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White patches in the Painted Redstart (Myioborus pictus) are adaptations to flush prey during flush-pursue foraging which is characteristic for this species. Conspicuousness of white wing patches was measured in terms if time needed for a human observer to find a taxidermic model in a natural habitat. The time to find a model without patches did not differ from the time to find a model with white patches, indicating that white patches do not confer higher conspicuousness to non-moving redstarts. The results are discussed in terms of predation risk from such visually orienting predators as hawks or pygmy owls, and in comparison to other Myioborus species, all which do not posses the white wing patches.
Models of optimal search rates predict that predators increase the search rate when availability of conspicuous prey increases relative to cryptic prey. I tested this prediction by comparing foraging hop rates by 19 Painted Redstarts (Myioborus pictus) - insectivorous birds in Arizona, USA. Redstarts often use flashy displays of open wings and tail to flush their prey and to subsequently chase the prey in air. Such flush-displays make the prey conspicuous and easy to detect. Hence, foraging mode affects relative availability of conspicuous versus cryptic prey: birds foraging with frequent flush-displays encounter conspicuous prey more often then birds foraging with infrequent flush-displays. As predicted, the hop rates during foraging with infrequent flush-displays were lower than hop rates during foraging with frequent displays.
This is the first quantitative report of the composition of mixed flocks of wintering birds in the temperate forests of Asia. There were nine species observed in the 37 mixed flocks: Parus varius, Parus major, Parus palustris, Parus ater, Aegithalos caudatus, Regulus regulus, Sitta europaea, Dendrocopos kizuki, Dendrocopos major. For each species the proportion and the average number of individuals are presented in four forest types: fir, pine, oak and mixed forest consisting mainly of oak and pine. P. major was seen in a higher proportion of flocks in coniferous (pine and fir forests combined) than in deciduous (mixed and oak combined) forests. P. ater used coniferous trees more often than P. major and more often than P. palustris.
The avifauna of three botanical gardens near Seoul was studied. Total number of species in the gardens (16-20) is within range observed in Europe. Total densities of birds observed (66-160 ind./10 ha) were in lower range of the densities in urban parks and wooded areas in Europe. This is the first such report for temperate East Asia.
The wintering mixed flocks of tits (Paridae) and associated birds, are good objects for studying ecological niche division. In this respect the mixed species flocks on the Asian continent are poorly studied in comparison to European and North American ones. In this report we describe spatial distribution of foraging sites of eight bird species in 39 winter flocks near Seoul, Korea: Varied tit – Parus varius Temminck & Schlegel, Great tit – P. major Temminck & Schlegel, Marsh tit – P. palustris Bianchi, Coal tit – P. ater Buturlin, Long-tailed tit – Aegithalos caudatus Clark, Nuthatch – Sitta europaea Swinhoe, Japanese Pygmy Woodpecker – Dendrocopos kizuki Taka-Tsukasa, and Goldcrest – Regulus regulus Blakiston. Foraging sites (in coniferous and mixed forests) were classified into five height layers: on the ground, <1.5 m above the ground, 1.5–4 m, 4–7m, and > 7m. Trees were divided into three horizontal zones depending on the distance from trunk: crown interior, intermediate zone, and external twigs. Species differed significantly in the use of height layers: P. major foraged mostly on the ground, P. ater and A. caudatus foraged mostly in the highest forest layer, P. palustris was often seen in bushes, and P. varius occurred in the middle tree layer. There was no clear correlation between height of foraging and species body size. However, body size played an important role for segregation in horizontal zones, and two species, the larger P.major and the smaller P. ater differed significantly in the mean distance from trunk. Species of large body size like P. varius and P. major, foraged mostly in the interior of the tree crown, while the smaller species, P.ater and A. caudatus, foraged mostly in the external zone; the intermediate in size, P. palustris, foraged equally often in each of the three zones. The sites used most often by Korean populations of three tit species, P. major, P. palustris and P. ater, were similar to the sites used by European populations of the respective species. These results represent one of a few quantitative studies on mixed species flocks in continental Asia.
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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