Spatial and temporal variation in population trends in a long-distance migratory bird

Authors: Morrison, Catriona A.; Robinson, Robert A.1; Clark, Jacquie A.1; Gill, Jennifer A.2

Source: Diversity & Distributions, Volume 16, Number 4, July 2010 , pp. 620-627(8)

Publisher: Wiley-Blackwell

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Abstract:

Abstract Aim 

Over the past three decades, evidence has been growing that many Afro-Palaearctic migratory bird populations have suffered sustained and severe declines. As causes of these declines exist across both the breeding and non-breeding season, identifying potential drivers of population change is complex. In order to explore the roles of changes in regional and local environmental conditions on population change, we examine spatial and temporal variation in population trajectories of one of Europe’s most abundant Afro-Palaearctic summer migrants, the willow warbler, Phylloscopus trochilus. Location 

Britain and Ireland. Methods 

We use national survey data from Britain and Ireland (BBS: BTO/RSPB/JNCC Breeding Bird Survey and CBS: BWI/NPWS/Heritage Council Countryside Breeding Survey) from 1994 to 2006 to model the spatial and temporal variation in willow warbler population trends. Results 

Across Britain and Ireland, population trends follow a gradient from sharp declines in the south and east of England to shallow declines and/or slight increases in parts of north and west England, across Scotland and Ireland. Decreasing the spatial scale of analysis reveals variation in both the rate and spatial extent of population change within central England and the majority of Scotland. The rates of population change also vary temporally; declines in the south of England are shallower now than at the start of the time series, whereas populations further north in Britain have undergone periods of increase and decline. Main conclusion 

These patterns suggest that regional-scale drivers, such as changing climatic conditions, and local-scale processes, such as habitat change, are interacting to produce spatially variable population trends. We discuss the potential mechanisms underlying these interactions and the challenges in addressing such changes at scales relevant to migratory species.

Keywords: Habitat change; migratory connectivity; population dynamics; sub-Saharan Africa; willow warbler

Document Type: Research Article

DOI: http://dx.doi.org/10.1111/j.1472-4642.2010.00663.x

Affiliations: 1: British Trust for Ornithology, The Nunnery, Thetford IP24 2PU, UK 2: School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK

Publication date: July 1, 2010

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