Differential autumn migration of Sedge Warblers (Acrocephalus schoenobaenus) through the Txingudi marsh (northern Spain).

Full article

Published:

Volume 46(2), December 1999. Pages 171-178.

Language:

Spanish

Original title:

Migración postnupcial diferencial del Carricerín Común (Acrocephalus schoenobaenus) en la marisma de Txingudi (N de España).

Keywords:

Acrocephalus schoenobaenus, age, aphid abundance, autumn migration, body mass increase, phenology, Sedge Warbler, stopover residence times, Txingudi.

Abstract:

This work compares the phenology, the stopover residence times and the changes of body mass between adult and young Sedge Warblers during the autumn migration in the Txingudi marsh. Migration phenology was different in both age classes. The autumn mean timing of migration and the maximum intensity of passage was earlier for adult birds (1 August vs. 12 August and 25-29 July vs. 14-18 August, respectively; Fig. 1). The proportion of adult birds retrapped was lower (11.11% vs. 18.72%) and stopped over for a shorter time than youngs (2.53 days vs. 4.2 days; Fig. 2). In contrast to youngs, adults star-ted accumulating fat earlier than youngs, their body mass on the last trapping occasion being larger (13.03 g vs. 11.92 g; Fig. 4) and the rate of body mass increase being higher (0.73 g/day vs. 0.28 g/day; Fig. 4). These results could be explained by superior feeding conditions (abundance of aphids Hyalopterus pruni) in the study area during the peak adult passage than during the peak passage of young birds (compare Fig. 1 to Fig. 5), as the rate of body mass increase was closely related to aphid abundance over time (Fig. 5).