ECOLOGICAL AND MORPHOLOGICAL VARIATION OF CANARY ISLAND BLUE TITS, PARUS-CAERULEUS (AVES, PARIDAE)

Canary Island blue tits have differentiated within the last million years. Compared with mainland populations they have short wings, large beaks and tarsi, and tend to be less variable in these parameters. Within the archipelago the eastern populations have the shortest wings and tarsi but the widest and deepest beaks. The eastern populations may have been derived from central island ones, following extinction of the original eastern populations during a warm period in the last Ice Age. New measurements have been used to test contrasting predictions of hypotheses that explain inter‐island morphological variation in terms of either climatic or ecological influences. Neither hypothesis is sufficient to explain the variation. A model which combines mem is proposed as follows. Mild winter temperatures have selected for small body size and wing length, especially on the hot, dry, eastern islands. On the other pine‐forested, islands, selection has favoured relatively long tarsi and long, slender, beaks for efficient foraging among pine foliage. The absence of die pine‐dwelling coal tit from the islands has facilitated mis evolutionary shift. It is shown that blue tits in pines forage more in the needles and cones on the Canary Islands than they do on die North African mainland. Copyright © 1979, Wiley Blackwell. All rights reserved