A tale of two tails:asymmetry in Great Grey Shrike(Lanius excubitor)

Background: Asymmetry in the wild is a controversial, and to date, unresolved subject.Fluctuating asymmetry(FA) is the developmental instability(intra-individual variation) while, directional asymmetry(DA) expresses the asymmetry of the population mean.Methods: We analysed 63 Great Grey Shrike(Lanius excubitor) skins at the Naturalis Biodiversity Center, Leiden, the Netherlands.The black markings on the tails were digitized in order to evaluate the symmetry of the two sides of each shrike.Ptilochronology helped understand if nutritional condition affected symmetry.Results: ANOVA revealed no significant differences in size of the tail between sexes(F = 1.67, p > 0.05).However, there was significant difference in the shape of the black area in feathers between the sexes(F = 2.14, p < 0.05), and males had more elongated and slender black areas.Further, DA was observed only in males, but FA was noted in both sexes.Spearman correlation showed no significant association between FA score and tail features in both the sexes.However, in females, we observed a negative significant correlation between the number of fault and growth bars.The shape of the black area in the tail displayed no statistically significant association with the tail features in both sexes although growth bars influenced tail shape more than the number of fault bars.Conclusions: We concluded that the characteristics discovered by us need to also be checked in the field and if they can be used to sex individuals.Also, chromatic manipulative studies are require to verify if DA influences sexual selection in the Great Grey Shrike.

Candidate genes have sex-specific effects ontiming of spring migration and moult speedin a long-distance migratory bird

The timing of major life-history events, such as migration and moult, is set by endogenous circa-dian and circannual clocks, that have been well characterized at the molecular level. Conversely,the genetic sources of variation in phenology and in other behavioral traits have been sparsely ad-dressed. It has been proposed that inter-individual variability in the timing of seasonal events mayarise from allelic polymorphism at phenological candidate genes involved in the signaling cascadeof the endogenous clocks. In this study of a long-distance migratory passerine bird, the willowwarbler Phylloscopus trochilus, we investigated whether allelic variation at 5 polymorphic loci of 4candidate genes （Adcyapl, Clock, Crebl, and Npas2）, predicted 2 major components of the annualschedule, namely timing of spring migration across the central Mediterranean sea and moultspeed, the latter gauged from ptilochronological analyses of tail feathers moulted in the Africanwinter quarters. We identified a novel Clockgene locus （Clock region 3） showing polyQ polymorph-ism, which was however not significantly associated with any phenotypic trait. Npas2 allele sizepredicted male （but not female） spring migration date, with males bearing longer alleles migratingsignificantly earlier than those bearing shorter alleles. Crebl allele size significantly predicted male（but not female） moult speed, longer alleles being associated with faster moult. All othergenotype-phenotype associations were statistically non-significant. These findings provide newevidence for a role of candidate genes in modulating the phenology of different circannual activ-ities in long-distance migratory birds, and for the occurrence of sex-specific candidate gene effects.