The Evaluation of Christmas Bird Counts as an Indicator of Population Trends and Habitat Selection in Blackbirds and Starlings

Abstract

Agelaius phoeniceus (red-winged blackbird), Quiscalus quiscula (common grackle), and Sturnus vulgaris (European starling) are three of the most abundant bird species found in North America, and along with Euphagus carolinus (rusty blackbird) and Euphagus cyanocephalus (Brewer’s blackbird), make up a significant proportion of the avian population. Population trends of these four blackbird species and European starlings (EUST)were analyzed from the Christmas Bird Count (CBC) data collected between 1988 and 2008. Population analyses were conducted using linear mixed-effect regressions from the Lmer package of Program R. This approach was effective in modeling the population trends of widespread species with large populations. However, it was not as effective in modeling species with smaller populations and distributions. Only RWBL had significant change in population during the study period, showing a positive increase in mean count number of approximately 2.4% each year. Habitat selection showed some parallels among species.