Changing demography and population decline in the Common Starling Sturnus vulgaris: a multisite approach to Integrated Population Monitoring

Abstract

Understanding demography is critical for understanding the causes underlying population declines, and for initiating and monitoring policies to reverse them. A method of fitting demographic models directly to avian count data recorded at a sample of census sites is described. The model is applied to national and regional counts of Common Starling Sturnus vulgaris in Britain for the period 1965–2000. Starlings have declined markedly during this time and are now on the list of birds of highest conservation concern. Although there have been small changes in various aspects of breeding success over this time, the analysis shows that these are unlikely to have made much impact on the long‐term status of the species. By incorporating estimates of survival, based upon recoveries of ringed birds, the model suggests that the pronounced national decline in Starling numbers since a period of stability in the 1970s is most likely to be due to changes in the survival of first‐year birds. This narrows the candidate range of environmental factors which might influence the decline and implicates changes in resource availability.

An Integrated Population Model From Constant Effort Bird-Ringing Data

“…Brooks et al (2004) and King et al (2008) demonstrated how the model could be re-cast in a Bayesian framework. Freeman et al (2007) fi tted demographic population models directly to the raw counts but again fi xing the demographic parameters to previously estimated values. Besbeas and Freeman (2006) essentially combine the methods of Besbeas et al (2002) andFreeman et al (2007) thereby correctly accounting for both the correlation and sampling variance in both the demographic parameters and the derived abundance indices.…”

“…Productivity rates in integrated models have been previously estimated either as a free parameter in the population model (Besbeas, Freeman, Morgan and Catchpole, 2002;Besbeas and Freeman, 2006;King, Brooks, Mazzetta, Freeman and Morgan, 2008), or by including estimates of breeding success (at least on a per nesting attempt basis) from nest record data (Freeman, Robinson, Clark, Griffin and Adams, 2007;Reynolds et al, 2009).…”

Quantifying changes in abundance without counting animals: extensions to a method of fitting integrated population models

“…Suppose annual counts C it of a species of interest at site i , i=1, …, S, are taken in the breeding season of year t , t=1, …, T. These counts are typically modelled as independent Poisson observations with expected values μ it dependent upon two factors, the site and the year, expressed as parameters s i and y t respectively, and additive on a log scale (Besbeas and Freeman, 2006;Freeman et al, 2007b;Cave et al, 2010): (Peach et al 1999;Siriwardena et al 2001;Freeman and Crick 2003;Freeman et al 2007b;Cave et al 2010) Freeman et al 2007b):…”

Monarch Butterflies Use Regenerating Milkweeds for Reproduction in Mowed Hayfields in Northern Virginia

“…Thousands of frog populations have been decimated by the spread of amphibian chytrid fungus (Batrachochytrium dendrobatidis) since 1998 including dozens of species extinctions and precipitous declines of even widespread species (La Marca et al 2005, Skerratt et al 2007). Many species of well-known birds have undergone recent dramatic decline in agricultural areas in Europe (Vincent 2005, Freeman et al 2008). In the United States, rusty blackbirds (Euphagus carolinus) have experienced one of the most significant declines ever documented among North American birds in recent times.…”