Energetics of Incubation by the Goldcrest Regulus regulus in Relation to Ambient Air Temperatures and the Geographical Distribution of the Species

Abstract

The total heat requirement for a successful egg hatching was calculated at 27.4 kcal, and the daily amount of heat applied to the eggs, at an air temperature of 16.degree. C, was 2.8 kcal. Mean daily air temperatures lower than 10.degree. C are increasingly unfavorable to the goldcrest''s breeding success. The northern distribution of the goldcrest in Fennoscandia appears to be limited by the air temperature during the breeding season.