Avian habitat use on the non-estuarine intertidal coast

Abstract

Non-estuarine (‘open’) coasts provide extensive and varied habitats for birds. Rocky intertidal shores, in particular, can provide abundant food resources for several species, notably waders (Feare and Summers, 1985). These resources and the bird assemblages that use them are fundamentally different in several respects to those occurring within estuaries (Chapter 12). This chapter reviews the bird assemblages that use intertidal habitats outside estuaries, habitat associations and constraining factors, interactions between the use of the open coast and supratidal and other adjacent habitats, and the impacts of recent environmental changes on avian assemblage composition and habitat relationships. The focus is on intertidal habitats and not other open coast habitats such as dune systems, coastal scrub and cliffs; this wider, highly varied range of coastal environments supports diverse assemblages of migrating and breeding birds, most notably of passerines and breeding seabirds. While the chapter primarily considers the avian assemblages that use non-estuarine intertidal habitats in Europe, in particular Britain, I also draw on studies from elsewhere in reviewing the factors and environmental changes that affect habitat use. Non-estuarine intertidal habitats and their bird assemblages The intertidal habitats found on the open coast include both soft-substrate (typically sandy) shores and rocky shores of exposed bedrock, boulders and shingle (gravel), the character of which depends greatly on the prevailing rock type and the shore’s exposure (Little et al ., 2009). Rocky shore habitats can be highly varied and complex, and in Britain, at least, may be extensively covered by beds of mussels (chiefly Mytilus edulis ), limpets, barnacles and seaweed (including brown algae such as Fucus , Ascophyllum and Pelvetia , and green algae such as Ulva ), while subtidal areas can support dense beds of kelp (e.g. Laminaria ) (Connor et al ., 2004). These habitats support a varied avifauna, both in the breeding and, notably, the non-breeding seasons – a previous review of bird species utilising rocky shores, for example, reported that a total of 47 species fed in the rocky intertidal zone at Robin Hood’s Bay, Yorkshire (Feare and Summers, 1985).