Greenshanks Tringa nebularia and long‐term studies of breeding waders

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Abstract
Despite great variation in breeding, social and migration systems, there have been few long‐term (more than 5 years) studies of waders. This paper describes a 27‐year study of breeding Greenshanks Tringa nebularia, and briefly reviews the scope for long‐term work on breeding waders in the Western Palaearctic.Between 1964 and 1990 a Greenshank population in NW Scotland varied threefold in number but declined during the 1980s. Some territories were occupied almost every year whereas others became unoccupied. The increase up to the mid 1970s coincided with good summer weather likely to improve breeding success and subsequent adult recruitment. The decline occurred despite no adverse change in weather, an increase in over‐winter numbers on British and Irish estuaries, and no increase in nest predation. Afforestation in the Flow Country of northern Scotland may have exacerbated the decline by reducing numbers of potential recruits from what were once productive areas. Habitat for broods has deteriorated considerably in the study area because of the impact of all‐terrain vehicles: pool complexes have deteriorated to a greater degree in unoccupied than in occupied territories. Territories with most disturbance have been occupied less regularly. There has been a decline in habitat structural complexity likely to render chicks more prone to predation and less likely to find preferred food. Habitat is now set to recover, and predictions are made about the Greenshank's response.Of 47 wader species breeding regularly in the Western Palaearctic, none have had lifetime reproductive success measured and long‐term population dynamics have been studied in only nine. We provide a list of species that might be appropriate for addressing six important ecological issues. Five emerge as common targets for further long‐term work: Dotterel Charadrius morinellus, Lapwing Vanellus vanellus, Avocet Recurvirostra avosetta. Common Sandpiper Actitis hypoleucos and Curlew Numenius arquata.