Does variation in demographic parameters account for regional variation in Northern Lapwing Vanellus vanellus population declines across Great Britain?

Abstract

Capsule Variations in regional nest survival rates, natal philopatry, first-year and adult survival cannot explain regional Northern Lapwing population declines. Aims To assess whether regional nest survival rates, natal dispersal, and first-year and adult survival rates could explain regional variations in population declines. Methods Nest monitoring data from the period 1962–2003 were analysed to see if any differences in nest failure rates existed among regions. Estimates of nesting success were used in conjunction with aspects of Lapwing dispersal extracted from ring recovery data, to identify regional source and sink populations. Ring recovery data were also analysed to see if variation in regional population declines could be explained by variation in first-year and/or adult Lapwing survival rates. Results There was no evidence to indicate the existence of source–sink dynamics at the regional level. Nest failure rates have increased since the 1960s, and nest failure rates were highest in grassland habitats. Nest failure rates did vary among regions and regional increases in nest failure rates were associated with an increasing proportion of birds nesting on grassland habitats. There was no association between regional nest failure rates or adult and first-year survival rates and regional population declines. Conclusions Although recent increases in nest failure rates may have influenced British population declines, it is not possible to explain variation in population decline among regions through source–sink dynamics, nest failure rates or adult/first-year survival rates. It is more likely that chick mortality is the main determinant of poor Lapwing productivity and population decline.