We used detections based on this criterion within 30 m for Yellow-rumped Warbler (Dendroica coronata); 60 m for Savannah Sparrow (Passerculus sandwichensis); 70 m for Gray Jay (Perisoreus canadensis), Wilson's Warbler (Wilsonia pusilla), and American Tree Sparrow (Spizella arborea); 125 m for American Pipit (Anthus rubescens), Horned Lark (Eremophila alpestris), and Pine Grosbeak (Pinicola enucleator); and 150 m for the other 20 species.
White-winged Crossbills (Loxia leucoptera; 443,000 individuals) were the most abundant resident passerine, followed by Boreal Chickadee (Poecile hudsonica; 307,000) and Gray Jay (229,000).
Gray Jays belong to the Old World clade of corvids (Ericson et al.
The results suggest that Gray Jays accept model cowbird eggs, although a larger sample might reveal a low level of ejection.
2007); hence, acceptance by Gray Jays is exceptional.
This is not to suggest that rejection has been lost in the absence of parasitism, rather it may be more likely that Gray Jays and their congeners were not parasitized in their evolutionary histories, given their preferred breeding habitat, early onset of nesting seasons, and that rejection evolved later in other species in the Corvidae.
DS initiated a study of the population biology of the Gray Jay >30 years ago (Rutter 1969, Strickland and Ouellet 1993) in Algonquin Park, Ontario, adjacent to Provincial Highway 60 where it crosses the southwest corner of the Park (45[degrees] 33' N, 78[degrees] 33' W).
Gray Jay eggs are larger than Brown-headed Cowbird eggs and have a different base color and pattern (Lowther 1993, Strickland and Ouellet 1993).