Mm. Lambrechts et Pc. Dias, DIFFERENCES IN THE ONSET OF LAYING BETWEEN ISLAND AND MAINLAND MEDITERRANEAN BLUE TITS PARUS-CAERULEUS - PHENOTYPIC PLASTICITY OR GENETIC-DIFFERENCES, Ibis, 135(4), 1993, pp. 451-455
Blue tits Parus caeruleus breeding in deciduous or in evergreen woodla
nds on the mainland of Europe start to lay 3-4 weeks earlier than Blue
Tits on the island of Corsica breeding in evergreen woodlands. A simi
lar difference in average laying date between the two Blue Tit populat
ions has been found in a relatively small sample of captive birds held
in outdoor aviaries on the mainland. To provide data on the habitat c
ontrast in Corsica for comparison with that on the mainland, a new stu
dy area was started in one of the few deciduous woodlands on Corsica.
In addition, new data on laying dates of captive Blue Tits were gather
ed to increase the sample size of independent pairs in aviaries. This
study shows that the habitat effect (deciduous v evergreen woodland) o
n the average laying date of Blue Tits is relatively small in comparis
on with the geography effect (European mainland v Corsica). The laying
date differences between mainland and insular Blue Tits persisted wha
tever the type of habitat (deciduous, evergreen or outdoor aviaries on
the mainland). The data support the hypothesis that the observed diff
erences in the onset of laying between the mainland and insular Blue T
its were mainly influenced by genetic effects and relatively little by
non-genetic maternal effects of by genotype-environment interactions.