Sperm transfer in the Adelie Penguin
Article Abstract:
Cloacal contact is an unreliable indicator of sperm transfer in Adelie Penguins (Pygoscelis adeliae). The failure of transfer is due to improper positioning of the ejaculate on the female's cloaca or the male's failure to ejaculate. A small proportion of the failure is due to the absence of sperm in the ejaculate, since 95.7% of inseminated ejaculates contain sperm. Sperm transfers occur in 70.1% of behaviorally successful copulations in wild birds, which is similar to that observed in captive birds. Observation of an ejaculate in the female's cloaca should provide a better indication of successful transfer of sperm.
Publication Name: The Condor
Subject: Biological sciences
ISSN: 0010-5422
Year: 1996
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Unsuitability of the House Finch as a host of the Brown-headed Cowbird
Article Abstract:
The House Finch (Carpodacus mexicanus) is an inappropriate host for Brown-headed Cowbirds (Molothrus ater). The nestling diet appears to be a major factor that influences the cowbird's choice of host. A study conducted in Canada between 1983-1985 and 1990-1993 reveals that the growth rate of cowbirds raised in house finch nests is extremely slow, though the hatching rate is 84.8%. The cowbird nestlings require twice as much time to grow to the same level as in other hosts and their body mass is 22% below normal. The average survival time is 3.2 days.
Publication Name: The Condor
Subject: Biological sciences
ISSN: 0010-5422
Year: 1996
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Territorial position in sharp-tailed grouse leks: the probability of fertilization
Article Abstract:
The relationship of the territorial positionof males in sharp-tailed grouse leks to the probability of fertilization was investigated. Males who had central positions were found to have larger testis volume than peripheral males. Larger testis volumes imply higher sperm production. A positive correlation between testis volume and body mass was alsoobserved. Large body mass may therefore be an indicator to females that the probability of fertilization after mating with a particular male is high.
Publication Name: The Condor
Subject: Biological sciences
ISSN: 0010-5422
Year: 1992
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