Differential post-fledging survival of great and coal tits in relation to their condition and fledging date

摘要: Summary 1 We present a multivariate model of the post-fledging survival juvenile great and coal tits (Parus major L., P. ater L.) in relation to chick body condition timing breeding. Radio-telemetry colour marks were used track tit families during 20 days from fledging, that is, period dependence. Data on 342 chicks 68 broods obtained. 2 Forty-seven per cent juveniles died observation period, predation being main cause mortality. In first 4 days after fledging mortality rate was 5–10% day. 3 Survival positively correlated with mass. Furthermore, strongly decreased season. second half June, five times mid-May. The differential resulted selection for both early high Juvenile less important birds had fledged Their rates exceeded 70% all weight classes, whereas late only heaviest individuals survived equally well. poor below 20%. Thus, mass much stronger season than broods. 4 We conclude impact leaving nest results breeding and, particularly season, This may explain why earliest have been found produce most recruits into population even if they did not profit maximum food availability nestling period. On other hand, energetic limitations constrain begin egg laying adult birds. counteracting evolutionary responses seasonal development (the caterpillar peak) risk peak mortality) focused optimal reproduction narrow time-window.