Care of Nestlings by Wild Female Starlings Exposed to an Organophosphate Pesticide

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Abstract
The effect of exposure to an organophosphate pesticide (OP), dicrotophos [insecticide] on care of nestlings by wild female starlings (S. vulgaris) was determined. Pairs (12) of active nests were selected on the basis of synchrony in the reproductive cycle. When nestlings were 10 days old (day 10), adult males were captured and killed and brood size was adjusted to 4. The frequency and temporal distribution of sorties made by each pair of females to feed their young were recorded for 2 h at 1800 h on day 11 and 0600 h on day 12. One female from each pair was given a single oral dose of dicrotophos (2.5 mg/kg body wt) dissolved in corn oil; the 2nd female received an equivalent exposure of pure corn oil. Birds were released and their nestlings weighed. Parental care was again monitored between 1800-2000 h on day 12 and 0600-0800 h on day 13. Females were captured, and they with their young were weighed and killed. Changes in parental care in OP-dosed and control females were compared in paired t-tests. The OP-dosed females made significantly (P L 0.05) fewer sorties to feed their young and remained away from their boxes for longer periods of time than controls. Nestlings of OP-treated females lost significantly more weight (.hivin.X [mean] = 9.3%) than did nestlings of controls (.hivin.X = 3.2%). Brain ChE [cholinesterase] activity in OP-treated females was inhibited an average of 50.7% compared with controls. Weight changes in OP-dosed (.hivin.X = -8.9%) and control females (.hivin.X -8.3%) were similar. Parental care may be significantly reduced in songbirds receiving severe but sublethal exposure to OP. The potential for a reduction or modification in parental care to alter reproductive success in passerines was discussed. Techniques or modifications utilized may be useful in collecting additional data needed to adequately assess the impact of OP on songbird reproduction.