Ecology of mallard ducklings on Lower Klamath National Wildlife Refuge, California Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/bc386p43g

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  • The ecology of female mallards (Anas platyrhynchos) and their broods was studied during 1988-90 on Lower Klamath National Wildlife Refuge, California. Survival of 127 radio-marked ducklings from 64 broods was 0.18 to 10 days of life, and 0.37 and 0.34 to fledging for 1988, 1989, and 1990, respectively. For the 3 years of the study, 49.2% of hens lost their entire brood; 81.2, 36.8, and 37.5% in 1988, 1989, and 1990, respectively. Ninety-three percent of mortality occurred on or before 10 days of life. No significant differences were detected in the proportion of radio-marked ducklings lost from early hatched or late hatched nests. A variety of predators consumed radio-marked ducklings; however, 49% of the cases of mortality were a result of an unknown predator. During 1989 and 1990, 3 radio-marked ducklings from 16 hens which appeared to lose their entire brood were fledged by other brood hens, and of 29 radio-marked ducklings that reached 44 days of life, 6 (20.7%) had joined other broods. Movements, home range, and habitat use were determined for 27 radio-marked broods. Relocation movements (>1000 m in 24 hrs) occurred in 12 of the 27 broods, primarily in the first week and after the fourth week of life. In 1989, significantly fewer radio-marked ducklings from broods hatching in permanent marshes survived to fledge compared to those originating in seasonal wetlands. Mean size of home ranges was 1.27 ± 0.47 km² and 0.62 ± 0.21 km² in 1989 and 1990, respectively. Most habitat selection by brood rearing hens occurred at the second order, (selection of home range area). Hens selected seasonally flooded wetlands with a cover component and avoided open or permanently flooded habitats. Estimated recruitment (females fledged/adult female in the spring population), proportional change in population size, and number of fledged young varied markedly during the 3 years of the study. Estimated recruitment was 0.31, 1.26, and 0.83 for 1988, 1989, and 1990, respectively. The estimated proportional change in population size ranged from 0.73 in 1988 to 1.29 and 1.04 during 1989 and 1990, respectively. Number of fledged young ranged from 915 in 1988 to 6,102 in 1989. Movements, habitat use, and survival of postbreeding radio-marked mallard hens were also determined. From mid-April to early August, 5,279 exposure days without the loss of a radio-marked hen were tallied. Of the 4 hens which emigrated from the study area, all were unsuccessful in rearing a brood. Unsuccessful hens moved to surveyed areas north of the study area significantly sooner than successful hens. Canals were the primary habitat utilized by postbreeding hens in 1988 while mixed seasonal and emergent permanent marsh were the most frequently used habitats in 1989 and 1990. Open seasonal and mixed seasonal marshes were the most frequently utilized habitats by incubating hens. Radio-marked hens moved a mean distance of 1,350 m from the nest to suspected feeding areas.
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