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11.
Balázs?RosivallEmail author János?T?r?k Dennis?Hasselquist Staffan?Bensch 《Behavioral ecology and sociobiology》2004,56(4):346-351
Recently, a number of studies have found adaptive brood sex ratio (BSR) manipulation in birds. The reason for such manipulations is thought to be the different reproductive value of male and female nestlings. Several studies have found that parental quality and food supply can affect BSR, however results are sometimes inconsistent between species and populations. We investigated BSR patterns in a Hungarian population of Collared Flycatchers (Ficedula albicollis) and compared the results with those obtained in a previous study of the same species in Sweden. We found two significant differences. First, the male forehead patch size, a heritable, sexually selected trait, affected the brood sex ratio in the Swedish population, but not in our Hungarian study population. This difference might be a consequence of the different information content of the forehead patch size in the two populations. Second, a seasonal shift in BSR (more sons late in the season) was observed in the Hungarian, but not in the Swedish population.Communicated by J. Graves 相似文献
12.
In southern Sweden, where exposure to long range distributedheavy metals is about the highest in Scandinavia, depositionsof cadmium (Cd) and lead (Pb) decreased about 20 and 70%,respectively, between mid-1980s and mid-1990s, as estimated bytheir concentrations in moss. Concentrations of Cd and Pb in tissues of the pied flycatcher (Ficedula hypoleuca) and bank vole (Clethrionomys glareolus) were also lower in 1996and 1997 compared to 1981 and 1982. It is concluded that the decreased deposition rate of these elements in southern Sweden had caused decreased exposure, and thus also to decreased potential risk of detrimental effects on insectivorous birds andherbivorous mammals. There was no indication that breeding results of pied flycatcher was influenced by the decreased deposition of toxic metals. 相似文献
13.
Hybrid zones are often found in areas where the environmental characteristics of native habitat of both parental species meet.
One of the plausible mechanisms that maintain species distinctiveness, or limit hybridization, is the existence of local species-specific
preferences for the natal habitat type. We evaluated this hypothesis for two passerine bird species, the pied Ficedula hypoleuca and collared flycatcher F. albicollis, in their narrow hybrid zone in Central Europe. Both species have quite distinct habitat distributions, and they have also
been reported to differ in their foraging niches. In a series of aviary experiments, we demonstrated that both species show
distinct preferences for trees from their native area. The pied flycatcher preferred coniferous vegetation, while the collared
flycatcher favored deciduous vegetation. In addition, both species differed in foraging substrate preferences. The pied flycatcher
preferred to forage in the lower strata on the ground than the canopy, whereas the collared flycatcher foraged more at the
canopy level. Both males and females of each species were highly consistent in their preference patterns. Due to the widespread
nature of hybrid zones as places with transitional habitat features and the well-known habitat tight associations of various
animal taxa with particular habitat types, we propose that habitat preferences might be an important and common mechanism
that enhances the formation of conspecific pairs. 相似文献