Song thrush population dynamics
Identify the key demographic drivers of population change and determine which environmental factors best explain demographic variation.
Overview
Song Thrushes have undergone large declines on UK farmland but the causes are largely unknown. This project will utilise a rich demographic dataset (nest records, ring resightings, breeding surveys) collected from stable and declining populations to understand the drivers of decline.
Contact: Will Peach: will.peach@rspb.org.uk
Closing date: 30th June 2027
Timescale: Flexible
Location: Remote/desk-based project
Resources available: Data
Background
The UK population of Song Thrushes declined by approximately 60% between 1975 and 1995. Analyses of national demographic data have suggested the decline may have been driven by mortality at the post-fledging and adult stages (Robinson et al. 2014, Methods in Ecology and Evolution).
There is uncertainty as to the importance of the number of nesting attempts and the environmental drivers of decline.
During the period 1995–2000 the RSPB undertook a detailed comparative demographic field study of Song Thrushes in two contrasting populations. One on mixed farmland in Sussex was stable and the other on arable farmland in Essex was rapidly declining. In both study areas standardised methods were employed to measure nesting success, the number of nesting attempts and post fledging survival (from ring resightings).
There are also many casual resightings of colour-ringed thrushes that may allow the estimation of adult and first-year survival. Various covariate data are available that might explain spatial and temporal demographic variation including chick biometrics and diet, local habitat composition and quality, predator abundance and local weather.
Methods and aims
This rich dataset has never been fully analysed and has the potential to provide detailed demographic insights into the effects of land use intensity on a widespread declining species. The main research questions are:
- What are the main demographic drivers of population change?
- Which environmental factors best explain demographic variation?
The data may be suitable for the application of Bayesian Integrated Population Models (IPMs) as proposed by Kery and Schaub (Bayesian Population Analysis using WinBUGS, 2012).
Preliminary analyses suggest thrushes in the declining population made fewer nesting attempts (an aspect of demography not measured by national schemes) and consequently had lower productivity than the stable population. We expect the data are strong enough to support a publication in a peer-reviewed international journal.