Results 111 to 120 of about 570 (161)
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Egg-Eating by Female Brown-Headed Cowbirds
The Condor, 1992We estimated the proportions ofeggs and nestlings, removed from hosts' nests, that were eaten by female Brown-headed Cowbirds (Molothrus ater) from (1) a compilation of published and unpublished observations (n = 36) of egg or nestling removal and egg- eating by female cowbirds and (2) the proportion of removed eggs that were found uneaten below ...
Scott, David M. +2 more
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Female spacing patterns in brown-headed cowbirds
Canadian Journal of Zoology, 1985Breeding female cowbirds at the Queen's University Biological Station are often aggressive when encountering other females within their ranges, but they do not defend exclusive territories. The likelihood of aggression appears to be a function of two factors. First, females are more aggressive near the centres of their ranges than around its periphery,
Kevin L. Teather, Raleigh J. Robertson
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Evolution of Promiscuity in the Brown-Headed Cowbird
The Condor, 1980--A study of the social behavior of Brown-headed Cowbirds (Molothrus ater) in 1974 and 1975 suggests that in prairie communities the predominant mating behavior is promiscuous. Individually marked cowbirds of both sexes were observed copulating with more than one individual, suggesting that long-term pair bonds were non-existent.
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Estrogen Synthesis and Secretion in the Brown-Headed Cowbird (Molothrus ater)
General and Comparative Endocrinology, 1997Estrogens exert profound effects on vertebrate physiology and behavior. In most vertebrates, including birds, estrogens derived from ovarian tissue circulate at high levels during discrete periods of reproductive activity, and estrogen levels in males are low. In some songbirds (Passeriformes) plasma estrogens are high in both males and females. In the
C J, Saldanha, B A, Schlinger
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Lateralization and motor stereotype of song production in the brown‐headed cowbird
Journal of Neurobiology, 1994AbstractSong production in adult brown‐headed cowbirds(Molothrus ater ater) is lateralized, with a slight right syringeal dominance. The left size of the syrinx produces low‐frequency (200–2000 Hz) notes within the introductory note clusters, while the right side produces the higher‐frequency (1500–6000 Hz) introductory notes, the interphrase unit (10 ...
S E, Allan, R A, Suthers
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Gray Jays Accept Brown-headed Cowbird Eggs
The Wilson Journal of Ornithology, 2009Abstract Results of simulated brood parasitism on five Gray Jay (Perisoreus canadensis) nests suggest acceptance of model Brown-headed Cowbird (Molothrus ater) eggs. This finding is contrary to results of experimental parasitism on four other species of jays, also with little or no recent history of parasitism, which eject cowbird eggs. Given that Gray
Spencer G. Sealy +2 more
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Reproductive Costs of Commuting Flights in Brown-Headed Cowbirds
The Journal of Wildlife Management, 2003Brood parasitism by brown-headed cowbirds (Molothrus ater, hereafter cowbird) has attracted much attention from conservation biologists as an edge effect over small spatial scales, reducing nesting success of songbirds near habitat boundaries. The mechanisms underlying this landscape-scale edge effect have not been studied, but this phenomenon has been
David R. Curson, Nancy E. Mathews
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The Laying Cycle of Brown-Headed Cowbirds: Passerine Chickens?
The Auk, 1983Abstract We collected 270 female Brown-headed Cowbirds (Molothrus ater) in southern Ontario in 1976 to determine ovarian and oviducal growth during the breeding season and 188 female cowbirds in 1977 to estimate clutch size and the interval between clutches.
Scott, D. M., Ankney, C. Davison
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Behavioral Ecology of Fledgling Brown-Headed Cowbirds and Their Hosts
The Condor, 1983Twenty-two fledgling Brown-headed Cowbirds (Molothrus ater) raised by nine host species were monitored between leaving the nest and independence. The objectives were (1) to record as much as possible about the fledgling period, especially those features that enable cowbirds to become independent, (2) to determine if fledglings behaved differently with ...
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Song Sharing in the Brown‐headed cowbird (Molothrus ater)
Zeitschrift für Tierpsychologie, 1985Abstract and SummarySongs were recorded from two separate populations of brown‐headed cowbirds (Molothrus ater). High levels of song sharing were found in each and, in one population, paired males shared more song types than did the remainder of the population.
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