Factors affecting the use of estuarine areas by waders : implications for their conservation

• Autor(es): Dias, Maria P.
• Data: 2009
• Identificador Persistente: http://hdl.handle.net/10451/1590
• Origem: Repositório da Universidade de Lisboa
• Assunto(s): Estuários; Comportamento alimentar; Límicolas
• Tipo de Documento: Tese de doutoramento
• Idioma: Inglês
• Orientador(es): Palmeirim, Jorge Manuel Mestre, 1950-; Granadeiro, José Pedro
• Contribuidor(es): Repositório da Universidade de Lisboa

Descrição

Tese de doutoramento em Biologia (Ecologia) apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2009

Estuarine intertidal flats are amongst the most important habitats for waders during the non-breeding season. These environments face increasing pressures from human activities, which are contributing to a general decline in wader populations. It is therefore essential to know the factors driving the use of intertidal flats by wintering waders, particularly their implications to the conservation of these species. The analysis of such factors was the main focus of this thesis, what was attained by answering several specific questions related with the use of sediment flats at different spatial scales, using the waders wintering in Tagus estuary as model. It was demonstrated that dunlins Calidris alpina avoid performing long flights between roost sites and foraging grounds, what highlights the importance of the maintenance of a network of good-quality roosts for waders in estuarine areas. It was also shown that species vary in their response to the tidal movement, what has large implications in the estimates of use of tidal areas. Upper tidal flats (which are under considerable threat due to their proximity to shoreline) proved to be particularly important in providing food resources for waders. The fine scale use of tidal areas was studied by testing several predictions related with the searching behaviour of waders. It was shown that only tactile species, as black-tailed godwits Limosa limosa, are expected to present an arearestricted search, a type of movement usually adopted by foragers in clumpy environments. Finally, it was evaluated the impacts of traditional shellfishing on waders. Current levels of shellfishing seem to be compatible with the preservation of the Tagus estuary as a key site for waders, but the predictable increase in disturbance due to urban expansion in the vicinity of the Tagus estuary can result in serious impacts on some wader species.

Fundação para a Ciência e Tecnologia (SFRH/BD/19313/2004); projectos Sat-Tagis (PDCTM/C/MAR/15256/1999) e Pred-Tagis (POCTI/BSE/47569/2002)