground vegetation including natives, are removed.”  

Ironically, this project was partially funded by a grant program of the State of California entitled “Habitat Conservation Fund.”  We believe this project was a grotesque misuse of this fund.  The wildlife of Glen Canyon Park did not benefit from this project.  In fact, we believe they have been harmed by it.

The Sparrow Wars: America’s first “invasive species”

The public’s mania about “invasive species” often seems new to us.  It’s not.  In Peter Coates’ provocative book, American Perceptions of Immigrant and Invasive Species, we learn about one of the first episodes of public concern about an introduced species in American history, known as the “sparrow wars.”

English sparrow. US Fish & Wildlife photo

Like many introductions of non-native species of plants and animals, the English sparrow (AKA house sparrow) was introduced to perform a practical function.  Elm trees on the East Coast were being defoliated by a voracious native caterpillar.  In 1852, The English sparrow was brought to America to rescue the trees from the caterpillars.  The sparrows thrived and were soon reviled by ornithologists who considered them alien invaders.

The debate between ornithologists and those with a more cosmopolitan view of nature is reported at length by Coates.  Long story short, the debate is reminiscent of what we hear today from nativists:

  • They feared that the English sparrow would compete with native species for food and habitat and that native species would lose this competition.
  • They considered native birds superior to the English sparrow which was considered dirty and a promiscuous breeder.
  • The English sparrows were city dwellers and were considered the bird equivalent of ghettoized immigrants.
  • The English sparrows were criticized for not eating enough of the caterpillars they were imported to eat.  They weren’t doing the job they were hired to do!

This debate raged on amongst birders for decades according to the historical record reported by Coates.  However, we no longer hear birders complain about the English sparrow, although we hear them complain about many other birds.

Update:  This post requires an update.  The New York Times published an op-ed in which a woman describes in horrific detail the monomaniacal attempts of her mother to exterminate all house sparrows in their neighborhood based on her belief that their eradication would benefit blue birds.  It is a blood-curdling story that contradicts my naïve belief that after nearly 200 years, the house sparrow has been accepted in America. 

Modern equivalents of the “sparrow wars”

Cherry-headed conure. Attribution: Share Alike

Birders in San Francisco are currently complaining about the cherry-headed conures, more commonly known as the parrots of Telegraph Hill.  They believe the parrots are depriving native birds of food and nesting places.  They object to their presence in a place where they “don’t belong.”

We were introduced to this mindset by an ominous encounter with a birder in Florida who is typical of the nativist viewpoint of the avian world.  The sound of gunfire drew us to a man with a shot gun on the lawn of our motel.  Starlings were falling around him, where he quickly finished them off with a vigorous stomp of his booted foot.  We were unfamiliar with the hatred of non-native species at that time and asked him why he was killing the birds.  He seemed stunned to be questioned.  He explained, as though speaking to retarded children, that the starlings were “trash birds” that must be killed.  Following a basic rule of survival, we walked away from a person wielding a gun.

Why was the English sparrow redeemed?

Returning to the English sparrow, why are they no longer the target of hostility from  birders?  We speculate that one reason may be that they have been here for a long time, nearly 200 years.  Just as human immigrants are often the target of prejudice and discrimination when they first arrive, they eventually become a routine part of our world.  We rarely think of the Irish or other Europeans as immigrants in America.

Another reason is that the population of English sparrows is actually declining:  “Since 1966 its North American population has declined by 2.5 percent annually.” (1) However, there is still an estimated population of 150 million in North America.

Ironically, the population of English sparrows is declining significantly in Britain, its ancestral home, where only 13 million are estimated to remain.  In 2000 the British press was full of stories about the sudden decline of their iconic bird, “Responding to the strong sense that an essential part of the nation’s natural heritage…was disappearing…”

The lessons of the sparrow wars

These are familiar themes to the readers of the Million Trees blog:

  • Some people fear newcomers to their world, whether those newcomers are people, animals or plants and that fear can result in destructive hatred.
  • Newcomers usually fit in eventually.  What is initially perceived as a threatening “invasion” rarely turns out to be a problem in the long run.
  • Because nature is dynamic, the new home of an introduced species sometimes becomes the only home of that species.  The movement of species is another way to ensure their survival.  In fact, there is a new movement amongst citizen “scientists” to move rare species which are threatened by changed climate conditions into new locations.  This is called “assisted migration.” (2)

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(1) Peter Coates, American Perceptions of Immigrants and Invasive Species, UC Press, 2007.  All quotes are from this book.

(2) Emma Marris, Rambunctious Garden, Bloomsbury, 2011.

New Orleans: A case study in the resilience of nature

In August 2005, the city of New Orleans was hit by a devastating hurricane, dubbed Katrina, and a subsequent storm surge that destroyed much of the city and killed many of its residents.  The Lower Ninth Ward of New Orleans was one of the hardest hit areas of the city because it was the location of two breaks in the levee and is also at a lower elevation than less damaged neighborhoods.

The population of New Orleans reached its peak of 627,525 in 1960.  A year after Katrina, the city’s population had plummeted to about 200,000.  Six and one-half years later, the population is estimated to be 356,000. 

Neither the loss of population nor the return was spread evenly throughout the city.  The Lower Ninth Ward lost 75% of its population since 2000 because the damage was greatest there and its previous inhabitants did not have the resources to restore their properties.  For the same reasons, there are few services in the Lower Ninth Ward, such as a supermarket, or a police or fire station, making it a less attractive place to live.

Andry St & North Galvez St, New Orleans

The New York Times Magazine recently published a feature about the Lower Ninth Ward aptly entitled, “Jungleland.”  The article reports that nature has returned to the Lower Ninth Ward of New Orleans without the help of man and now resembles a dense jungle, more heavily populated by animals than people. 

Nature returns to the Lower Ninth Ward

The Lower Ninth Ward is a case study in the resilience of nature.  It is being intensively studied by ecologists as an example of how nature recovers from natural disasters, such as the volcanic eruption of Mount St. Helens and the earthquake and tsunami in Japan one year ago.  What all these disasters have in common is that they wiped the ecological slate clean.  Everything growing and living in these places was swept away to bare ground.

The Lower Ninth Ward was built on fertile ground because it was the repository of sediment from the Mississippi River for millennia before it was protected by levees and built upon.  This is also a part of the country that enjoys a warm climate and plenty of rain.  These factors undoubtedly contributed to the robust and rapid regrowth of vegetation in the Lower Ninth Ward.

The regrowth is almost entirely non-native.   Before the land was cleared for plantations in the mid-1700s the native vegetation was reeds and brambles along the river, hardwood forest behind the river, giving way to cypress and palmetto swamp in the interior.  “Today there are few species native to the land, other than several kinds of sedge and aquatic grass.  Only a handful of palm, live oak, and bald cypress survived the storm.” * 

North Robertson St., New Orleans

The current vegetation is described as: “A variety of species, some exotic, have moved in, among them crepe myrtle, black willow, and golden rain trees laced with vines.  The undergrowth is a chaotic mix of weeds as high as basketball hoops, and flowering shrubs like lantana, oleander and oxalis.”     

Last fall, the city of New Orleans launched a new campaign to reclaim the Lower Ninth Ward.  The city engaged a crew to clear the vacant lots of trash and vegetation in an effort to make the neighborhood more attractive to potential homeowners and investors.  At the rate of 20 lots per day, it takes the crew three months to clear the vegetation.  Then they begin again, because within three months the vigorous vegetation has reclaimed the vacant lots.

Birds return to the Lower Ninth Ward

An ornithologist from the University of New Orleans visited the Lower Ninth Ward with the author of the Times article.  He was permitted to visit the area for the first time one month after the storm, when attempts to find residents who hadn’t survived the storm were considered complete.  At that time he reported complete silence.  There was no birdsong in the Lower Ninth Ward. 

The birds that were common before the storm, such as mourning doves and house sparrows, are slowly beginning to return in small numbers.  There was a significant increase in the population of raptors, such as hawks, falcons, and shrikes.  The ornithologist speculated that an increase in the rodent population was responsible for this increased population of raptors, which he described as “supernatural.” 

The ornithologist accompanying the journalist waded into thickets covering several vacant properties, “pishing” as birders do to attract the birds to them.  We will let the ornithologist speak for himself as he rapturously reports to the journalist the many birds he sees and hears:

“’’I’ve gone whole winters without seeing a field sparrow in the New Orleans vicinity.  Field sparrows, swamp sparrows, simply do not winter in residential New Orleans…Orange-crowned warbler!’ He shouted back at me. ‘Ruby-crowned kinglet!’”

Ruby-crowned kinglet

The journalist following the ornithologist couldn’t keep up:  “It was no longer possible to distinguish which calls were his and which the birds’.  He walked around a stand of 15-foot Chinese tallow trees, the green and crimson leaves waving mournfully in the wind.  And then he was gone.  The wilderness just swallowed him up.”   

Lessons learned in New Orleans

The recovery of nature in New Orleans is an ecological experiment that was not fabricated by scientists. Man did not manipulate the outcome.  And this is what nature is telling us:

  • Native plants do not magically return when existing vegetation is wiped clean to bare ground
  • Birds do not care if the vegetation is native or non-native.  They will inhabit either.
  • Since the diet of many birds is predominantly insects, we should assume that the insects have also returned to the Lower Ninth Ward and that they are feeding on non-native vegetation.

These lessons are not consistent with the native plant ideology which equates the existence of non-native plants with “ecological collapse.”  Nature is thriving in New Orleans without the benefit of native vegetation.

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* Nathaniel Rich, “Jungleland,” New York Times Magazine, March 25, 2012.  All quotes from this article

Eradicating non-native plants is taking the food out of the mouths of birds

Plants have many different strategies to ensure their reproductive success.  Sometimes they are passive participants in their propagation.  Charles Darwin studied the dispersal of the seeds of plants and reported a particularly stunning example:  “He raised more than eighty plants from the mud-ball gathered round a wounded French partridge’s leg.”*  He also raised plants from seeds found in the stomachs of birds, which brings us to today’s topic:  the non-native plants which are eaten by birds are categorized as “invasive” plants and are therefore doomed to be eradicated.

We often puzzle over the list of nearly 200 non-native plants on the list compiled by the California Invasive Plant Council (Update:  Now nearly 300 in 2020).  We know from horticultural experience and scientific studies that at least two of the trees on this list are not invasive.  Aerial photographs of open space in the Bay Area taken over a period of 60 to 80 years, proves that neither the eucalyptus nor the Monterey pine forests are spreading. 

Cotoneaster lacteus. Jackson Nursery, UK

There are also several species of non-native shrubs which produce berries on the list of “invasive” plants that we know don’t spread in our gardens:  English holly trees, Cotoneaster, and Pyracantha.  So, why are they on the hit list?  The garden columnist in the San Francisco Chronicle recently told us why in answer to a question about planting a non-native holly tree for Christmas foliage in the garden:

Berries are a little harder to come by if we follow the advice of native plant specialists who are concerned about escape of holly, cotoneaster and pyracantha into nearby wildlands, particularly in coastal counties. Birds that eat the fruit and deposit seeds are the culprits.” 

Pyracantha. Wikimedia Commons

In other words, native plant advocates don’t want gardeners to plant non-native plants that produce berries that birds eat because they don’t want the plants to spread.  Obviously, their dedication to native plants trumps whatever concern or interest they might have in the welfare of birds.  Native plant advocates frequently claim that their “restorations” will benefit wildlife.  Clearly the eradication of berry-producing shrubs does not qualify for such a claim.

The loss of food and habitat for the wildlife that lives in our public lands is only one of many issues in the debate about native plant “restorations.”  But for bird lovers, this is a high priority.  In this regard, we were struck by one of the public comments that was recently submitted on the Draft Environmental Impact Report for the Natural Areas Program.  This self-identified “birder” said this about the radical “restorations” in San Francisco:

“Restoration areas such as Land’s End, El Polin Spring, Crissy Field are seldom spoken about anymore by birders or others looking for populations of wildlife.  Since the vast majority of the city’s resident bird species feed, roost and breed in trees, they leave, starve or are predated when their habitat is destroyed.”

Cedar Waxwings in crab apple tree. Wikimedia Commons

As the Cedar Waxwings pass through the Bay Area on their annual migration, we see them eating the berries in our holly tree.  They remind us that the eradication of non-native trees benefits neither animals nor birds, nor insects.  Who benefits from these destructive projects besides the people making their living at it?  It’s a mystery.


* Mabey, Richard, Weeds:  In Defense of Nature’s Most Unloved Plants, HarperCollins, 2010, page 29