Patterns of abundance, body-mass dynamics and habitat use of the reed warbler Acrocephalus scirpaceus in two reedbeds of south-eastern Spain

Abstract

The abundance, vertical distribution and body mass of the Reed Warbler were studied in two reedbeds of different structure and composition at Hondo Natural Park, south‐eastern Spain during the breeding and non‐breeding cycle in 1992–1993. Adult abundances showed similar patterns in both reedbeds, with two initial peaks in the first half of May and the second half of July. Juveniles however showed asinchronous cylcles, possibly as a result of a delay in the incubation period in the dense reed. The birds’ abundance was related to breeding activity, expressed as the percentage of birds with brood‐patch, since catches declined when birds had brood‐patches. Weight of adult birds was positively correlated with fat‐score, bill volume and tarsus‐length, whereas in juveniles body mass was correlated with fat and feather‐length. The seasonal changes in body masses were similar in both adults and juveniles, with the greater mean weights obtained in the autumn months. The patterns of habitat use showed that the vertical distribution of birds differed between the two reedbeds studied. Reed Warblers occupied mainly the upper levels in the densest reedbeds and the middle layers in the cleared reedbeds. © 1995 Taylor & Francis Group, LLC.