New research by the BTO and the University of East Anglia uses information from the Nest Record Scheme to investigate changes in Willow Warbler breeding between the 1960s and the present day. Despite advances in the timing of egg laying, there has been little change in Willow Warbler productivity over this period. New research by the BTO and the University of East Anglia makes use of the incredible amount of information collected by volunteers taking part in the Nest Record Scheme to investigate the consequences of shifts in timing of breeding for productivity in Willow Warblers. Using information from nearly 7000 nests collected between the 1960s and the present day, this study quantifies changes in the timing of laying dates and seasonal variation in both productivity and timing of breeding (i.e. the proportion of birds nesting at different points in the season), to assess the influence of these factors on changes to overall productivity. In both north-west Britain (where populations are stable) and the south-east (where populations have declined), Willow Warblers are laying their eggs earlier, and such early nesting attempts fledge a higher number of chicks than those laid towards the end of the season. However, these advances have not lead to an increase in overall productivity, as while the proportion of early-season nests has increased, the seasonal decline in productivity in the north-west has reduced and consequently overall productivity is stable. In the south-east, however, the seasonal decline in productivity has increased and, despite the advance in timing of breeding, overall productivity has declined. While shifts in the timing of breeding of migratory species are widespread, this study highlights that the consequences for breeding success at the population-scale will depend on both the seasonal pattern of nesting dates (which will be influenced by the dates that birds arrive from their wintering grounds, environmental conditions for breeding, nest failure and re-nesting) and on seasonal variation in productivity. This means that despite breeding success often being highest at the start of the season, advances in laying dates do not necessarily lead to an increase in productivity. Therefore predicting the population-level consequences of phenological changes requires further research to understand both the mechanisms driving seasonal variation in timing of breeding and its success.

Nightjar populations have increased in recent years, but some declines have been noted at sites supporting nationally important breeding populations. BTO research is using tracking technology to better understand the habitat requirements of this cryptic yet charismatic species, so that habitat can be optimally managed to conserve them. Population changes Although the British Nightjar population is generally faring well, increasing by 36% between 1992 and 2004 (Conway et al. 2007), there have been declines at some sites supporting regionally and nationally important numbers of this species. These declines have been attributed to the lack of available breeding habitat, but other factors may also be important, including disturbance through recreational activities and suboptimal habitat management. Habitat requirements During the breeding season, nesting habitat typically includes heathland and young conifer plantation. As both these habitats are dynamic, they require appropriate management to either maintain suitability for Nightjars, or to create replacement habitat when formerly suitable areas become overgrown. This can be achieved through felling and replanting in forest systems. However, foraging habitat is also essential for Nightjars and relatively little is known about which habitat types are the most important. It is also crucial to understand how close foraging and breeding habitats have to be for Nightjar management to be effective. Ultimately, land managers need appropriate habitat management guidance to ensure that the number of Nightjars that can be supported on a particular site is maximised, particularly where numbers have decreased. Use of technology It is difficult to observe nocturnal Nightjar activity, especially as birds may rapidly move substantial distances. A newly-published BTO study used VHF radio tracking devices to overcome this, following 31 individuals in Thetford Forest, East Anglia during 2009 and 2010 (Sharps et al. 2015). The results showed that conifer plantations aged 5-10 years were an important component of all territories, while newly planted forest (0-4 years) and grazed grassland were also used by Nightjars; all potentially important for foraging. Nightjars travelled a mean maximum distance of 747 m between breeding and feeding locations each night, demonstrating the importance of having foraging and nesting habitats in close proximity. Future research Following rapid advances in technology, GPS devices are now available, which can collect substantial quantities of high precision data. In 2014, 15 breeding Nightjars were successfully tracked with GPS in Thetford Forest and at Dersingham Bog National Nature Reserve, providing an objective and highly detailed insight into their movements. Initial analyses indicate that rapid foraging flights, often exceeding 3 km, are undertaken at dusk and dawn, to reach discrete locations that are re-visited on subsequent nights. During 2015, these apparent foraging hot spots will be further investigated with visits to observe actual Nightjar activity and examine prey abundance. Understanding the importance of these primary feeding locations and how they are used, will provide further improvements to landscape management operations and great benefits to Nightjar conservation.

Within an avian breeding population, there can be considerable variation in egg and nest site characteristics that have implications for individual reproductive success. Here we present a detailed case study of Lesser Black-backed Gulls Larus fuscus nesting on Flat Holm island, Wales, at a time when the colony was growing. This species is ground-nesting, with a modal clutch size of three. We surveyed 714 nests across the island during two consecutive years and recorded data on nest and egg characteristics, along with hatching success. We modelled how hatching success was associated with clutch size, egg volume, egg laying order and local habitat features, i.e. the amount of vegetation surrounding the nest and each nest's proximity to neighbouring nests. Eggs were most likely to hatch when they were laid in the middle of the season, were large in size, part of big clutches and in nests with a substantial amount of surrounding vegetation. Lesser Black-backed Gull productivity is currently low in many protected rural and coastal colonies throughout this species' range. Detailed information on factors influencing reproductive success could therefore indicate ways in which this species could be better managed to help maintain and conserve breeding populations. Within an avian breeding population, there can be considerable variation in egg and nest site characteristics that have implications for individual reproductive success. Here we present a detailed case study of Lesser Black-backed Gulls Larus fuscus nesting on Flat Holm island, Wales, at a time when the colony was growing. This species is ground-nesting, with a modal clutch size of three. We surveyed 714 nests across the island during two consecutive years and recorded data on nest and egg characteristics, along with hatching success. We modelled how hatching success was associated with clutch size, egg volume, egg laying order and local habitat features, i.e. the amount of vegetation surrounding the nest and each nest's proximity to neighbouring nests. Eggs were most likely to hatch when they were laid in the middle of the season, were large in size, part of big clutches and in nests with a substantial amount of surrounding vegetation. Lesser Black-backed Gull productivity is currently low in many protected rural and coastal colonies throughout this species' range. Detailed information on factors influencing reproductive success could therefore indicate ways in which this species could be better managed to help maintain and conserve breeding populations.

A long-term monitoring study involving bird ringers from five countries has investigated how changes in the reproductive output of seven species of migrant warbler vary with latitude and spring temperature. The implications for predicted changes in species distribution are also discussed.

The nominate subspecies of Eurasian Oystercatchers Haematopus ostralegus ostralegus is the most abundant of all oystercatchers and the best studied. The main breeding and wintering areas are centered on the North Sea, but the distribution covers the European Atlantic coast to as far south as Ghana in western Africa. Population size increased strongly from the 1960s to 1990s to over one million birds. Although part of this expansion may have been caused by an ongoing successful adaptation to breeding inland, the main driving forces behind this increase are not well understood. Subsequently, the population size decreased substantially by about 200,000 individuals, mainly due to strong decreases in the Dutch-German-Danish Wadden Sea area. The decrease in the Netherlands is attributed largely to overexploitation by mechanical shell-fisheries; additional factors such as agricultural intensification and reduced eutrophication are likely to also have contributed. The causes for the decreases in Germany and Denmark are less well understood and urgently require further study. In other areas numbers are fairly stable or increasing, but good data for the Nordic countries are lacking. The global (and national) conservation status of H. o. ostralegus is classified as of ‘Least Concern’. We discuss other threats, such as habitat loss, climate change, hunting and human disturbance, and make prioritized recommendations for research and management.