Nestling growth and breeding biology of great tit, blue tit, willow tit and crested tit

Abstract

The correlative relationship of growth rate constant, environmental variables and life history traits was studied in the nestlings of the great tit, the willow tit, the crested tit and the blue tit in the Oulu area of northern Finland in 1969, 1977–1981 and 2017. All the species reached their species specific asymptotic weights by the age of 13–14 days. The asymptotic weight of the great tit was relatively lower than the adult weight compared with the other parids studied. The mortality rate of the nestling great tits was higher than of the crested and willow tits in 2017. Large intial brood size pose an negative imapct on the great tit mass growth. It is possiblely related to the high energy maintainence from the parents and unpredictable weather reduces food supply. The high number of hatchlings seems to be related to increasing nestling mortality in the great tit. After the brood reduction, parents can better nourish the rest of the nestlings which leads to a positive association between the number of fledged chicks and the growth rate constant. We did not find any significant relationship between the ambient temperature and growth rate constant in any of the species. It can be associated with the method of collecting the temperature data. However, the amount of rainfall during the nestling period was positively related to the wing growth rate constant in great tits. The late hatched willow tit nestlings grew faster than the early nestlings. There was a trade-off for the timing of breeding in the willow tit. The early nestling might be able to prepare themselves into breeding population while the late nestling might receive better nourishment from their parents. Besides, the brood size at hatching were markedly related to the growth rate constant in the willow tit. This possibly reflects the female quality and habitat quality in the Oulu area. The growth rate constant of different species was related to the body size, clutch size, and species specific breeding strategies.