Volume 20 (2012): Issue 1 (June 2012)

Sexual selection may impose fitness costs on both males and females due to the costs of developing and maintaining exaggerated sexual signals, reducing average fitness in strongly sexually selected species. Such reductions in average fitness could affect local extinction risk and hence distribution range. However, given that both sexually monochromatic and dichromatic species are common and widespread, benefits of sexual selection must be invoked to maintain equilibrium. We tested for differences in breeding range size and population size between monochromatic and dichromatic species of birds in a comparative analysis of species from the Western Palaearctic. In an analysis of standardized linear contrasts of the relationship between sexual dichromatism and range size and population size, respectively, that controlled for similarity among taxa due to common descent, we found no significant relationship. However, when we analyzed carotenoid-based sexual dichromatism sexually dichromatic species had larger distribution areas and higher northernmost distribution limits, but not southernmost distribution limits than sexually monochromatic species. In contrast, melanin-based sexual dichromatism was not significantly associated with range size or population size. Therefore, population density of sexually dichromatic species with carotenoid-based coloration was lower than that of monochromatic species, because dichromatic species had similar population sizes but larger ranges than monochromatic species. These findings suggest that the different physiological roles of pigments associated with sexual dichromatism have effects on total range size of birds.

In a number of bird species, the sex ratio of the broods is not random, instead it is related to parental quality and environmental conditions. Several hypotheses have been proposed to explain this phenomenon, the so called sex ratio adjustment. According to these hypotheses, sex ratio adjustment is expected to evolve when the fitness benefit an offspring confers to the parents changes with ecological or social factors in a sex-specific way. Though many correlative and experimental studies support these hypotheses, there are still unresolved problems. In our paper, we provide details on the hypotheses related to sex ratio adjustment and explanations for the differences observed in sex ratio patterns between populations and years. Finally, we discuss the importance of sex ratio adjustment for species conservation.

Lice (Phthiraptera) chew characteristic holes on the remiges and rectrices of Barn swallows (Hirundo rustica). The number of these holes correlate positively with the intensity of louse infestation, hence hole counts are useful to quantify lousiness. Several papers showed that lice affect both life expectancy and reproductive success of hosts. In male Barn swallows, the length of the outermost tail feathers act as a sexual signal. Females prefer long-tailed males, which have significantly fewer feather holes. In this study we sampled breeding and migrating Barn swallows and compared their louse burden, and the relationship between tail length and the number of feather holes. We found significant negative correlation between feather holes and tail length in breeding males; however, we found non-significant correlation in migrating males. We suggest that attractive males have more physical interactions (e.g. extra-pair copulation) during the breeding season, than less attractive males, hence they are more exposed to louse transmission, and therefore the difference in the infestation declines towards the end of the breeding season. However, given that migrating swallow groups include colonial and solitary breeding birds, it cannot be excluded that a potentially different louse distribution on solitary breeding birds may contribute to the results.

A recently published checklist of Hungarian louse fauna (Insecta: Phthiraptera) listed 279 species and subspecies which have been recorded in Hungary. According to that checklist several louse species still await detection in Hungary, and many of the previously reported louse species have not been found on all expected host species yet. Our faunistical survey on avian lice started in 2005 at Ócsa Bird Ringing Station, resulting hundreds of ectoparasite samples collected from over 70 bird species. Additionally, our louse collection has grown by collecting samples in other research projects focusing on various bird species, and by sampling cadavers before taxidermy in the Bird Collection of the Hungarian Natural History Museum. As the results of a preliminary exploration of this collection, we list 20 louse species which are new to the Hungarian fauna, as well as the first Hungarian records of 17 host-parasite associations. We also found 3 louse-bird association records new for the World fauna.

The local abundance and spatial distribution of the short- to medium-distance migratory and daytime stopover passerines (Robin Erithacus rubecula, Blackcap Sylvia atricapilla, Chiffchaff Phylloscopus collybita, Blue tit Parus caeruleus, Great tit P. major) were studied in a West Hungarian stopover ground during post-breeding season. The dispergation index of all migratory bird species revealed clumped distribution both in „smallest annual capture year” (abb. SACY) and the „largest annual capture year” (abb. LACY). According to the PCA the spatial occurrences of Blackcap, Blue tit and Great tit captured in LACY showed significantly higher concentration than of those migrating in SACY. The studied species appeared in all four habitats (bushy, forest, grassland, marsh) of the study stopover area, but their clumped spatial distribution showed habitat preference. The abundance-dependent shift of habitat selection was found only in Great tit, the most of them captured in SACY concentrated in grassland with bushy, while the ones captured in LACY grouped in forest habitat type. Blackcaps were grouped the grassland with bushes habitat type where many Dwarf elder (Sambucus ebulus) bushes were available during autumn migration.