Headstarting involves collecting eggs from wild nests, rearing the eggs and hatched chicks in captivity, then releasing chicks back into the wild when they are of fledging age. It has been successfully employed as a conservation strategy for other wader species like Black-tailed Godwit and Spoon-billed Sandpiper. Several Curlew headstarting projects are underway in lowland England, with other projects in Ireland, Belgium, Germany and Poland. But for headstarting to work as a conservation strategy for small Curlew populations, there is a key measure of success – will headstarted birds be faithful to their release site and return in sufficient numbers as breeding adults, and over what timescale? If Curlew disperse widely and recruit into other populations, or at low densities throughout the wider countryside (or even beyond), headstarting won’t meet the aim of boosting local populations. However, if over time released Curlew return to breed locally, then headstarting may prove a highly valuable emergency conservation measure for threatened populations.
It takes a long time to assess the viability of headstarting as an effective Curlew conservation tool. Curlew are long-lived birds and slow to reach breeding age. A 20 year study in the Netherlands found that of 32 identifiable Curlew ringed as chicks which returned to the study area, 19% returned in their second calendar year, 28% in their third calendar year, 28% in their fourth calendar year, and 25% in their fifth calendar year (Gerritsen 2021). With the first birds from the Norfolk project released in 2021, the project is only now at the point of being able to start to assess the recruitment of headstarted birds into the local breeding population.
Key to detecting returning headstarted birds is long-term monitoring of the local breeding population. Since 2023, project staff at the BTO have been undertaking dedicated Curlew surveys in eastern England looking for returning headstarts which are clearly identifiable by their colour-marks. With the initial expectation that returning birds would settle near their ‘natal’ site (in the case of headstarts, their release site), surveys in 2023 and 2024 focused on randomised surveys of 2 km OS grid squares around the release sites in northwest Norfolk, with proportionally greater search effort near the release sites, given the Dutch study described above found 80% of chicks returned to breed within 12 km of their natal site. However in 2025, we started including surveys at known Curlew breeding sites in Norfolk and Suffolk, the reasons for which are described below.
Not far (as the Curlew flies) from the release sites, the Brecks hosts one of the largest remaining Curlew breeding populations in lowland England, estimated at around 150 pairs according to BTO staff member Harry Ewing, who started studying this breeding population in 2019 for his PhD research with BTO and the University of East Anglia. As part of a parallel project testing interventions to boost Curlew breeding success in the Brecks and other sites in England, Harry has been undertaking intensive monitoring and nest-finding at key breeding sites around Breckland since 2023. In 2024, the first headstarted Curlew were found at several of these sites, with three individuals confirmed breeding (i.e. nesting confirmed) – two paired with each other, and the third paired with a wild bird. A number of other birds were seen at breeding sites that year exhibiting breeding-type behaviours. These birds may have indeed bred, or they could have been ‘prospecting’, that is dropping in to visit prospective breeding sites away from their ‘natal’ site.
This year has seen a surge in recruitment, with 12 confirmed or probable nesting attempts in eastern England, and an additional 14 birds either possibly breeding or indeed prospecting. All but one of the latter 14 birds are in Norfolk / Suffolk, with a lone individual found attempting breeding in Staffordshire. The majority of eastern England sightings have all come from known Curlew ‘hotspots’ (i.e. sites with existing pairs of breeding Curlew). No birds have been found breeding in proximity to their release sites at Wild Ken Hill and Sandringham, although a number have been seen and confirmed nesting on RAF Sculthorpe less than 10 km east of Sandringham, a site with a small number of existing wild pairs. Some birds from previous years are still wearing GPS tags, and the GPS locations have not only led us to nesting attempts, but have also shown fascinating insights into the prospecting behaviour of young Curlew as they seemingly sample breeding hotspots, often visiting more than one site in a single day.
We are only beginning to understand whether headstarting can be an effective tool for Curlew conservation. The indication from 2025 is that continued, long-term monitoring of local breeding sites will be critical to this understanding. But headstarting alone will not save breeding Curlew from continued declines or even local extirpation – it must be used in conjunction with habitat improvement and interventions that prevent losses of eggs and chicks to predators and agricultural activities. 2025 has been a hopeful year for the East of England headstarting project with birds returning to breed in greater numbers. However, it has also shone a light on the dispersal and recruitment behaviour of immature birds, which is as yet a major gap in our understanding of Curlew ecology.