In a new paper published in The Condor, entitled WINTER SURVEY DATA REVEAL RANGEWIDE DECLINE IN EVENING GROSBEAK POPULATIONS, coauthors David N. Bonter and Michael G. Harvey detail the ongoing decline of this species. For many decades a common species in winter in the northern third of Wisconsin, this species has declined considerably in numbers here and across the northern United States and southern Canada. Explanations range from diseases, habitat alteration, fewer infestations of spruce budworm in the boreal forest region, coupled with the possible effects of climate change. The folks at Cornell who work on this have a webpage on this, too, and it points toward the same conclusions; see it here. Very worrisome; this is a much-beloved bird species. There is evidence to suggest that the larger populations we've noted here in the past 50-70 years may have only been a recent phenomenon, and that they were formerly less common in the Great Lakes states and New England anyway. Winter in Wisconsin is not the same without these colorful, big-billed sunflower seed gluttons. Of course things are always changing with bird populations, and anthropogenic effects often seem to greatly accelerate the changes that might occur in any case.