Publications

Publications

BTO create and publish a variety of important articles, papers, journals and other publications, independently and with our partners, for organisations, government and the private sector. Some of our publications (books, guides and atlases) are also available to buy in our online shop.

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Changing migration patterns of the Short-eared Owl Asio flammeus in Europe: an analysis of ringing recoveries

Author: Calladine, J., du Feu, C. & du Feu, R.

Published: 2012

Analyses of almost 500 ringing recoveries spanning nearly a century show marked spatial and temporal differences in the migration patterns of Short-eared Owls (Asio flammeus) in Europe. Despite several spectacular sightings in recent months, this species is a candidate for red-listing (based on marked range contractions apparent from the Atlas). Short-eared Owls are known to show considerable annual variation in their “irruptive” migration. However this study has found that the distances travelled increased from the 1920s through to the 1960s and 1970s, but have since fallen. This provides circumstantial evidence about likely population changes (earlier studies by the BTO have shown the problems in trying to survey this species); it is speculated that the increase in migration distance was associated with population growth in the early to mid-20th century, and similarly, that populations have declined since the 1970s. Ringing recoveries also showed that birds hatching or breeding in Scandinavia and Central Europe travelled the furthest on migration, while those from Britain and the low-lying North Sea area made the shortest journeys. A reduced tendency to migrate the greater distances in the latter part of the 20th Century may have contributed to breeding declines in more southern and isolated parts of these birds’ range, where populations could have been compromised without periodic immigration. However, shorter distances between breeding and wintering grounds, especially within Britain and some British island groups, could also be particularly favourable in facilitating the conservation of this vulnerable and globally declining species: management plans are often simpler when targeted at smaller spatial scales.

01.01.12

Papers

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The importance of altitude and aspect for breeding Whinchat Saxicola rubetra in the uplands: Limitations of the uplands as a refuge for a declining, formerly widespread species?

Author: Calladine, J. & Bray, J.

Published: 2012

Like several species, the Whinchat Saxicola rubetra, was once common across lowland Europe, but has suffered substantial declines in recent decades as agricultural practices have intensified. Populations are now increasingly concentrated in more upland areas, where agriculture is of a lower intensity, but where environmental constraints, such as low ambient temperatures, may limit habitat suitability. Recent research by BTO Scotland shows that Whinchats in British uplands favour warm south- and east- facing breeding sites, which can support birds at higher altitudes than cooler north- and west-facing sites. Territory size also increased with altitude, which, along with a reduced likelihood of Whinchats being found on higher ground, provides further evidence of the constraints these birds experience at altitude. As uplands represent a refuge for a number of declining bird species, the management of the hill margins has important conservation implications. Consideration of aspect and altitude in targeted habitat management could therefore help to optimize the breeding sites available for vulnerable species.

01.01.12

Papers Bird Study

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