Effect of weather conditions on spring migrating Eurasian teals (Anas crecca)

Weather conditions experienced during migration are expected to influence bird movements and their timing of arrival. We analysed satellite-tracking data from Eurasian teals (Anas crecca) fitted with Argos tags in three wintering Italian sites in order to define the migratory strategies of the species. We determined the course, speed and duration of spring migratory movements, together with the number and length of stopovers made along the route. Most of the tracked teals left the wintering grounds in FebruaryMarch and reached the breeding sites located in North-Eastern Europe in May. Along their migratory route most birds stopped for several weeks at stopover sites, especially at the very beginning of migration, and this led to a slow overall migratory speed. We then focused on investigating the effect of a series of environmental cues on teal’s migratory strategies. The analysis mainly aimed at assessing if temperature and winds experienced during teal’s sojourn in an area could have had an effect on its decision to leave their wintering grounds and the stopover sites. Given that teal are small ducks and not diving ones, they need shallow water areas to feed which may freeze quite easily when temperatures decrease, so it can be hypothesized that temperatures may be a relevant cue for this species. We tried different models using different time windows, aggregate statistics and response functions, running distinct analysis for wintering and stopover sites. As expected, our data indicate that weather conditions, and especially temperature, affect migration movements, but, as already noted for other Anseriformes, this effect was mostly evident once the migration had started. Under the observed conditions, wind, on the other hand, did not seem to play a major role in teal’s decision to leave or not an area.