Widespread declines in breeding performance have caused the IUCN to classify the Curlew as near-threatened. The UK hosts an internationally significant overwintering population, but conservationists fear that impending habitat loss due to sea-level rise will put even greater pressure on this struggling species. Building new intertidal habitat to compensate for these losses is one viable counteraction, but in order to make effective management decisions, we must first understand how Curlew use their winter home range. In a collaborative study led by the University of Hull, BTO scientists aimed to find out more by establishing the overwinter home range size (the size of the space used by the birds during winter) of Curlew in the Humber Estuary, North-East England, UK. Curlew visit both estuarine and agricultural habitats during winter, but this study may be the first to examine how this habitat use changes throughout the non-breeding season. As Curlew display sex-differences in bill length which impact foraging technique, this study also wanted to determine if males and females used habitats differently. Over the course of four winters, GPS tags were deployed on 18 Curlew from two sites (Welwick Marsh and Long Bank Marsh) on the Humber Estuary. An in-depth analysis of these GPS data allowed the researchers to estimate the home range size of the individual birds and, for the first time in a wader species, infer their behaviour from their movement patterns. These analyses revealed where and how the Curlew were spending their time, both on a daily basis and across the season. The study uncovered a number of surprising results. The Curlews’ average home range size was 76.1 ha, which is considered small when compared to other wading species such as Knot and Dunlin. Furthermore, contrary to expectations, a slight decrease in Curlews’ home range size was detected as the winters progressed. These results imply that the high-quality habitats of the Humber Estuary had a plentiful supply of food, meaning the birds were not forced to travel long distances or expand their home ranges in response to resource depletion. Unexpectedly, although the Curlew spent more time resting at night (31% compared to 13% during the day), their nocturnal home range was often larger than their diurnal one. Home range characteristics and use also differed between individuals. For example, some birds travelled up to 3.5 km inland to forage on farmland, while others stayed exclusively on tidal mudflats. Contrary to predictions, these differences were not explained by sex. Instead, Curlew foraging behaviours varied between groups of birds wintering at different locations on the estuary. The drivers behind these individual differences remain cryptic, but it is probable that Curlew employ specialised foraging tactics to avoid competing with one another. As conservationists aim to support their survival, they should account for this variety of strategies when maintaining habitat on the Curlews’ behalf. Although these findings may be site specific, the valuable knowledge that Humber Estuary Curlew maintain relatively small home ranges and employ individualised foraging strategies will inform management responses to sea-level rise and habitat conservation. Crucially, this study also demonstrates there is still much to learn about Curlew habitat use, paving the way for future work.

Urban areas can and do hold significant populations of birds, but we know surprisingly little about how these populations are connected with those present within the wider countryside. It has been suggested that the populations using these different habitats may be linked through seasonal movements, with individuals breeding in rural areas moving into urban sites during the winter months to exploit the supplementary food provided at garden feeding stations. However, little work has been done to test this hypothesis.

Birds move a lot during their lifetime! One of the most important forms of movement is dispersal: when birds move out of the immediate area in which they were born (natal dispersal) or when they change location between successive breeding attempts (breeding dispersal). Understanding dispersal movements can provide insight into species’ distribution, gene flow and protection needs. Unfortunately, data which demonstrate how far and often birds move during dispersal is difficult to collect and analyse, and so many questions about these behaviours remain unanswered. Ringing data collected by volunteers are a potential source of information on bird dispersal, but specialist methods must be employed if they are to be analysed correctly. In a study conducted in collaboration with BTO, scientists estimated the dispersal patterns of 234 European bird species using data from the EURING (European Union for Bird Ringing) Databank of birds ringed and subsequently re-encountered (either alive or dead). Information on where ringed birds had been recaptured or found dead demonstrated how far they had travelled. The raw data were first processed in order to reduce the bias caused by an uneven ringing effort across the continent. The scientists then used these data to create a ‘dispersal kernel’ for each species. Dispersal kernels describe the number of birds moving different distances; most don’t disperse very far, but a few individuals can move a long way. A number of different methods for estimating dispersal kernels already exist, each of which has its own set of assumptions about the birds’ behaviour, and the team compared four of these to determine which was the best fit for their ringing data. They could then better quantify the bird’s behaviour based on the assumptions of the best fitting method. Being able to describe dispersal in this way makes it possible to incorporate this information into other analyses; for example, investigations into how changes in the environment might influence population change. The scientists were also able to compare dispersal characteristics between the sexes and investigate if the patterns seen were different depending on whether it was natal or breeding dispersal. The scientists found that the data for almost all of the featured species were best described by so-called ‘heavy-tailed’ kernels. This means that for most species, although most individual birds are unlikely to travel far, more individuals than might be expected undertake long-distance movements. These long-distance dispersal events can introduce new species or genes into an area, but they are very rarely detected. By developing these methods as part of this analysis, this paper may help others to make more accurate predictions of bird movements in the future. As predicted, the scientists also found that birds tended to travel further during natal dispersal than breeding dispersal. When leaving the area in which they were born, birds travelled (on average) more than twice the distance they covered when swapping breeding sites (7.74 km compared to 2.83 km). Putting some distance between yourself and your immediate family may help to avoid inbreeding or prevent direct competition with siblings.Surprisingly, the study did not find any widespread sex-biased dispersal patterns. In many bird species, it is thought that the females engage in dispersal more regularly than males; however, these patterns were not replicated in this study. In future, considering how dispersal differences between the sexes might change with age could shed some light on this discrepancy. Testing statistical methods using empirical data is crucial to appraise their accuracy and understand their limitations. The methods included in this study will help future work produce more realistic models, paving the way for scientists to address many of those unanswered questions on avian dispersal patterns. As species continue to adjust their ranges in response to climate change, this information could have considerable conservation value.

New research has revealed the wintering grounds and migration stopovers of British-breeding Wood Warbler, a declining species on the UK Birds of Conservation Concern Red List.

Monitoring biodiversity at large spatial scales and over long periods of time is central to understanding how populations change, and supports conservation planning and the prioritisation of resources by decision-makers. While we have a good understanding of the monitoring frameworks that exist for some taxa, e.g. birds, such understanding is lacking for many others, including reptiles and amphibians. This paper sets out to fill this knowledge gap for UK reptiles and amphibians, identifying existing sources of biodiversity data for these taxa and then characterising the nature of the data management network within which they sit. By using an approach known as network analysis, the team was able to visualise how the reptile and amphibian data were mobilised across the network, i.e. which were the key data sources within the network and how did data flow across the network? It also revealed valuable information on the species recorded and the degree of geographic and spatial coverage over time. Forty-five sources of amphibian and reptile data were identified, which clustered into three main groupings: ‘recording projects’, ‘recording communities’ and ‘digital data platforms’. ‘Recording projects’ involve structured or semi-structured monitoring, the typical projects operated by BTO such as the reptile and amphibian component of BTO Garden BirdWatch. The network analysis revealed that the UK amphibian and reptile monitoring portfolio is dynamic and fragmented, with two data sources sitting outside of the network and many others receiving data but not then sharing this with other sources. While the network as a whole may provide comprehensive information across species and regions, the complexity of the network and the degree of fragmentation means that opportunities to leverage information where and when it is needed are not as good as they could be. If such shortcomings can be addressed then this would benefit reptile and amphibian conservation within the UK.