Assessment of simple survey methods to determine breeding population size and productivity of a plover, the Northern Lapwing Vanellus vanellus
141 – 152
1 December 11
Mark Bolton, Roy Bamford, Camilla Blackburn, John Cromarty, Sarah Eglington, Norman Ratcliffe, Fiona Sharpe, Andrew Stanbury, Jennifer Smart
Royal Society for the Protection of Birds, UK Headquarters, The Lodge, Sandy, Beds SG19 2DL, UK.
Assessment of population size and annual breeding performance are key aspects of breeding wader research. There is however, often a trade-off between collecting highly reliable estimates of nest and chick survival at a small number of sites or less intensive monitoring of a larger number of sites giving less reliable estimates, but capturing more information about large-scale patterns of variation. This trade-off is often constrained by the field methods available. Here, we examine how well the population size and breeding performance of the Northern Lapwing Vanellus vanellus can be assessed from simple surveys designed to minimise fieldwork investment at the site-level compared with intensive monitoring of nest and chick survival. In addition, we use a simulation model to assess which counts are likely to provide the best predictors for hatching and breeding success and then test the efficacy of these predictions against our field data. Population size estimated from survey visits before the end of May provided very reliable measures of population size, although early morning counts tended to overestimate the number of breeding pairs. The simulation model showed that counts of recently hatched chicks should be the best predictor of hatching success but recently hatched chicks were severely under-counted in field conditions. In contrast, field counts of adults with young can provide a crude indication of hatching success. The simulation model also showed that counts of large chicks should be the best predictor of breeding success and this was supported by field data. Breeding success estimates based on the summed count of all well-grown and fledged chicks across all visits provided a reliable estimate of breeding success. The Northern Lapwing is a species of conservation concern across Europe. The use of simple survey methods to obtain reliable measures of population size and productivity represents a valuable research tool to investigate measures to improve breeding performance, and which may be adapted for use on other wader species.