Determining the boundaries of migratory bird flyways: a Bayesian model for Eurasian teal Anas crecca in western Europe

Abstract

Accurate flyway delineation is a prerequisite for effective conservation and management of migratory bird populations, yet such limits have so far mostly been set subjectively. We present a statistical method to infer population boundaries from the analysis of ring recoveries, using a Bayesian framework. The approach was applied to Eurasian teal Anas crecca ringed in Camargue, southern France, and Abberton Reservoir, Essex, eastern England. The results presented show the boundaries of the two teal flyways in western Europe, with a zone of overlap, broadly matching those previously defined. The percentage of teal switching flyways (abmigration rate) was 2.4–2.6%, greater in birds ringed as juveniles than as adults. Abmigrants ended up at sites within the other flyway where the density of local birds was lower than expected by chance, suggesting abmigration resulted from exploratory or aberrant behaviour. The methodology presented here can be used to infer flyway boundaries of any bird with an adequate ring‐re‐encounter dataset, which has crucial consequences for the evaluation of their trends in abundance and hence conservation status, and the management of sustainable harvests.

Annual cycle of White-winged Scoters (Melanitta fusca) in eastern North America: migratory phenology, population delineation, and connectivity

“…Population delineation and migratory connectivity for species of waterfowl have usually relied on band recovery data (Madsen et al 2014;Guillemain et al 2017), genetic markers (Fleskes et al 2010;Liu et al 2012), stable isotopes (Mehl et al 2005;Swoboda 2007;Caizergues et al 2016), or some combination thereof (Pearce et al 2008(Pearce et al , 2014. Assessing stable isotopes or genetic markers, such as nuclear or mitochondrial DNA, can reliably identify overlap in population units and estimate gene flow between discrete breeding locations (Mehl et al 2005;Sonsthagen et al 2009).…”

Climate‐change not only threatens bird populations but also challenges our ability to monitor them

“…Boyd , Atkinson‐Willes , Boere & Stroud , Guillemain et al . ). Such monitoring data have formed the fundamental basis for site safeguard programmes (such as designation of Ramsar sites under the 1% criterion and Special Protection Areas under the European Union Birds Directive), which have made a vital contribution to protecting these populations and maintaining their generally favourable conservation status.…”

Spring migratory routes and stopover duration of satellite‐tracked Eurasian Teals Anas crecca wintering in Italy

“…Although the migratory course and destinations of the species are quite well known thanks to the large number of ringing recoveries (Guillemain & Elmberg , Guillemain et al . ), the present results add valuable information on several aspects of migration strategies such as timing, speed of travel and stopover length. As birds were tagged in three sites characterized by different management policies and two of them (TUS and VEN) are within areas hosting a Teal wintering population of national importance (Zenatello et al .…”

“…In the western Palaearctic, Teal migration has been studied with ring‐recoveries (Wolff , Guillemain & Elmberg , Guillemain et al . ) and only a few birds have been tracked by satellite, mostly in central East‐Asia (Gaidet et al . , Takekawa et al .…”