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. / Graduation date: 1992
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36533 |
| Date | 09 December 1991 |
| Creators | Mauser, David M. |
| Contributors | Jarvis, Robert L. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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