Article Abstract:
Predation and exposure to precipitation and cold temperature were found to be the major causes of mortality among canvasbacks. In a study of these ducks at the Agassiz National Wildlife Refuge in northwestern Minnesota from 1987 to 1990, duckling survival was estimated by using the Kaplan-Meier nonparametric estimator and the Weibull parametric model. Mortality was found to strike the ducklings within 10 days after hatching. Males were also found to have higher survival than females, which may later contribute to a decrease in canvasbacks' reproductive potential and a male-biased sex ratio.
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Article Abstract:
A reliable technique for radiomarking ducks was tested on captive mallards. Intra-abdominal radiotransmitters were surgically implanted in the abdominal cavity with its external whip antennas exiting through the abdominal wall and skin. Birds which have been implanted with transmitters were found to have developed mild to moderate localized air sac reactions, involving adhesions of the right anterior abdominal air sac to the liver. The mallards did not exhibit any change in their behavior or activity as caused by a histological reaction to the transmitter implant.
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Article Abstract:
Telemetry equipments were assessed for their potential effects on the development of mallard ducklings. The thermal responses of 1-day old mallard ducklings fitted with external sutured backpacks or subcutaneously implanted transmitters were compared with untreated ducklings. Ducklings with external backpacks showed increased surface temperatures but showed little difference compared with ducklings with implants and untreated ducklings in respirometry studies and wind cooling studies.
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