Living on the edge: Preliminary analysis of the breeding population of crested and coal tits at high elevations.
Jana Marco Tresserras
, Albert Burgas
, Bernat Claramunt López
Període de realització
2016 - En curs
Mountain environments are amongst the most threatened environments by global warming, with already evident effects (e.g. glacier melting). Studying how species are adapting to these new conditions and how they may take advantage of new opportunities is fundamental to understand the global process of climate change. Passerine birds are the most abundant taxonomic group of vertebrates in the Pyrenees, but only some species inhabit the forested lands at higher elevations, where nesting opportunities are scarce and climatic conditions are harsh. Two of these species, the crested tit (Lophophanes cristatus) and the coal tit (Periparus ater), can be found along the whole elevational gradient. The aim of this project is to monitor the fitness of these two species at the low and high distribution edges of black pine forests of the Pyrenees. In May 2016, we installed a total of 108 nest boxes at higher elevations; and 50 more were installed at the lower range in September 2017.
All nest boxes have been checked once a month from May to October, recording any sign of reproduction (nest, eggs, chicks); 11 ringing stations were settled in May 2017 (7 at high and 4 at low elevation), with ringing campaigns occurring almost daily in May-June (20 days), July (30 days), and September (20 days). When captured, adults of both species are marked, and standard morphometric measures are taken. Here we show the first results of the breeding population of crested and coal tit at the highest altitude range of the species and discuss the morphometric differences between the low and high populations. In 2017, only coal tits at higher elevation were fatter than the low elevation individuals; similarly, the expected breeding patterns (crested tits first and then coal tits) differed between 2016 and 2017, likely due to the differing environmental conditions.