Tuesday, May 24, 2011

losing our common farmland birds: the Barn Swallow

this photo of the Barn Swallow courtesy of Creative Commons

A bird that has pooped on every rural doorstep from Nova Scotia to Vancouver Island is now a threatened species in Canada. Earlier this month, COSEWIC (Committee on the Status of Endangered Wildlife in Canada) met in Charlottetown, PEI to assess the conservation status of 40 Canadian wildlife species. Up for discussion amongst several fishes, molluscs, insects, whales and amphibians, was a bird that every Canadian farmer knows, the Barn Swallow. Why designate a species that still seems very common? The short answer is because its numbers have fallen by as much as 76% in the past 40 years. If that continues the bird that gives the meaning to "swallowtail" will be all but gone by mid-century.

In my mind, this designation of one of the continent's most numerous and widespread birds is a sign that we have left the initial phase of bird decline and entered a new era. In general (there are exceptions) most of the species on COSEWICs list have had rather narrow niches and restricted breeding ranges making them particularly vulnerable. It's one thing to list a long-billed murrelet or a sage thrasher, because we don't have a lot of old growth Douglas Fir or Silver Sage habitat left. But we know we have reached another level of ecological dysfunction when we start listing the adaptive birds that have become habituated to our disturbed agricultural landscapes.

Here is the "Reason for Designation" from COSEWIC's database:

This is one of the world’s most widespread and common landbird species. However, like many other species of birds that specialize on a diet of flying insects, this species has experienced very large declines that began somewhat inexplicably in the mid to late 1980s in Canada. Its Canadian distribution and abundance may still be greater than prior to European settlement, owing to the species’ ability to adapt to nesting in a variety of artificial structures (barns, bridges, etc.) and to exploit foraging opportunities in open, human-modified, rural landscapes. While there have been losses in the amount of some important types of artificial nest sites (e.g., open barns) and in the amount of foraging habitat in open agricultural areas in some parts of Canada, the causes of the recent population decline are not well understood. The magnitude and geographic extent of the decline are cause for conservation concern.

There are undoubtedly many things behind the decline of this and other aerial insectivores (the Common Nighthawk, the other swallows and swifts, and many flycatchers), but the common denominator here is the food they eat: flying insects. The one insect we pay attention to, the European Honeybee, has experienced alarming declines in many areas of the continent in recent years. No one does Breeding Insect Surveys the way we have been doing Breeding Bird Surveys for more than forty years, so we have no baseline from which to measure the populations of our bugs. It seems a fair guess, given our ongoing toxification of soils, air, and waterways, that the chemical compounds we make and release into the environment--many of them specifically designed to kill insects--are affecting the breeding cycles and abundance of the creatures our insectivorous birds depend on.

Bird Studies Canada's Director of National Programs, Jon McCracken, wrote about this three years ago in a BSC newsletter. Jon does a fine job of presenting the alarming data and then discussing the whole range of possible factors contributing to the decline of our aerial insectivors. Not a happy read but it helps you understand why a bird like the Barn Swallow is now on COSEWIC's roster.

I had a very brief chance to talk to Jon when I was visiting Ontario two weeks ago, at a talk I gave in Simcoe for the Norfolk Field Naturalists. I was delighted to meet Jon and the other BSC folks who made the drive from Port Rowan to come out for the event. If there is any hope in these dark days for our birds and biodiversity it is in the people working for NGOs like Bird Studies and others across Canada. They are doing all they can to protect the birds and the integrity of their habitats and to educate the rest of us. We have to do our part and heed the warnings that the Barn Swallow and other common birds send our way.

Eastern Kingbird on a pasture near Cherry Lake--another common aerial insectivore in Canadian farmland that is declining each year.



    Hope. That the soup kitchen
    on 39th and Fillmore will be open.
    Across the street an old man
    preaches the end of the earth
    is near. He may be right.
    Hopelessness? No birds in this poem
    Nothing in here but hunger.
    People on the street look away,
    they won't read a homelss poem.
    The canary in the cave has turned
    into the common Barn Swallow,
    it's dazzling flight over trees,
    under bridges. The sky its
    It's starving to death. No more
    As the poet from Ohio said in 1977,
    "It turns out/You can kill them.
    It turns out/You can make the earth
    absolutely clean."

    Tom Crawford

  2. Thanks for that powerful poem. I could not tell from the identity whether you are quoting Tom Crawford or whether you are the poet himself. Either way, I appreciated receiving such a lyrical response.

  3. I live on vancouver island west of shawnigan lake and until last spring used to receive two pairs of barn swallows and send back fourteen.
    last spring and this spring have been cold , wet and very late, there are hardly any insects anymore, not even enough for hummmingbirds, I used to have hirty or more , the last two springs i have had three or four only. Is there any way to attract more of these two species,perhaps with alternate food such as dried insects that could be defrosted ?

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