Rebounding Peregrine Falcons Force Shorebirds to Get Fit

peregrine falcon photo

Image credit: mikebaird/Flickr

Due mostly to the widespread use of DDT, peregrine falcon populations in North America reached a dangerously low level in the 1970s, when the species was listed as endangered. Thanks to a ban on the toxic pesticide, captive breeding programs, and other conservation efforts, populations in the United States and Canada have largely rebounded.

This success, new research has found, is forcing some shorebirds to change their behavior. Instead of fattening up for a sedentary winter, Pacific dunlins are now staying lean and active to better avoid the falcons.Ronald Ydenberg, an ecologist at Simon Fraser University, explained:

In the past, dunlins stored up fat reserves in the autumn months so that they could survive the harsh Canadian winters when food is short. What we're seeing now, however, with the increase in numbers of peregrine falcons, is that the dunlins have to consider the energy trade-off between preparing for starvation and being able to escape quickly.

The research, published in BMC Ecology, found that the average weight of dublins has decreased two to four grams over the past 40 years. In addition, energy-intensive behaviors, like over-ocean flocking, have increased in the winter. Though these changes make starvation a real possibility, they help the birds escape predation by the falcons.

Dick Dekker, a member of the research team, commented that "over-ocean flocking is energetically expensive...but the risk from predators is now greater than the threat of starvation." The team concluded that their research demonstrates the complex ways in which Pacific dunlins respond to danger but it is also an excellent example of the spidering effects of ecological change.

Read more about peregrine falcons:
DDT Redux: PBDEs In Peregrine Falcons Close To Levels Damaging Developing Lab Rats & Mice
Watch the Falcons Living in Sagrada Familia Cathedral via Web Cam
Superior Islands: Ontario's Largest Conservation Project Will Protect 4,700 acres

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