This report provides a better understanding of the evidence for water quality change being a potential driver of declines evident in some waterbird populations. It updates a previous review by Burton et al. (2002).

Populations of Afro-Palearctic migrant birds, which breed in Europe but winter in Africa, have shown severe declines in recent decades. To identify the causes of these declines, accurate measures of demographic rates (e.g. the number of fledglings per season, estimated survival from year to year, and immigration from other populations) are needed to allow effected targeting of conservation and research activities. A new study by the BTO and the University of Lancaster focused on the Whinchat population of Salisbury Plain (Wiltshire), which has remained relatively stable against the declining European trend. From 2010 to 2014 Whinchats were studied in detail to measure demographic rates. Adults and nestlings were colour-ringed to calculate survival rates for adult and first year birds, while nests were found and monitored to measure breeding success. Intensive surveys to census Whinchats and re-sight colour-ringed birds were also carried out each year, which allowed natal and breeding dispersal to be calculated, i.e. how close to their previous year’s hatching site or nest site, respectively, Whinchats return. These demographic rates were then used to build a population model to show how both on-site and external factors contribute to population change. Surprisingly, considering the relative stability of the population, the study identified low seasonal breeding success due to nocturnal predation and low apparent first year survival. This indicated a declining population trend. However, this trend was not reflected in the observed census counts, suggesting that high immigration from other UK breeding populations was probably balancing this decline. The study demonstrates the potential of high quality breeding habitat, such as that on Salisbury Plain, to lower the rate of population decline. However, due to this population’s reliance on immigration, it will remain vulnerable in the future if the decrease in the wider UK population continues to reduce the pool of potential newcomers. The results suggest that focusing conservation action on improving breeding success is likely to be an important immediate conservation strategy for Whinchats in Europe. In the long term, greater research emphasis is needed on migrant birds generally, as well as the factors that influence their immigration. It should also concentrate on separating first year fledglings’ dispersal and survival rates. Lastly, and importantly, it should focus on understanding the relationship between changes in demographic rates and the population trend in Whinchats, which could have implications for the conservation of wider Afro-Palearctic migrants as a whole.

Continuous cover forestry (CCF) systems are increasingly advocated for stand management, with biodiversity among the ecosystem services perceived to benefit. However, long term (>100 years) influences of such silvicultural systems on biodiversity in managed forests are poorly understood. Timed point counts in Scots pine forests in Scotland were used to quantify associations between species richness, diversity and abundance of breeding birds and different forest structures provided by CCF. Managed forests with old growth features (some including particularly old pines and snags) were considered surrogates for long term CCF stands. A stand category with an understorey of young trees (understorey reinitiation) was the most species rich (other categories in descending order were old growth, commercially maturing stands with no regenerating understorey and exclusively pre canopy-closure young growth stage) but differences were small and marginally non-significant. Heterogeneity in canopy layer structure at a scale typical of many song bird territories (ca 1 ha) and the occurrence of old growth features were associated with greater abundance in a number of individual bird species but many associations were species-specific. Knowledge of species-specific responses to forest structure can inform management for the benefit of species of conservation concern and other priority species but requires better understanding of optimal structural mosaics including frequencies of old trees and snags for those species and groups. Bird distributions can change in response to extrinsic factors within the expected long-term plans for CCF managed forests; the contribution of structural mosaics to the resilience of forests in supporting a changing avifauna deserves further attention.