Saturday, April 25, 2015

Why habitat matters: the flight of a long-billed curlew

Long-billed Curlew (image courtesy of Hamilton Greenwood)

If there is a voice of wildness on the high plains of Canada’s last native grasslands, it drifts from hillside to swale in the cry of the long-billed curlew.

You are out walking through the river breaks or hills in the Missouri Coteau, and the wind suddenly resolves into a low, melancholy  whistle that breaks  and rises, shifting into a bubbling rapid set of notes that makes you look up to the horizon. And there it is—something big flying in apparent agitation straight at you with its long down-curved bill agape, and you wonder for a moment if it will turn away before it knocks you down. It gives its cry once more and then turns away just before you think to duck.

There is a curlew nest somewhere hidden in the speargrass and, as a large intruder, you are not particularly welcome. But an intimidating nest defence has not been enough to protect Canada’s long-billed curlews from declining along with the rest of the birds that depend on native grassland for survival.

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) lists the long-billed curlew in its “special concern” category, for though its decline has not been as marked as other grassland species, its range has retracted from the north and east and there are some indications that it continues to decline in certain regions.

Here is a COSEWIC management plan for the species, issued in 2013 and listing the following causes: “i) habitat loss and degradation from urban encroachment, cultivation of marginal native habitat and oil and gas development, ii) increased frequency of droughts associated with climate change, and iii) increase in predators associated with habitat fragmentation.”

Habitat matters when you are a bird that needs native grass to nest and Gulf Coast beaches to winter. A recent bird-tracking project initiated on the Gulf Coast of Texas  has made it very clear just how much the long-billed curlew depends on our efforts to hold on to the last pieces of its habitat north and south.

The website (thanks to photographer friend Val Mann for the tip!)tracks the movements of eight long-billed curlews that were given geo-locators, Argos Satellite Transmitters, last October as they arrived for winter in the Corpus Christi region of Texas. It appears that most of them spent much of the winter on a state park called Mustang Island, one of the few pieces of the Texas barrier islands that is not shellacked over with housing and resorts.

With the maps on the website, which are regularly updated with new satellite data from the birds’ geolocators, you can see that three of the curlews have made it to the Canadian Plains already. As of this week, one is north of Medicine Hat, Alberta, one is west of North Battleford, and and a third one is on the river breaks along the South Saskatchewan River north of Swift Current.

If you look at the movement of these three birds in recent days you will see that all three are using native grassland, though the two Saskatchewan curlews are travelling back and forth between cropland and native grassland.  In my experience at this time of year long-billed curlews are sometimes seen foraging in irrigated haylands, but they almost always make their nests in native grasslands nearby.

Here are a couple of maps showing the recent movements of the one north of Swift Current, back and forth between native grassland and cultivated land, but it always seems to be returning to one area in the native grass (circled in red in the second map).
It is a flight of seventeen hundred miles to get from the Texas coast to these northern plains. Hundreds of curlews give everything they have to make that journey twice a year. The least we can do is make sure that the habitat is still here and in good shape when they arrive.


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