Evolutionary trends and extreme cases of life history traits in the Blue Tit (Parus caeruleus) on oceanic islands (Canary Islands)

Aims: In order to discern principal evolutionary trends in the Canary Island blue tits (Cyanistes teneriffae) this study provides the first comprehensive description of the main life history traits for this passerine bird in the most important habitat types (laurel forest, pine forest and Phoenix / Tamarix community) on two contrasting islands (i.e. Tenerife and Fuerteventura).

Location: one study site on pine forest and laurel forest of Tenerife and one location on Phoenix Tamarix on Fuerteventura (Canary Islands).

Methods: 250 nestboxes were monitored from December to July (2000 - 2004) and the following parameters were collected: the date of laying (i.e. day of first egg), clutch size (number of eggs laid in a clutch), breeding success (hatched young-dead in nest/eggs laid x 100), second clutches (laid in the same nestbox from which a brood of young had already fledged successfully), percentage of second clutches (number of females that laid a second clutch/ number of females that laid a first clutch x 100). Data on nestling weights were obtained daily in the laurel forest of Tenerife during the breeding season of 2002. In the pine forest of Tenerife (year 2002) birds were caught in the boxes when nestlings were c. 8 days old. These were aged in two classes: first year and older birds, based on plumage characteristics.

Results: When compared with data across the entire range, the Canary Island blue tit was similar in weight and growth pattern, but revealed extreme cases of life-history traits such as the earliest mean laying date (3 February, Fuerteventura), the lowest mean clutch size (4.0 +/- 0.88 eggs, Tenerife laurel forest), and the highest percentage of second clutches (40.8 % Tenerife laurel forest).

Conclusions: Our study suggests that the laurel forest seems to be the optimal habitat for this species in terms of chick productivity. We provide evidence, inferred from our data, that this low reproductive rate was counterbalanced by high adult survival and greater longevity. Therefore, tits on these islands have evolved trends often found on oceanic islands as a consequence of a severe insular syndrome. This study supports the new taxonomic status of the N African / Canary complex (i.e. Canary Island blue tit Cyanistes teneriffae).