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

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Lee S. , Jabłoński P. , Choe J. , Choi J.

Polish Journal of Ecology

2010

tom Vol. 58, nr 3

553-562

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.

Urban and natural components of Korean magpie (Pica pica sericea) territories and their effects on prey density

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Kim S. , Srygley R. , Lee J. , Lee S. , Choe J.

Polish Journal of Ecology

2012

tom Vol. 60, nr 2

407-417

Urban landscapes have a negative impact on bird species diversity, yet particular species thrive in urban communities. Like many other corvids, the Korean magpie is a successful colonizer of urban environments. On the semiurban campus of Seoul National University in Korea, we investigated whether magpies adjust territory size with building area and secondarily, whether they use vegetation and artificial components of their territory as indicators of prey density. We measured territorial areas and divided these into vegetation and artificial areas, distinguishing building area as a separate feature. We sampled prey density on each territory during the nestling stage. Territory size increased with the square root of building area (SRBA). As the length of building perimeter also increases with SRBA, we conclude that territory size was proportional to building perimeter. Prey density decreased with SRBA indicating that buildings had a negative impact on prey. Breeding success was also negatively related to SRBA. We suggest that magpies adjusted territory size according to the length of building perimeter due to a decline in prey density. As prey density declined, artificial pavement area was added to include open trash bins, which increase the availability of anthropogenic refuse such as discarded food. Vegetation area declined as prey density increased, but changes in vegetation area were minor and had little impact on prey availability measured at ground level. Structural cues were not used to adjust vegetation area, and artificial structural cues were not used to adjust territorial size over direct monitoring of prey density.