ABSTRACT Capsule Slavonian Grebes Podiceps auritus breeding in Iceland moult on freshwater, before migrating to the seas around the British Isles for the winter. Aims The aims were to describe the migration strategies and identify wintering areas of Slavonian Grebes breeding in Iceland. Methods Geolocators were fitted to 37 Slavonian Grebes breeding on two lakes in north-east Iceland from 2009 to 2012. Of these, 19 were recovered and provided useful data on wintering areas and migration timing. Results The results indicated that the grebes moulted on freshwater lakes before gradually moving to the sea and later migrating to the wintering areas. Most of the birds wintered on the sea around the British Isles. However, there was surprisingly high variation in wintering strategies and little overlap of wintering areas. Grebes tracked for consecutive years showed high wintering philopatry. Conclusion Individual Slavonian Grebes may be vulnerable to local environmental conditions, but the high variability in wintering strategies and relatively large non-breeding distribution is expected to make the population generally less sensitive to local environmental conditions in the wintering areas over the long term.

ABSTRACT Capsule The first UK European Turtle Dove Streptopelia turtur survey, in 2021, estimated the breeding population at 2092 territories. Aims Changes in European Turtle Dove abundance in the UK have been monitored through schemes like the BTO/JNCC/RSPB Breeding Bird Survey, however, sample size is now too low to calculate robust trends going forward. The aims of this volunteer-based survey were to provide a new UK population estimate and create a baseline to monitor future population trends. Methods A stratified random sample of one-kilometre squares were surveyed within the core counties for the species. Elsewhere, one-kilometre squares containing recent European Turtle Dove records were targeted. The survey used a two-visit territory mapping approach, with observers asked to get within 200 metres of potentially suitable nesting or foraging habitat. Visits were undertaken in the early morning, to coincide with peak vocal activity, from 11 May to 31 July. Results The UK population estimate in 2021 was 2092 territories (95% confidence limits, 1559–2782). The species has become increasingly restricted to eastern and southeastern England, with 62.5% of the population estimated to occur in three counties: Kent (682 territories; 32.6%), Suffolk (326; 15.6%) and Essex (300; 14.3%). Additional hotspots occurred in other counties in eastern England, up to North Yorkshire. Conclusion This result suggests a 98% decline in abundance since the 1968–1972 breeding atlas, similar to trends identified from UK bird monitoring schemes, and a substantial contraction in range since the 2007–2011 bird atlas. The temporary cessation of hunting along their European western flyway provides a vital window of opportunity to scale up the delivery of high-quality breeding habitat and increase food availability in the UK. The survey should be repeated in 2026, and regularly thereafter, to help monitor the effectiveness of conservation interventions.

ABSTRACT Capsule Dead Sea Sparrows Passer moabiticus transferred their historical breeding colony location, following geo-ecological and hydrological changes, to a new, less arid zone within a nature reserve. Aims To find biotic and abiotic factors affecting the choice of nest sites by Dead Sea Sparrows, in order to locate potential breeding areas and plan in advance for their protection. Methods Mapping old and new nest sites of Dead Sea Sparrows within Einot Tzukim nature reserve, Dead Sea Valley, and using anthropogenic and geo-ecological GIS layers, we created a map of the potential preferred breeding colony area. Results We found the biotic and abiotic factors affecting nest site preference of Dead Sea Sparrows, which included areas far from human activity, areas close to historic springs, and areas affected by a major fire. New areas in the reserve exposed by the retreating Dead Sea were inhabited by the birds, which gradually transferred their breeding centre to a less arid zone within the reserve. Conclusion When managing colonial breeding sites, it is crucial to understand the role of both natural and anthropogenic influences in order to prioritize sites for conservation and management. Producing a preference map, based on such data, can help managers locate potential breeding areas and plan in advance for their protection.

ABSTRACT Food stealing from humans by Herring Gulls Larus argentatus increased with human food availability but was not associated with any food preferences. Gulls obtained significantly more food when stealing than when scrounging, and the response of most people was neutral, suggesting that food stealing is a low-risk, high-reward strategy for urban Herring Gulls.

ABSTRACT Capsule Migration studies of tagged Eurasian Bitterns Botaurus stellaris provide information on the behaviour of this secretive species in relation to weather conditions. Aims To study if cold spells trigger southward migration in resident Eurasian Bitterns. To describe migratory behaviour including flight routes, altitudes, flight direction in relation to wind speed and direction, and general characteristics of stopping sites. Methods Six adult Eurasian Bitterns from Dutch breeding areas were followed for two to five years using ARGOS-PTT/GPS transmitters or GPS trackers. Results Four individuals remained at the breeding sites in winter and did not migrate in response to cold spells. Two individuals covered distances of 300 and 1600 km between stopping sites. They migrated predominantly at night, but over the Sahara they extended flights into daylight hours. Depending on wind assistance, flight speeds (groundspeed) varied between 3.6 and 26 ms−1. Flight altitude varied from just above sea level when facing headwinds, to almost 2000 m above sea level under tail wind conditions. Repeatedly tracked individuals showed substantial variation in routes and stopping sites between successive migrations. These flight patterns appeared influenced by the speed and direction of the winds encountered en route. Conclusions Eurasian Bitterns were either migratory or resident and the latter individuals did not perform facultative movements at the onset of cold spells. The flight speed, flight altitudes, and routes of migrating birds were influenced by wind conditions. This likely explains the variable use of stopping sites between years.

ABSTRACT Capsule Small rodents and amphibians are both important prey items for the Lesser Spotted Eagle Clanga pomarina, and their proportions in the diet depend on their local availability, as well as the degree of involvement of the female in food provisioning to the nestlings, which increases towards the end of the breeding season. Aims To describe the diet composition and aspects of the food supply of the Lesser Spotted Eagle during the nesting period. Methods Cameras were installed at five nests of three pairs of the Lesser Spotted Eagle in eastern Latvia, to collect data on food items brought to the nests. Results Of 3109 identified prey items, small rodents (43.36%) and amphibians (44.81%) were the most important prey groups. The proportion of common (small rodents and amphibians) and uncommon (moles, birds and others) food items differed between nests and years. Among the common food items, the deficiency of small rodents in some years was compensated for by an increase in frogs and vice versa. Male eagles brought 66% of all food items to the nest. Females brought more amphibians and fewer rodents than did males. After hatching, the mean number of food items delivered to the nest was 6.9 per day. The main activity period of food delivery was between the 3rd to 7th hour after sunrise. Conclusion The alternative prey hypothesis explains the diet of the Lesser Spotted Eagle in our study area. Rodents and amphibians are food items of equal importance that can replace each other, depending on their availability. The increasing share of amphibians towards the end of the breeding season was mainly a result of an increasing proportion of prey items brought into the nest by females.

ABSTRACT Capsule COVID-19 restrictions significantly biased BTO/JNCC/RSPB Breeding Bird Survey coverage across the UK allowing indicative trends to be produced for approximately one-third of species in England only. Aims To investigate the effect that COVID-19 restrictions had on participation in and coverage of the Breeding Bird Survey (BBS), and to quantify the likely impacts on population change reporting based on 2020 data. Methods We determined geographic, seasonal, and habitat coverage for the BBS in 2020 and compared this to previous years, and quantified the scale of biases and reductions in sample size for target species. We degraded existing BBS data (1994–2019) to simulate 2020 coverage and produced population change estimates using three methods applied to the complete and degraded data to assess the impacts of 2020 coverage on emergent trends. Results In 2020, 49% fewer survey squares were visited compared to 2019. Reductions were greatest in Wales, Scotland, and Northern Ireland, and in the early breeding season, when 90% fewer visits were made. The few early visits completed were on atypical dates and showed marked habitat biases. Individual species were detected in 23–96% fewer squares than normal. Population change estimates derived using routine trend models were negatively biased in up to 96% of species, with errors greatest for species normally detected on early visits. Alternative trend models using visit-specific parameterization or focussing only on late season visits overcame coverage biases for some species. Conclusions Lockdown restrictions associated with the COVID-19 outbreak meant it was not possible to produce population trend information for UK, Wales, Scotland, or Northern Ireland in 2020. Indicative long-term trends could be produced in England only for a subset of about 40 species. We recommend managers of citizen science schemes undertake similar analyses to assess the scale of coverage biases when unforeseen events cause temporary, but substantial changes, in sampling effort.

ABSTRACT Capsule European Starlings Sturnus vulgaris nested mostly in natural holes with strong walls (in live trees), typically excavated by medium-sized woodpeckers (small entrances, deep cavities), and high above the ground. Co-occurrence of these safety-enhancing features suggests that predation avoidance has been the main force shaping patterns of Starling nest site selection. Aims To describe patterns of nest site use by Starlings in a primeval forest and to assess the adaptive value of nest site choice. Methods Observations were made of Starlings breeding in undisturbed conditions in a strictly protected part of the Białowieża National Park, Poland. Intensive searches were made for nests (n = 2039) in permanent observation plots during 46 breeding seasons (1975–2020), coupled with measurements of hole attributes and observations of fate and re-use of nest sites. Results Starlings bred along forest edges in holes located in several species of deciduous tree; tree species used differed among habitats and hole location differed across tree species. The birds bred mostly in holes excavated by woodpeckers (70.3%), in trunks (77.4%) of living trees (84.5%). The median girth at breast height of these trees amounted to approximately 170 cm and median height of holes above the ground was 13 m. Starlings used holes excavated by the medium-sized woodpeckers roughly in proportion to their availability in the forest (tree species, stature, height above the ground). About 39% of holes were re-used in the consecutive years, with some holes being used over several decades. Conclusion The features of Starling nest holes (strong walls, narrow entrances, deep cavities) probably constitute adaptations to the need to evade predators. Their body size allows them to nest in excavated holes without threat of their broods being destroyed by woodpeckers.

ABSTRACT Capsule Great Cormorants Phalacrocorax carbo sinensis use vocal communication during the breeding season, with males being particularly vocal earlier in the breeding cycle and showing individual variation in some calls, which could be used for individual recognition. Aims To identify and describe vocal behaviour of Great Cormorants, to link calls with observed behaviours and to explore if the calls had potential for individual recognition. Methods We followed 21 nesting pairs of Great Cormorants by videoing and recording their vocal behaviour throughout the breeding season. We linked calls with observed behaviours, and measured the acoustic characteristics of the calls using signal analysis tools in Matlab. Results We identified and measured acoustic characteristics of six different call types: courtship, landing, nest building, nest relief, jumping, and chick begging calls. Five of these call types were linked to distinctive breeding behaviours. Vocal signalling occurred between the male and female, and between parents and offspring. Males showed higher vocal activity than females and used a larger repertoire of calls. The courtship call was the most common call type in both sexes. These calls also differed acoustically between the sexes; male calls were longer in duration than female calls (617 ms versus 323 ms) and had wider bandwidth (763 Hz versus 473 Hz). Conclusion Great Cormorants use vocal communication for social interactions. Males were vocally more active and had a larger repertoire of calls than females, and calls differed between the sexes. Calls of males also differed individually and could, therefore, function for individual recognition in this species.

ABSTRACT Capsule Our multi-scale habitat selection and spatial analysis of a threatened population of Taiga Bean Geese Anser fabalis highlights the importance of monitoring and review programmes to determine whether species conservation measures are being implemented at the correct spatio-temporal scales. Aims To undertake a habitat selection and spatial analysis of an internationally important population of Taiga Bean Geese, and quantify the extent to which their foraging range overlaps with a protected area classified to protect their roost sites and foraging areas. Methods A five-year field count dataset was used to quantify foraging habitat selection at the population range scale. In addition, global positioning system (GPS)/ultra high frequency loggers were attached to 12 birds and GPS location data were collected to quantify foraging habitat selection at an individual foraging range scale. Results Generalized linear models predicted that, at the population foraging range scale, Taiga Bean Geese selected agriculturally improved pasture, and this selection was more pronounced at greater distances from public roads. At an individual foraging range scale, compositional analysis revealed that agriculturally improved pasture was significantly selected over all other habitats. There was a substantial mismatch between their individual foraging ranges and the protected area, with less than 35% (median: 21%; range 9.5–31.9%) of their individual full foraging ranges overlapping with the protected area. Discussion Fixed protected areas may fail to fully accommodate the spatio-temporal foraging dynamics of geese, however a more appropriate conservation measure may be the use of flexible management schemes to maintain their foraging areas within and beyond protected area boundaries. This case study highlights the importance of developing dynamic conservation strategies for species liable to undergo range shifts.