Nestling growth of Great Tits Parus major with comparison among altitudes

Abstract

Fledgling mass can have great influence on individual’s life history and reflects the availability and quality of food in the breeding territory. Thus growth curve is used to compare the difference in the quality between different ecological conditions. The aim of the study was to fill the knowledge gap on nestling growth in Great Tit in Slovenia, to determine the influence of altitude on it and to present a tool for estimating age of nestlings and key dates in breeding phenology of Great Tit. Great Tits young were monitored using nest-boxes at three locations between years 2010 and 2012. At two locations nest-boxes were placed on three separate altitudinal belts. Weight growth curve was compared with the curves from other parts of Europe. Growth curve from Slovenia differs in growth parameters from other European populations but falls within their range. Difference in growth parameters betweenseparate populations probably comes from the difference in ecological conditions. When comparing three altitudes weight parameters of hatchlings were similar at lower and middle but different at upper altitudes indicating that weigh growth changes with the altitude. Lower food abundance that comes with rising altitude may be offset by lower competition through lower breeding density (hence similar growth parameters in lower and middle altitude), but not past certain altitude. Weight parameters are usefulwhen comparing different populations, but wing-length is better in determining the age of young in the nest.