A NEW study, exploring the causes of population change in upland waders, has found that no single cause is connected with recent decreases in populations.
Instead, research by the RSPB, suggests that different factors associated with varying land use may be influencing changes in certain species.
Dr Murray Grant, a principle conservation scientist with RSPB, said: “The decline of uplands waders has been a cause for concern for a number of years, particularly as the reasons for these changes were not clear cut.
“These are birds that many people will recognise and were common place three or four decades ago,” he continued.
“This new research provides useful indicators on which factors might be important in driving declines in these splendid birds. The next task will be to use this information to dig a little deeper and determine the mechanisms for the declines and what we can do to help these species on areas where decreases are greatest.”
In the first country-wide assessment of its kind – which included survey plots in Lewis and Harris – the study looked at five wading bird species: lapwing, curlew, golden plover, dunlin and snipe; and explored changes in their populations across various upland habitats.
It found that where declines had occurred, they were linked with factors such as habitat cover, forest edge exposure, grouse moor management intensity and crow abundance.
Wading birds are often found on areas of damp, wet moorlands and rough grasslands, feeding on the worms and insects found in the ground. They were once a common sight on farmland and uplands, regularly cited in literature and complimented for their evocative calls and charismatic behaviour.
However, in recent decades these birds have suffered dramatic population declines in many areas.
The Repeat Upland Bird Survey carried out by the RSPB suggested declines of over 50% of lapwing, dunlin and curlew over the last 25 years in many parts of the British uplands. These losses have prompted further investigation by conservationists to try to identify the reason behind them.
Using the data from these past upland bird surveys, RSPB scientists, with support from Scottish Natural Heritage (SNH), were able to analyse changes in the abundance of waders from almost 1,500sq kilometres across the UK’s uplands.
And the results, published in the international scientific journal Bird Study, found that numbers of golden plover and snipe, declined more in upland landscapes where there was more forestry in the surrounding areas.
The exact causes for this relationship are not known, but waders breed on the ground and as such are vulnerable to predation. The surrounding forest may well be beneficial to nesting crows or foxes, which are the main predators of eggs and chicks of upland waders.
Other recent studies have shown that changes to upland water abundance can be influenced by numbers of predators, and this study suggests that afforestation, in some areas, might be an important factor.
Declines in lapwing numbers were greatest in areas dominated by heather. For this species, links to predation were also identified.
Regionally, lapwing populations fared better on areas with more intensive grouse moor management (a management practice involving predator control and heather burning) and worse where there was high crow numbers.
The same was not true however for golden plover, which surprisingly suffered greatest declines in areas where grouse moor management was more intensive.
As Professor Des Thompson for SNH commented: This research shows the complex nature of changes in our wader populations in the uplands, including vividly revealing the decline in curlew and lapwing numbers.
“Many people working in the uplands lament the loss of these birds, so we do need to intensify our understanding of what is happening – and then try to do something about it.”