. The Canadian field-naturalist. 478 The Canadian Field-Naturalist Vol. 113. â 1 Residuals % Doves Figure 5. Least-squares linear regression of nest success rate on percentage of doves at 11 NNYNE eyries where > two prey samples were collected and peregrines nested for > four years in Northern New York and New England, 1989-1996. Residual plot removes confounding effects of average prey biomass (total prey biomass/number of samples) showing a strong significant (r^ = ; P 2/3 of prey biomass in the other ecoregions (Figure 4). Historically, doves were an important prey
. The Canadian field-naturalist. 478 The Canadian Field-Naturalist Vol. 113. â 1 Residuals % Doves Figure 5. Least-squares linear regression of nest success rate on percentage of doves at 11 NNYNE eyries where > two prey samples were collected and peregrines nested for > four years in Northern New York and New England, 1989-1996. Residual plot removes confounding effects of average prey biomass (total prey biomass/number of samples) showing a strong significant (r^ = ; P 2/3 of prey biomass in the other ecoregions (Figure 4). Historically, doves were an important prey item for northeastern peregrines (Hickey and Anderson 1969) and, as granivores, they generally accumulate much lower contaminant levels than smaller omnivo- rous passerines (Enderson et al. 1982), while pre- sumably providing more biomass per unit catch effort. Because we did not measure contaminant lev- els in peregrines or their prey, it is unclear whether differences in reproductive performance result from a largely passerine diet with higher contaminant con- centrations. Nevertheless, doves clearly play a prominent role in the reproductive performance of NNYNE peregrines. Chronic nest failure at some White Mountain eyries (Audubon Society of New Hampshire, unpub- lished data; Maine Department of Inland Fisheries and Wildlife, unpublished data), high rates of eggshell thinning (Gikoy and Barclay 1988; USFWS unpublished data), prolonged incubation periods (Martin and North 1993) and high PCB and organochlorine levels in unhatched eggs (Bums et al. 1994; Jarman et al. 1993) all suggest that peregrines in this area may be experiencing ongoing exposure to high levels of contamination. Because doves tend to thrive in agricultural and non-forested (DeGraaf and Rudis 1987) such as the Champlain and Piedmont ecoregions, geographic variability in pere- grine reproductive performance may ultimately be related to habitat differences. Acknowledgments Earlier drafts of the manuscript w
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