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Wild WNY / Bird populations plummet

Low counts for many familiar species



Cerulean warbler

 

Ever since I began writing natural history columns in the 1990s, I’ve received phone calls and letters complaining about “the lack of birds.” A typical comment: “I don’t understand it. Until last year, I had dozens of birds visiting my feeders. Now all I have to keep me company are a few house sparrows and squirrels.”

 

I never took those messages as seriously as I should have. I usually responded that our local records showed little decline in most of the feeder-visiting species these readers were missing and sometimes I even offered such nonsense as: “Perhaps a new neighbor has set out a more attractive feeder or is offering more expensive food.”

 

But over time, my birdwatching friends and I also noticed a decline in the population of many species. Most evident in their near-absence were birds of meadows and meadow-edges. Very common species in the past—bobolinks, meadowlarks, brown thrashers, and indigo buntings—became harder and harder to find. Sparrows I had seen or heard in most open fields were now missing from counts; savannah, field, vesper, and grasshopper sparrows became rare and Henslow’s sparrows disappeared from this region entirely.

 

Now, an important report in this nation’s leading scientific journal, Science, by Kenneth Rosenberg and ten other researchers, not only confirms these observations but speaks to broader implications as well. The article’s ten pages of text, tables, and graphs spells out a harrowing picture, summarized in the article abstract:

 

Species extinctions have defined the global biodiversity crisis, but extinction begins with loss in abundance of individuals that can result in compositional and functional changes of ecosystems. Using multiple and independent monitoring networks, we report population losses across much of the North American avifauna over 48 years, including once common species and from most biomes. Integration of range-wide population trajectories and size estimates indicates a net loss approaching 3 billion birds, or 29% of 1970 abundance. A continent-wide weather radar network also reveals a similarly steep decline in biomass passage of migrating birds over a recent 10-year period. This loss of bird abundance signals an urgent need to address threats to avert future avifaunal collapse and associated loss of ecosystem integrity, function and services.

 

That loss of three out of every ten birds is not, as you might expect, the same for all kinds of birds. In particular, our observations of loss among meadow birds are confirmed: they are down to half their population a half-century ago and sparrows alone make up a quarter of the three billion bird decline. If you add warblers, blackbirds, larks, finches, and swallows, that accounts for ninety percent of the bird loss. And it should be noted that even house sparrows and starlings have lost numbers. (Meanwhile in Great Britain, house sparrow numbers are so bad that ornithologists are seriously concerned.)

 

But the decline is uneven. While 491 species are losers, 100 others have gained in population. Some of those winners even non-birders will recognize: turkeys, grouse, raptors, ducks, and geese. (If we could trade a few of those lawn-destroying Canada geese for their weight in warblers, we would be far better off.)

 

Home feeders attract mostly woodland species and the report confirms those losses as well. Eastern forest birds like chickadees, woodpeckers, and nuthatches are down almost twenty percent, and boreal forest birds that retreat during winters when food crops are down in the north—redpolls, siskins, grosbeaks, and crossbills—are down over thirty percent.

 

Going beyond avian species, the report warns, “Given that birds are among the best monitored animal groups, birds may also represent the tip of the iceberg, indicating similar or greater losses in other taxonomic groups.”

 

Causes

Although the Science report does not directly address the causes of the decline, it does mention a few obvious possibilities: habitat loss, use of toxic pesticides, agricultural intensification, urbanization, and climate change. Anthropogenic mortality is also listed—that tongue-twister represents direct human-related causes, including cars, buildings (especially building windows), communication towers, and wind turbines.

 

Of course, single-issue proponents will cite their own favorite among them. Locally, for example, this study is prime material for arguments against erecting new wind turbines, never mind that another major study by Loss, Will, and Marra indicates that feral and wandering pet house cats kill hundreds of times the number of birds killed by turbines.

 

I suggest a cause that I never see represented. It is our love affair with raptors. Until the late twentieth century, thousands of hawks were killed as they migrated north along mountain ridges. Those hawk kills were stopped and, subsequently, their numbers have increased. Whereas I certainly do not call for removal of hawks from the list of protected birds, I think that we should recognize that their increase has had a balancing effect on the number of birds on which they prey.

 

What you can do

As the report states, “Population declines can be reversed, as evidenced by the remarkable recovery of waterfowl populations under adaptive harvest management and the associated allocation of billions of dollars devoted to wetland protection and restoration, providing a model for proactive conservation in other widespread native habitats such as grasslands.”

 

There are things we can do as individuals to address this serious problem. Here are the seven suggestions modified from one list:

 

1. Learn how to make your home and office windows safer from bird collisions.

2. Keep cats indoors.

3. Introduce native plants and reduce your lawn area.

4. Avoid pesticides.

5. Drink shade-grown coffee.

6. Use less plastic.

7. Share your bird observations.

 

I add one more recommendation to those readers who are active in politics: consider this problem in preparing regulations regarding the preservation of parklands and land use development.

 

 

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