Wyniki wyszukiwania

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The breeding performance of the Common Buzzard Buteo buteo and Goshawk Accipiter gentilis in Central Poland

100%

Goszczynski J.

Acta Ornithologica

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2001

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tom 36

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nr 2

Both the Buzzard and the Goshawk nested mainly in pines. The mean clutch size in the former was 2.8, in the latter 3.6 eggs per breeding pair. There were statistically significant differences in clutch sizes in the Buzzard in particular breeding seasons. The mean number of hatchlings was 2.3 in the Buzzard and 2.6 in the Goshawk. Brood losses were similar in both raptors —19% in the Goshawk and 24% in the Buzzard. The breeding success (the ratio of the number of fledglings to the clutch size) in the Buzzard was highest in clutches of 3 and 4 eggsy whereas in the Goshawk a similar level of success was achieved with smaller clutches (2 or 3 eggs). Only in the case of the Buzzard there were significant differences in clutch sizes and numbers of fledglings in the various years. In this species the mean number of fledglings was positively correlated with the rodent availability index in a given year. There was no such relationship between the abundance of prey items found in Goshawk nests and the number of fledglings. The correlation between the number of newly-fledged Buzzards and Goshawks in a given year could have been due to diet overlap between the two species.

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Parental provisioning in response to natural variation of brood size in the Black-billed Magpie (Pica pica): video analysis of behaviors in the nests

80%

Lee S., Choi J., Jablonski P. G., Choe J. C.

Polish Journal of Ecology

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2010

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tom 58

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nr 3

Natural selection will favor parents who adjust their effort in relation to the fitness costs and benefits from the current brood. In this study, we investigated how magpie parents adjust provisioning effort based on the number of nestlings in the brood, by analyzing video recordings of begging and feeding behaviors of birds. The number of visits per hour increased with brood size, but the number of feeding events per visit did not. Because of the latter, parental provisioning that a nestling is receiving on average decreased in larger broods. This may be viewed either as an evidence for the limitation of parental provisioning in larger broods, or as an evidence of parental strategy optimizing the brood-size-specific provisioning effort for the current reproductive event as a tradeoff between current and future reproduction. With other aspects of parental provisioning behavior, we did not find clear indication that parent confronts upper limitation in provisioning large broods. Pervisit number of feeding and nestlings’ body condition around the time of fledging did not depend on brood size, which implies that parental effort is not at its limit in larger broods. Based on the results, we suggest that the provisioning effort of black-billed magpie parents is better explained by the life-history trade-off model for provisioning.

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Impact of local air temperatures on the brood size in starling [Sturnus vulgaris L.]

80%

Dolenec Z.

Polish Journal of Ecology

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2009

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tom 57

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nr 4

817-820

Many papers over recent years have demonstrated long-term temporal trends in biological parameters that can only be explained by global warming. I examined the long-term trends in the brood size of Starling (Sturnus vulgaris) in Mokrice area (north-western Croatia). I collected data from 1977 to 2007. To investigate the effect of spring temperatures on the brood size, local air temperature was used. The significant correlation (P <0.01) between mean brood size and the year (y = – 31.403 + 0.018x) indicates that brood size (mean number of nestlings per nest) increased by 0.018 nestling per year, or 0.54 nestling over the period of the study. Correlation between brood size (mean number of nestlings per nest) and mean spring temperature was also significant (P <0.05) and regression equation (y = 4.162 + 0.07x) indicates that brood size increased by 0.07 nestling per 1ºC. The correlation between mean spring air temperature and research year was significant (P <0.01). This data show that the mean May temperature has been increasing in the study area. We can conclude that Starlings in north-western Croatia are increasing their brood size and that the most likely cause is a long-term increase in spring temperatures.

Ograniczanie wyników

2 Polish Journal of Ecology

1 Acta Ornithologica

1 Choe J. C.

1 Choi J.

1 Dolenec Z.

1 Goszczynski J.

1 Jablonski P. G.

1 Lee S.

1 2010

1 2009

1 2001

The breeding performance of the Common Buzzard Buteo buteo and Goshawk Accipiter gentilis in Central Poland

Parental provisioning in response to natural variation of brood size in the Black-billed Magpie (Pica pica): video analysis of behaviors in the nests

Impact of local air temperatures on the brood size in starling [Sturnus vulgaris L.]