Tuesday, October 02, 2007

Silent Autumn?

I've noticed dramatic shortages of some bird species this autumn. Specifically, at my place these ordinarily common species were way down in September 2007 in comparison to past years (based on birds seen or heard/hr of ordinary birding):

Green Heron (-100%; i.e. entirely absent)
Mourning Dove (-85%)
Yellow-billed Cuckoo (-100%)
Red-headed Woodpecker (-100%)
Red-eyed Vireo (-90%)
Tennessee Warbler (-85%)
Nashville Warbler (-100%)
Magnolia Warbler (-70%)
Bay-breasted Warbler (-80%)
Black-and-white Warbler (-85%)
American Redstart (-80%)
Scarlet Tanager (-90%)

Also, Eastern Meadowlarks are virtually absent from the entire county now. They are not normally regular at my farm, but they are usually numerous at several spots in the area. In recent weeks I have not seen a single one.

Are other people seeing similar trends elsewhere? Is this a local, statewide, or regional phenomenon? One could blame it on the boring weather not leading to migrant pileups, but that is pretty normal for September here and would have affected most previous years too (this is my 6th autumn here). It has gotten too late in the season to continue hoping that the big waves are just delayed and will show up eventually. It could be that the drought and freeze have left our local habitats so scarce on food that the migrants that do stop here leave the next night rather than sticking around; this would lower apparent abundances even if the total number passing through were the same. Or... worst case, it could indicate some massive nesting failures of woodland species to our north. For the most part, my tallies of local woodland and oldfield nesters are similar to previous years, in spite of the extreme weather. What are other people seeing?

The few species that were dramatically higher this September than previous years:

Ruby-throated Hummingbird (+375%) -- neighbors put up multiple feeders!
Swainson's Thrush (+300%) -- bucking the trend
House Finch (+infinity%, i.e. not recorded in previous Septembers) -- ditto on the feeders


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