A short-term study of the effects of algal mats on the distribution and behavioural ecology of estuarine birds

Abstract

The effects of algal mats on wintering wading bird distribution and behaviour were studied at two sites during 1998/99 to identify changes that occurred during the winter breakdown of the algal mat. Numbers of Black-tailed Godwit Limosa limosa did not increase as the algal mat reduced in extent but a significantly greater number of birds were observed in areas without algal cover than in areas with mats in most months. The use of clear spaces, created between the algal patches as the mat broke down, by Black-tailed Godwit increased across the winter. We suggest that algal mats may physically interfere with the deep probing action of this wader. In contrast, when algal mats were most dense in November 1998, significantly greater numbers of Redshank Tringa totanus were observed in algal areas at one site. Redshank appeared not to be deterred by algal cover and, at times, preferentially utilized the algal infauna as prey.