Effects of the February 2012 cold spell on terrestrial birds wintering in France

Abstract

We document the mortality of terrestrial bird species wintering in France as a result of the 2012 February cold spell. We describe the range of species affected and how some of them reacted to the cold spell in term of movement and variation in body mass. Mortality records concerned 1,791 individuals from 42 species. Among terrestrial birds, Northern Lapwings Vanellus vanellus, Eurasian Woodcocks Scolopax rusticola and thrush species suffered the most from the cold spell. Among casualties, 56% of birds starved to death and 8.4% were predated. Collisions with vehicles accounted for 23.7% of deaths for all species, and reached 50% for Lapwings. Location of mortality records suggested that Lapwings and Woodcocks moved en masse towards the south and southwest of France to escape from the cold spell. Body mass of thrushes, Lapwings and Woodcocks birds was rapidly depleted because birds could not access food resources. On average, birds which were 30% lighter than birds weighed at the same period during normal winters had reached a lethal body mass. The results of this enquiry highlight the impact of such cold-weather events and the need, in particular for game bird species, to promote standardised enquiries on mortality when severe winter events occur.