A scientific paper, just published in the Journal of Ornithology, written by scientists from the RSPB Centre for Conservation Science, suggests that the whinchat population in the UK uplands is not currently limited by the availability of apparently suitable breeding habitat. Conservation Scientists, Andrew Stanbury and Irena Tománková explain more.
Declining whinchat
Over the last century, breeding whinchat have been lost from the UK lowlands, probably because of changes in grassland management as a result of agricultural intensification. Those that remain are now largely found in unenclosed areas of semi-natural grassland and heath in the uplands; but the population here continues to decline. Our study focused on these key habitats.
The overall decline of whinchat in the UK between 1994 and 2019. Blue dots are the annual population index estimates, the dark green line is the smoothed population trend, and the light green band is the 85% confident intervals around the smoothed trend © BTO/JNCC BirdTrends Report
As a long-distance migrant, potential causes of whinchat decline are diverse and may act on a single part, or interact between different parts, of their migratory cycle; however, studies suggest that they are not currently limited by resource availability on their sub-Saharan non-breeding grounds and conservation effort should remain focussed on their breeding areas.
Our paper
To explore the potential influence of habitat availability in the UK uplands, we visited over 230 whinchat territories within semi-natural grassland, heath, bog and scrubland, and compared the habitats found here with unoccupied locations nearby. Whinchat territories were characterised by having higher Bracken cover, low density of trees and closer proximity to valley bottoms. Upland valley systems appear important and may provide sheltered, warmer micro-climates that whinchat favour.
We then used this information to predict whinchat occurrence at a range of other sites and compared that to what we found during systematic bird surveys. We estimated that less than 50% of apparently suitable habitat was occupied by breeding birds. Our findings are consistent with an earlier study which estimated that most of the highly suitable, extensively managed lowland grassland was unoccupied on Salisbury Plain; a site that still holds a significant whinchat population.
Limitations of the study
There are, however, a couple of caveats. Firstly, our findings apply only to the upland habitat types we studied- unenclosed semi-natural grassland, heath, bog and scrubland; and not enclosed farmland, for example, in the lowlands. Secondly, our work does not exclude the influence of habitat condition, prey availability or other environmental and climatic variables as potential contributory factors in whinchat decline, even within areas that were deemed apparently suitable.
Another recent study implicates low recruitment, particularly poor breeding productivity and juvenile survival, as a key factor driving the large-scale population decline in Europe. Further evidence is needed into how habitat and other environmental factors influence whinchat recruitment, particularly breeding productivity, in the UK uplands, so ideally measures can be developed to help enhance it.
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