Backyard Bird Numbers Down?

I'm hearing reports from friends that their backyard birdfeeders are not needing as frequent refills as in past years, meaning there are fewer birds around. Though we don't have a birdfeeder, I noticed a flurry of bird activity in the backyard in early to mid-December, with mixed groups of birds visiting and then moving on, but have seen almost none since then.

This from Bill Sachs of Princeton:

In winters past, we have had to replenish the seed in our backyard birdfeeder at least twice a week.  This winter, the birds seem  noticeable by their absence and the interval between needed refills has exceeded two weeks!  Oh, we have birds visiting the feeder from time-to-time, especially mourning doves and blue jays, but visits by chickadees, titmice, nuthatches and wood peckers seem much reduced.  I am curious because there was a review article in a recent edition of Science magazine on “Globalization, Land Use, and the Invasion of West Nile Virus” (A. M. Kilpatrick, Science, 334: 323-327) in which the author writes,

“The impacts of WNV on wildlife have been yet more severe than those on humans.  Millions of birds have died from WNV infection, and regional-scale population declines of >50% have been observed for several species (11).  The range of taxa that have suffered declines is surprisingly large and includes corvids, chickadees and titmice, wrens, and thrushes (Fig. 1) and probably others.  Some populations have recovered after initial declines, whereas others have not.”

And this from an avid birder in town:

We too have had fewer birds at our feeder. Don't know why. Maybe mild weather, more berries, more insects? We've had a lot of Red-Tailed Hawks in the neighborhood, too. Declines of migratory birds, e.g., thrushes, have been occurring over a few decades, and that's due to multiple factors, including loss of winter habitat in the tropics. Among the year-round residents, or short distance migrants, disease could be a factor. Blue Jays were victims a while back, but seem to have recovered. House Finches, on the other hand, were decimated by disease a few years ago and have not come back.


Note: Ran into Henry Horn, professor emeritus at the PU Dept. of Ecology and Evolutionary Biology, who agrees that birds are very scarce. Closer to usual numbers are bluejays, crows and Carolina wrens. 


Note #2: Data from the Princeton Christmas Bird Count, and also from the national Cornell Backyard Feeder Watch, will be available soon. I'll post that when it comes in.