Spring Arrival Timing Varies between the Groups of Blackcaps (Sylvia atricapilla) Differing in Wing Length

Abstract

We studied the advancement of the spring migration in a 28-year period in two groups of blackcaps (Sylvia atricapilla) differing in wing length, which is known to be a proxy for migration distance. We related this advancement to the numbers of captured blackcaps. Short-winged birds (short-distance blackcaps), in the period preceding their increase in numbers (1982–1989), advanced their spring passage more and arrived 5 days earlier at their stop-over site than long-winged individuals (long-distance blackcaps). In the second period (1994–2009) characterised by a marked increase in numbers of blackcaps, advancement of spring migration was less pronounced and in this period all blackcaps arrived at the stop-over site at the same time. We suggest that the difference in the magnitude of the response of short- and long-winged birds resembles that found between short- and long-distance migrants. Shorter distance to the breeding grounds and earlier departure from their European wintering grounds may strongly affect spring migration phenology of the former group.