Decline of a montane Mediterranean Pied flycatcher Ficedula hypoleuca population in relation to climate

González, Sonia; Sanz, Juan Jose; Moreno, Juan

26 June 2017

Certain populations of long-distance migratory birds are suffering declines, which may be attributed to effects of climate change. In this article, we have analysed a long-term (1991-2015) data set on a Pied flycatcher (Ficedula hypoleuca) population breeding in nest-boxes in a Mediterranean montane oak forest, exploring the trends in population size due to changes in nestling recruitment, female survival and female immigration. We have related these changes in population parameters to local climate, winter NAO index and to breeding density. During the last 25 years the population has declined by half, mainly in association with a decrease in nestling mass and structural size which had repercussions on the probability of nestling recruitment to the population. Lower local nestling recruitment in certain years was linked to lower female immigration rate in the same years. On the other hand, the local survival of females remained stable throughout the study period. Laying date and breeding success were negatively affected by local temperatures while breeding, recruitment rate likewise by minimum temperature prior to breeding in April. As minimum April temperatures have increased across the study period, this may have affected recruitment and immigration rates negatively. On the other hand, tarsus length and body mass of nestlings were positively associated with winter NAO index, pointing to more global climatic links. Moreover, there was also a negative temporal trend in body mass of adults, implying increasingly difficult conditions for breeding. Declining recruit production in the study area could be attributed to a mismatch between the timing of arrival and breeding in the population, and the peak of food availability in this area.