title: Population decline is linked to migration route in the Common Cuckoo.
abstract: Migratory species are in rapid decline globally. Although most mortality in long-distance migrant birds is thought to occur during migration, evidence of conditions on migration affecting breeding population sizes has been completely lacking. We addressed this by tracking 42 male Common Cuckoos from the rapidly declining UK population during 56 autumn migrations in 2011-14. Uniquely, the birds use two distinct routes to reach the same wintering grounds, allowing assessment of survival during migration independently of origin and destination. Mortality up to completion of the Sahara crossing (the major ecological barrier encountered in both routes) is higher for birds using the shorter route. The proportion of birds using this route strongly correlates with population decline across nine local breeding populations. Knowledge of variability in migratory behaviour and performance linked to robust population change data may therefore be necessary to understand population declines of migratory species and efficiently target conservation resources.
authors.affiliation: British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU, UK.
authors.forename: Chris M
authors.initials: CM
authors.lastname: Hewson
authors.affiliation: Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, Universitetsparken 15, 2100 København Ø, Denmark.
authors.forename: Kasper
authors.initials: K
authors.lastname: Thorup
authors.affiliation: British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU, UK.
authors.forename: James W
authors.initials: JW
authors.lastname: Pearce-Higgins
authors.affiliation: British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU, UK.
authors.forename: Philip W
authors.initials: PW
authors.lastname: Atkinson
mesh_terms: D000352:Africa, Northern; D025041:Animal Migration; D000818:Animals; D001717:Birds / Q000502:physiology*; D001947:Breeding / Q000706:statistics & numerical data; D003247:Conservation of Natural Resources; D003889:Desert Climate / Q000009:adverse effects*; D040362:Geographic Information Systems; D008297:Male; D011157:Population Dynamics / Q000706:statistics & numerical data*; D013997:Time Factors; D006113:United Kingdom