To be or not to be a specialist: feeding and refuelling by reed warblers in Portugal

• Main Author: Silveira, André Filipe da Conceição
• Other Authors: Ramos, Jaime
• Format: Master Thesis
• Language: English
• Published: 2013
• Subjects: Passeriformes do Palearctico; Caniçais; Estratégias migratórias; Stopover; North Atlantic; North Atlantic oscillation
• Online Access: http://hdl.handle.net/10316/24904

Dissertação de mestrado em Ecologia, apresentada ao Departamento Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra. Reed beds are associations of hydrophyte vegetation that includes species of different families. They are also the natural habitat of specialized fauna such as migratory passerines who make stopovers during their migration between Europe and sub-Saharan Africa. This study assesses the quality of two reed beds in Central Portugal, Paul do Taipal and Paul da Madriz, for two insectivore passerine species, Acrocephalus scirpaceus (Reed Warbler) and Acrocephalus schoenobaenus (Sedge Warbler), similar in physiology but with contrasting migratory strategies and feeding habits. Ringing data from 12 years was used to evaluate habitat use for both study species and to determine productivity of breeding Reed Warblers. Environmental factors were used to explain stopover duration and body weight variation during spring and autumn migration. The birds' body condition was assessed and compared between species, seasons and age. Blood samples were taken to assess triglycerides and glucose blood levels, which are considered to distinguish migratory strategies. Abundance of food items present in the environment was determined by counting arthropods in the field to determine possible differences in stopover quality, with emphasis on the Sedge Warbler's preferred food, Hyalopteris prunis aphids. Finally, bird faeces were collected and examined to assess bird diet and preference in both reed beds. This study shows that Paul do Taipal was used more extensively than Paul da Madriz for both species. North Atlantic Oscillation and Northern Annular Mode values between December and March were the environmental parameters more correlated with stopover duration for both migratory seasons, whereas precipitation in North Africa and wind speed in Portugal were the most important parameters to explain body weight variation in spring and autumn migration, respectively. The body condition of Reed and ...