Spatial variation in spring arrival patterns of Afro-Palearctic bird migration across Europe

The timing of migrant birds’ arrival on the breeding grounds, or spring arrival, can affect their survival and breeding success. The optimal time for spring arrival involves trade-offs between various factors, including the availability of food and suitable breeding habitat, and the risks of severe weather. Due to climate change, the timing of spring emergence has advanced for many plants and insects which affects the timing of maximum food availability for migratory birds in turn. The degree to which different bird species can adapt to this varies. Understanding the factors that influence spring arrival in different species can help us to predict how they may respond to future changes in climate.

Birds of Conservation Concern Wales 4: the population status of birds in Wales

The latest review of the conservation status of birds in Wales. The report assessed all 220 bird species which regularly occur in Wales. There are now 60 species of bird on the Red List, with 91 on the Amber List and just 69 - less than a third of the total number of species - on the Green List.

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Demography of Common Swifts Apus apus breeding in the UK associated with local weather but not aphid abundance

Data from the BTO/JNCC/RSPB Breeding Birds Survey reveal that breeding Swift populations in the UK are in decline. Both reductions in the availability of invertebrate prey and the loss of nesting sites have been suggested as possible reasons, but the ultimate drivers of this decline are poorly understood. Can we improve our understanding of Swift decline by bringing together the information collected by bird ringers and nest recorders alongside data on insect availability and weather?

A 30,000-km journey by Apus apus pekinensis tracks arid lands between northern China and south-western Africa

The Swift is widely distributed with a cross-continental breeding range spanning Europe and large parts of Asia and north Africa. Until recently, Swift migration research has focussed on populations which breed in Europe and north-western Africa (the apus subspecies), leaving the migration of birds breeding throughout Asia (the pekinensis subspecies) shrouded in mystery.

The status of our bird populations: the fifth Birds of Conservation Concern in the United Kingdom, Channel Islands and Isle of Man and second IUCN Red List assessment of extinction risk for Great Britain

Commonly referred to as the UK Red List for birds, this is the fifth review of the status of birds in the UK, Channel Islands and Isle of Man, published in December 2021 as Birds of Conservation Concern 5 (BOCC5). This updates the last assessment in 2015. Using standardised criteria, experts from a range of bird NGOs, including BTO, assessed 245 species with breeding, passage or wintering populations in the UK and assigned each to the Red, Amber or Green Lists of conservation concern. 

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Evolution of chain migration in an aerial insectivorous bird, the Common Swift Apus apus

The highly aerial Common Swift Apus apus, which spends the non‐breeding period on the wing, has been found to exhibit a rarely‐found chain migration pattern.

Identification of putative wintering areas and ecological determinants of population dynamics of Common House-Martin Delichon urbicum and Common Swift Apus apus breeding in Northern Italy

To identify the causes of population decline in migratory birds, researchers must determine the relative influence of environmental changes on population dynamics while the birds are on breeding grounds, wintering grounds, and en route between the two. This is problematic when the wintering areas of specific populations are unknown. Here, we first identified the putative wintering areas of Common House-Martin (Delichon urbicum) and Common Swift (Apus apus) populations breeding in northern Italy as those areas, within the wintering ranges of these species, where the winter Normalized Difference Vegetation Index (NDVI), which may affect winter survival, best predicted annual variation in population indices observed in the breeding grounds in 1992–2009. In these analyses, we controlled for the potentially confounding effects of rainfall in the breeding grounds during the previous year, which may affect reproductive success; the North Atlantic Oscillation Index (NAO), which may account for climatic conditions faced by birds during migration; and the linear and squared term of year, which account for nonlinear population trends. The areas thus identified ranged from Guinea to Nigeria for the Common House-Martin, and were located in southern Ghana for the Common Swift. We then regressed annual population indices on mean NDVI values in the putative wintering areas and on the other variables, and used Bayesian model averaging (BMA) and hierarchical partitioning (HP) of variance to assess their relative contribution to population dynamics. We re-ran all the analyses using NDVI values at different spatial scales, and consistently found that our population of Common House-Martin was primarily affected by spring rainfall (43%–47.7% explained variance) and NDVI (24%–26.9%), while the Common Swift population was primarily affected by the NDVI (22.7%–34.8%). Although these results must be further validated, currently they are the only hypotheses about the wintering grounds of the Italian populations of these species, as no Common House-Martin and Common Swift ringed in Italy have been recovered in their wintering ranges.