The Breeding Season of a Parasitic Bird, the Brown-Headed Cowbird, in Central California

Payne, Robert B.

doi:10.2307/1366537

Cited by 59 publications

(26 citation statements)

References 34 publications

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“…In this study and others (e.g., Lowther 1977;Ankney and Johnson 1985), cowbird egg mass generally increased over the laying season, indicating that the resources needed for a high rate of egg production may initially be more dicult to acquire (see Perrins 1970;Payne 1973). This ®nding indicates that the advantages of laying a larger egg early in the season may not be as great as laying more eggs.…”

Section: Possible Factors Limiting Cowbird Reproductionsupporting

confidence: 57%

Temporal patterns of host availability, brown-headed cowbird brood parasitism, and parasite egg mass

Strausberger

1998

Oecologia

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I studied relationships between temporal patterns of host availability, brood parasitism, and egg mass for the parasitic brown-headed cowbird (Molothrus ater). At a study site consisting largely of edge habitat in north-eastern Illinois, I found 834 bird nests from 27 species. A total of 407 cowbird eggs and nestlings were found in these nests over three laying seasons. Nearly all (n= 379; 93%) were found in the nests of seven host species. For these species and all taken together, weekly nest availability generally decreased whereas parasitism frequency generally increased throughout the cowbird laying season, but the proportions of nests parasitized and the mean number of cowbird eggs in them did not. Additionally, no correlation was found between the proportions of nests parasitized and nest availability. Cowbird egg mass generally increased throughout the laying season, indicating that foraging conditions improved and that, early in the laying season, egg mass and quality may be less important than quantity. Consistently high weekly levels of parasitism indicate that cowbird reproduction was less limited by resources needed for egg production and more by the availability of suitable host nests. Fluctuating weekly host availabilities suggest that previously established, constant rates of cowbird egg laying would produce an excess of eggs during periods of low host availability. Further, the low frequency of parasitism (1%) of nests in stages too advanced for successful parasitism, and of abandoned nests, is consistent with the hypothesis that cowbirds' consistently high rate of egg production helps assure an egg is available when an appropriate nest is found. Frequently, nests were parasitized multiple times, raising the possibility that cowbirds were interfering with their own reproduction. A diverse host community increases the possibility that a decline of any one host species is unlikely to affect cowbird reproduction significantly.

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Section: Possible Factors Limiting Cowbird Reproductionsupporting

confidence: 57%

Temporal patterns of host availability, brown-headed cowbird brood parasitism, and parasite egg mass

Strausberger

1998

Oecologia

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Section: Methods Subjects and Housing Conditionsmentioning

confidence: 99%

“…However, all birds were breeding adults and thus brains were unlikely to be more plastic in females because of age. All birds were killed between May and June, a period that coincides with the breeding season in California cowbirds (Payne, 1973).We had three conditions: wild-caught birds, birds held captive in aviaries, and birds housed in isolation chambers (females only). Captive birds were six males (CM) and five females (CF) captured between late April and early July of 1999 and housed in a large outdoor aviary (1.2 × 2.7 × 6.0 m) in mixed-sex groups until killed between May 12 and June 30 of 2000, approximately 1 year after their capture.…”

mentioning

confidence: 99%

Sex differences in the effects of captivity on hippocampus size in brown-headed cowbirds (Molothrus ater obscurus).

Day

Guerra²,

Schlinger³

et al. 2008

Behavioral Neuroscience

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In brood parasitic cowbirds, hippocampus (Hp) size is correlated with environmental spatial memory demands. Searching for host nests is the presumed causal factor influencing cowbird Hp size, because Hp volumes vary across species, sexes, and seasons according to nest-searching participation. Brownheaded cowbirds have female-only nest searching and, at least in the eastern subspecies, a larger Hp in females than in males, suggesting that nest searching influences cowbird Hp size. We predicted that female brown-headed cowbirds housed in aviaries lacking host nests would have a smaller Hp than wild-caught females whereas males would be unaffected. We found that the Hp was smaller in captive females, but not males, compared to their wild-caught counterparts. This did not appear to be due to general effects of an impoverished environment on all brain regions. Our results imply that interruption of nest searching in cowbirds prevents seasonal increase in Hp size in females. Future studies should isolate which behavioral differences between wild and captive birds contributed to captivity-induced changes in Hp volume in females while not affecting males. Keywordscowbird; hippocampus; sex differences; brain plasticity; brood parasitism Variation in environmental spatial demands is related to variation in hippocampus (Hp) size among closely related species, between sexes, and across seasons in mammalian, avian, and reptilian species. For example, food-storing behaviors in birds (Clayton, 1995a;Hampton, Sherry, Shettleworth, Kurgel, & Ivy, 1995;Hampton & Shettleworth, 1996;Healy & Krebs, 1992;Krebs, Sherry, Healy, Perry, & Vaccarion, 1989;Sherry, Vaccarino, Buckenham, & Herz, 1989;Volman, Grubb, & Schuett, 1997) and rodents (Jacobs, 1992;Jacobs & Spencer, 1994), foraging-related rate of movement in lacertid lizards (Day, Crews, & Wilczynski, 1999), home-range size in voles (Gaulin, 1992;Jacobs, Gaulin, Sherry, & Hoffman, 1990 Sherry, Jacobs, & Gaulin, 1992), and breeding-habitat complexity in petrels (Abbott, Walsh, Storey, Stenhause, & Harley, 1999) are all associated with enlarged Hp size, presumably due to the demands of spatial memory. In addition, seasonal variation in food-storing demands is associated with seasonal changes in Hp volume (Smulders, Sasson, & DeVoogd, 1995) in black-capped chickadees and rodents (Jacobs, 1996). Males have a larger Hp than females in a vole species in which males have larger home ranges but not in vole species that do not have sex differences in home range (Gaulin, 1992). These results provide evidence that environmental or experiential seasonal changes can alter Hp volume and that natural and sexual selection on a variety of spatial-related skills has produced a larger Hp in some species or sexes than in others.Although correlations of Hp volume with ecological demands for spatial ability are numerous, the specific mechanisms that contribute to such adult variation in the volume of the Hp are not well understood. We do know that species-specific reactions to spatial experience...

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“…But usually the patterns are not as weIl defined because prime breeding and feeding habitat generally occur elose together due to the pervasiveness of human influence, especially agrieulture. Workers in the East and Midwest (Payne, 1965;Kennard, 1978;Raim, 1978;Dufty, 1982a) and in agricultural areas within California (Payne, 1973) have noted that daily breeding and feeding activities are separated spatially and temporally, but it is evident that the commuting is less extreme. The birds spend more time in the morning at feeding sites than do those at Mammoth because such sites are elose to breeding habitat.…”

Section: Field Studies Of Phenomena That Showmentioning

confidence: 99%

“…Payne sectioned ovaries and estimated that females lay 10-12 eggs per season in northern lower Michigan. Subsequently, Payne (1973) estimated that cowbirds in the Central Valley of California lay 30 eggs per season and attributed the difference between California and Michigan to birds in the former state having a longer laying season and laying more eggs per clutch. But the California estimate was also partly arrived at by a new technique.…”

mentioning

confidence: 99%

Social Dominance, Mating and Spacing Systems, Female Fecundity, and Vocal Dialects in Captive and Free-Ranging Brown-Headed Cowbirds

Rothstein

Yokel

Fleischer

1986

Current Ornithology

128

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The Breeding Season of a Parasitic Bird, the Brown-Headed Cowbird, in Central California

Cited by 59 publications

References 34 publications

Temporal patterns of host availability, brown-headed cowbird brood parasitism, and parasite egg mass

Temporal patterns of host availability, brown-headed cowbird brood parasitism, and parasite egg mass

Sex differences in the effects of captivity on hippocampus size in brown-headed cowbirds (Molothrus ater obscurus).

Social Dominance, Mating and Spacing Systems, Female Fecundity, and Vocal Dialects in Captive and Free-Ranging Brown-Headed Cowbirds

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