New study into the dotterel's reduction

The dotterel breeds only on the highest mountain tops of Scotland and, as such, their presence offers a good indicator of the health of Scotland’s mountain landscapes.

Dotterels winter in North Africa and return to their breeding grounds on mossy plateaus on the highest mountains of Scotland from April.

Britain is at the south-western extent of the dotterels’ range. The population occupies breeding grounds eastwards from Scandinavia towards Siberia.

The dotterel is unusual in that it turns the tables on traditional gender roles. The brightly-coloured females lead in courtship before leaving the smaller, drabber males to incubate the eggs and raise the young, and for this reason the species has been counted by the number of breeding males rather than pairs. There are only about 510-750 breeding males in the Uk.

A new study published by Global Change Biology explores the potential ways that changing environmental conditions may be driving the decline and has found limited evidence that the decline in breeding is driven by climate change of dotterels.

It research focuses on snow cover and nitrogen deposition. The amount of snow-cover is important for cold-adapted species of plants and animals.

Fewer snow patches, around which dotterel feed, may lead to a reduction in peak insect abundance for chicks and cause unsuitable higher vegetation.

Higher deposition of nitrogen tends to result in a reduction of alpine specialist plants, including species of mosses that form key breeding habitats for dotterel.

Population declines and site abandonment by dotterel in Scotland during the last three decades have largely occurred at lower elevations, suggesting climate change may be the cause.

However, the new study found relatively limited evidence that the decline in the breeding population is being driven by climatic factors on the breeding grounds, despite it previously being mooted as the primary reason.

"Climate change and anthropogenic nitrogen deposition are widely regarded as important drivers of environmental change in alpine habitats. However, due to the difficulties working in high-elevation mountain systems, the impacts of these drivers on alpine breeding species have rarely been investigated," the study said.

"The Eurasian dotterel (Charadrius morinellus) is a migratory wader, which has been the subject of uniquely long-term and spatially widespread monitoring effort in Scotland, where it breeds in alpine areas in dwindling numbers.

"Here we analyse data sets spanning three decades, to investigate whether key potential drivers of environmental change in Scottish mountains (snow lie, elevated summer temperatures and nitrogen deposition) have contributed to the population decline of dotterel.

"We also consider the role of rainfall on the species wintering grounds in North Africa.

The study said: "We found dotterel declines in both density and site occupancy of breeding males primarily occurred on low and intermediate elevation sites.

"High-elevation sites mostly continued to be occupied, but males occurred at lower densities in years following snow-rich winters, suggesting high-elevation snow cover displaced dotterel to lower sites.

"Wintering ground rainfall was positively associated with densities of breeding males two springs later.

"Dotterel densities were reduced at low and intermediate sites where nitrogen deposition was greatest, but not at high-elevation sites.

"While climatic factors explained variation in breeding density between years, they did not seem to explain the species uphill retreat and decline.

“We cannot rule out the possibility that dotterel have increasingly settled on higher sites previously unavailable due to extensive snow cover, while changes associated with nitrogen deposition may also have rendered lower lying sites less suitable for breeding.”