January 21, 2011
One of the most common winter visitors to bird feeders across North America is becoming less common. The Evening Grosbeak is an irruptive migrant, occasionally moving out of its boreal and montane breeding ares to winter at lower latitudes and elevations. These yearly fluctuations have been documented by participants of Project FeederWatch, allowing researchers at the Cornell Lab of Ornithology to track changes in the abundance and distribution of the species. According to a recent study, reports of Evening Grosbeaks at FeederWatch sites declined by fifty percent between 1988 and 2006. At sites where Evening grosbeaks continue to be reported, average flock size had decreased by twenty-seven percent.
Unfortunately, the factors behind these declines are still not clear. While Evening Grosbeaks are gregarious during the winter, foraging together in large flocks, they are relatively solitary during the breeding season. There are currently significant gaps in basic life-history information for this species. Developing a plan to slow the decline of the Evening grosbeak will require better information on their breeding biology and reproductive success.
More information about the Evening Grosbeak can be found on All About Birds.
Source: Bonter D. N. and M. G. Harvey. 2008. Winter survey data reveal rangewide decline in Evening Grosbeak populations. Condor 110:376-381.