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RSPB announce drastic decline in one of UK’s rarest breeding ducks

45% drop in common scoter population since 1995.

The UK’s most threatened breeding duck has suffered drastic declines over the last decade with their population nearly halved, according to alarming new survey results.

Common scoters – plump, jet black diving ducks with long tails and bright yellow beaks on the male – have experienced marked reductions in their UK range, with the remaining breeding population now restricted to isolated and remote freshwater lochs of northern Scotland.

The species has been surveyed nationally once in 1995, and the 2007 national count was conducted to assess changes in common scoter numbers in the intervening years. Just 52 pairs were recorded in 2007, compared with 95 pairs in 2005 – a 45% drop in their numbers.

The survey was a partnership between the RSPB, Scottish Natural Heritage (SNH) and the Wildfowl and Wetlands Trust. Fieldwork was conducted by four RSPB scoter surveyers working alongside RSPB regional and reserve staff, a team of WWT surveyors and other volunteers.

Factors driving the reduction in the breeding populaton are unclear and more research is needed to determine the precise causes, however there are several possibilities.

The highest declines have been in the south and west of their British range; they have been lost completely from Loch Lomond and in North Ireland, so it is possible that changes in the climate could be pushing the birds further north.

Plantations and inappropriately sited forestry in the Flow Country of North Scotland may have led to changes in the water chemsitry of some freshwater loch stystems causing invertebreate populations to shift. This could be restricting food availability and making it more difficult for them to thrive in their historical territories.

Elsewhere predatory species such as pike have been introduced in some of the lochs where scoters used to breed and this could be responsible for higher chick mortality restricting their breeding success. However, some scientists believe that pike might actually help common scoters by predating smaller fish which compete with the ducks and their offspring for the invertebrates in the water systems.

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