Citation
Overview
The populations of many migrant birds have been in decline for decades, prompting research to understand the nature of these declines so that they can be addressed. The highly complex annual cycles of migrant birds, with their long migration routes and a dependence on different sites at different times of the year, makes it very difficult to identify the drivers of decline and to implement conservation action. While our knowledge is still incomplete, can we afford to wait until we have all of the answers?
In more detail
We dedicate this review to Japheth Roberts, a brilliant young biologist from Ghana whose life was tragically cut short by illness. He made a major contribution to RSPB and Ghana Wildlife Society work in Africa – an area of work we highlight as a key ongoing priority. The review drew on discussion and insights generated at a workshop in Cambridge in 2019 generously funded by the Cambridge Conservation Initiative collaborative fund CCC-05-18-003 and RSPB and co-organized by J.V. and Susana Requena. We are grateful to all attendees for their invaluable input: Guy Anderson, Phil Atkinson, Olivier Biber, Claire Bissel, Graeme Buchanan, Malcolm Burgess, Andrew Callendar, Carles Carboneras, Nonie Coulthard, Nicola Crockford, João L. Guilherme, Jenny Gill, Borja Heredia, Vicky Jones, Felix Leichti, Alex Ngari, Abdoulaye N'Diaye, Will Peach, Rob Robinson, Tilman Schneider, Fernando Spina, David Stroud, Simon Wotton. We also thank the Editor Richard Fuller and Associate Editor Inês Catry and two anonymous referees for comments that greatly improved this review.
Abstract
The global long-term decline of migrant birds represents an important and challenging issue for conservation scientists and practitioners. This review draws together recent research directed at the Afro-Palaearctic flyway and considers its implications for conservation. The greatest advances in knowledge have been made in the field of tracking. These studies reveal many species to be highly dispersed in the non-breeding season, suggesting that site-level conservation at a small number of locations will almost certainly be of limited value for most species. Instead, widespread but ‘shallow’ land-sharing solutions are likely to be more effective but, because any local changes in Africa will affect many European populations, any impact will be extremely difficult to detect through monitoring in the breeding grounds. Targeted action to boost productivity in Europe may help to halt declines of some species but reversing declines for many species is also likely to require these ‘shallow’ land-sharing approaches in non-breeding areas. The retention or planting of native trees in the humid and arid zones within Africa may be a generic conservation tool, especially if planting is concentrated on favoured tree species. Overall, and despite a growing knowledge, we remain largely unable to progress beyond general flyway-level actions, such as maintaining suitable habitat across an increasingly anthropogenic landscape for generalists, targeted site-based conservation for specialists and at stop-over sites, protection of species from hunting, and individual species-level solutions. We remain unable to assess the cost-effectiveness of more specific conservation action, mainly because of uncertainty around how migrant populations are affected by conditions during passage and on the non-breeding grounds, as well as around the efficacy of implementation of actions, particularly in non-breeding areas. For advances in knowledge to develop and implement effective conservation, scientific approaches need to be better integrated with each other and implemented across the full annual cycle. However, we urge the immediate use of available scientific knowledge rather than waiting for a complete understanding, and that any action is combined with species monitoring and adaptive management across the flyway.
