An assessment of DDT and other chlorinated compounds and the reproductive success of American robins (Turdus migratonrius) breeding in fruit orchards.
Although DDT was banned in the 1970s, American robins (Turdus migratorius) breeding in fruit orchards of the Okanagan Valley, British Columbia, continue to be contaminated with DDT and its metabolites. The objectives of our study were (1) to assess organochlorine (OC) contamination in robins breeding in Okanagan orchards (1993-1995, 1997-1998) and (2) to determine if exposure affected reproductive success when compared to robins from non-orchard habitat (lower mainland, British Columbia). Robins in orchards had total DDT egg residues of 48.64 mg/kg (geometric mean; n = 92) while those in non-orchard habitat had 1.10 mg/kg (geometric mean; n = 26), wet weight. The probability of nest survival during the incubation period was 96.7% (confidence interval: 95.7-97.5%; n = 165) in orchard habitat and 96.7% (confidence interval: 94.6-98.1%; n = 28) in non-orchard habitat. During the nestling period the probability of nest survival was 98.2% (confidence interval: 97.2-98.9%; n = 123) in orchard habitat and 96.2% (confidence interval: 92.8-98.0%; n = 34) in non-orchard habitat. Clutch (p < 0.0001) and brood size (p = 0.0133) were larger in orchards (n = 150 and n = 93, respectively) compared to non-orchard nests (n = 42 and n = 23, respectively) with no difference in fledge rate. DDE (r2 = 0.11, p = 0.0030, n = 68) and dieldrin (r2 = 0.29, p < 0.0001, n = 68) were negatively correlated with fledge rate in robin eggs collected from orchard habitat, however, low r2 values signify minimal biological significance. Although American robins nesting in Okanagan orchards are exposed to high OC levels, reproductive success does not appear to be negatively impacted.
Agroecology Group, Faculty of Agricultural Sciences, University of British Columbia, 2357 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4.
Harpreet
H
Gill
Laurie K
LK
Wilson
Kimberly M
KM
Cheng
John E
JE
Elliott
D000383:Agriculture; D000818:Animals; D001955:British Columbia; D003634:DDT / Q000009:adverse effects*; D004781:Environmental Exposure; D005260:Female; D005638:Fruit; D007306:Insecticides / Q000009:adverse effects*; D008297:Male; D011157:Population Dynamics; D012098:Reproduction / Q000187:drug effects*; D020308:Songbirds; D013534:Survival
D007306:Insecticides; D003634:DDT