Article Abstract:
The Redhead parasites outnumber the breeding canvasback hosts and heavily parasitized Canvasback nests on a Delta Marsh as a result of brood parasitism. High rates of parasitism are due to a delayed host-embryo development, longer incubation periods and extended brooding behavior at nests containing unhatched eggs. Laying female parasites displaces incubating hosts, which causes accidental displacement of the eggs from the nest. The host defensive behavior indicates that brood parasitism presents fitness costs by affecting the critical processes of synchronous hatching.
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Article Abstract:
Intraspecific variation in nutrient reserves has little significance in determining the future reproductive success of adult Canvasbacks and Redheads. The nutrient-limitation hypothesis tested on Redheads and Canvasbacks shows that while body mass does not have any impact on the subsequent nesting successes of Redheads and adult Canvasbacks, it affects the reproductive success of yearling Canvasbacks. It is observed that brood survival and adult survival is not dependent on female body mass for either species.
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Article Abstract:
Conspecific nest parasitism is anlyzed. The observations made in the nest of a Sora, Porzana carolina suggests CNP's occurrence as well as a very fine egg discrimination. In precocial species such as this one CNP is very regular phenomenon. The observations mentioned are in line with the studies of other rallids. The egg rejection behavior of the Sora has been analyzed after observations made at Manitoba, an area near Minnedosa, characterized by high densities of small wetlands and breeding waterfowl.
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