The impact of macroalgal blooms on the use of the intertidal area and feeding behaviour of waders (Charadrii) in the Mondego estuary (West Portugal).
Data
1999
Autores
Cabral, João Alexandre
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Resumo
The present paper examined the possible impact of macroalgal blooms, among other influential factors, on prey abundance and
availability to waders, assessing the consequences for feeding behaviour and for the specific patterns of use of the intertidal areas by these birds
when macroalgal mats become dense and contiguous covering large areas of the Mondego estuary (west Portugal). Three representative
microhabitats were chosen in intertidal flats to control and evaluate the effects of various factors on waders. This study shows that foraging
waders did not seem to be indifferent to the effects of some biological factors, sediment characteristics and epistructures when selecting feeding
microhabitats. Overall, the results suggest that the predominant and constant negative effects on specific patterns of use of the intertidal
sub-areas by the majority of waders were determined by two main factors: gull perturbation and macroalgal biomass. The macroalgal blooms
assumed, by their persistence over a period of several months, a different magnitude of effect when compared with sporadic factors such as gull
presence. Contrary to the effects on distribution, macroalgal blooms do not influence negatively the feeding behaviour parameters considered.
Moreover, we were unable to prove that the presence of macroalgae on the sediment was pernicious to the wader prey organisms, perhaps
because the total amount of the area of the estuary affected by weed during the study period never exceeded 36 % and was surrounded by
important algal-free areas that ensured a healthy prey population. Nevertheless, on the long-term, an increase of dense and contiguous
macroalgal mats due to the progressive eutrophication of the Mondego estuary, covering large areas of the intertidal flats, may affect directly
or indirectly all wader species.
Descrição
Palavras-chave
Shorebirds , Waders (Charadrii) , Eutrophication , Foraging behaviour , Zoobenthos
Citação
Cabral J. A. et al., 1999