Sexual selection and blue tit (Parus caeruleus) crown coloration

摘要: Conspicuous, sexually dimorphic plumage in birds is most likely a consequence of sexual selection favouring more ornamented males at obtaining territory and/or mate. Recent comparative analyses suggest that, among socially monogamous species, extra-pair paternity has also contributed to the elaboration male ornaments. If females prefer as social or mates this could translate into strong directional for ornament elaboration, since these might sire offspring their own brood (within-pair success) broods other (extra-pair success). In thesis I study expression UV/blue crown coloration blue tit (Parus caeruleus) and investigate whether trait be selected through increased within- success. Blue tits are passerines with relatively high levels paternity, species display ultraviolet(UV)/blue reflectant feathers than females. Based on three years data found that cue used by assess age became UV-ornamented they aged. Crown coloration, however, did not correlate survival next breeding season, suggesting necessarily higher quality. While UV-ornamentation between years, it declined course year due feather wear dirt accumulation affect female perception attractiveness. However, although decline UV ornamentation winter spring was large, had no effect reproductive success, colour were still positively correlated. Using genetic analysis show do benefit within-pair On contrary, less UV-ornamented, adult sired offspring. Hence successful population resembled juveniles colour. Accordingly, seem recognise highly successful, biased sex ratio towards if paired males. The causality patterns tested manipulation experiment, where treated become (UV+) (UV-) within natural range variation. Against expectations UV(+) significantly UV(-) while proportion unaffected manipulation. Brood ratios differ treatments but depended before results plays role allocation, provide experimental support observed correlational patterns. discuss discrepancy observational data, emphasising potential problems structural Finally, given offspring, explore possibility would pairing quality High often ornamented, pair assortatively based expression. This case population, appear indicate relevant qualities (fecundity, seasonal mate any years. To conclude, seems favour older, population. Whether preference unclear. Alternatively hypothesise being may enable searching extra copulations intrude territories without eliciting aggression owners, perhaps mimicking juveniles. Detailed behavioural observations wild coupled choice chamber experiments captivity necessary test idea.