. The Canadian field-naturalist. 1990 Court et al.: Toxicological Assessment of Peregrine Falcons 259 Table 1. Eggshell thickness of Peregrine Falcons nesting at Rankin Inlet Sample Mean (± SD) eggshell n thickness (mm) All eggs 78 + Eggs representing clutches 62 + Eggs recovered as fragments Eggs recovered intact 32 30 + + Difference {py Eggs from successful nests 40 + Eggs from unsuccessful nests 9 + Addled eggs 1981 to 1985 14 + "Storm-killed" eggs 1986 16 + 'Based on
. The Canadian field-naturalist. 1990 Court et al.: Toxicological Assessment of Peregrine Falcons 259 Table 1. Eggshell thickness of Peregrine Falcons nesting at Rankin Inlet Sample Mean (± SD) eggshell n thickness (mm) All eggs 78 + Eggs representing clutches 62 + Eggs recovered as fragments Eggs recovered intact 32 30 + + Difference {py Eggs from successful nests 40 + Eggs from unsuccessful nests 9 + Addled eggs 1981 to 1985 14 + "Storm-killed" eggs 1986 16 + 'Based on Student's t-tests. Only 12 (19%) of 62 eggs representing clutches showed less than 10% thinning. In our sample, shell thickness did not vary significantly among years (ANOVA F4 57 = P= ). Mean shell thickness for eggs recovered as fragments was Table 2. Levels of organochlorine residues in Peregrine Falcon eggs from 36 different nesting attempts' at Rankin Inlet. Compound Range Geometric Mean DDE PCB Dieldrin Heptachlor Epoxide Oxychlordane DDT DDD Hexachlorobenzene 'Includes residues from 25 single eggs and 11 clutch means. not significantly different to that for whole eggs (Table 1). Shells from addled eggs collected between 1981 and 1985 were significantly thinner that those from the "storm killed" sample of 1986 (Table 1). Nine of 14 nesting failures in 91 nesting attempts (1981 to 1985) involved breakage of one or more eggs in a clutch (Figure 2). Shells from failed nests averaged less than the pre-DDT average, while those from successful nests averaged less than the pre-DDT average; the difference was significant (Table 1). We found no significant correlation between shell thickness and number of young fledged (n = 62 r = P - ).. P V-. Please note that these images are extracted from scanned page images that may
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