Crested Tit population status

Estimate Crested Tit population density while accounting for imperfect detection, and assess how environmental and habitat factors influence detectability and density.

A Crested Tit perched on a lichen covered branch.

Overview

The population status of Crested Tits in Scotland is poorly known. This project will make use of recent survey data to produce updated estimates of population size and change since the 1990s. 

Project type: MSc analytical
Contact: Nick Wilkinson: nick.wilkinson@rspb.org.uk 
Closing date: Until position is filled ​​​​​​​
Timescale: 4 to 6 months ​​​​​​​
Location: Remote/desk-based project
Resources available: Data

Background

The Crested Tit is a charismatic songbird of conifer and mixed woodlands. Although widespread across much of Europe, Crested Tits in the UK are restricted to the pinewoods of northern Scotland.  

The best estimate of population size dates from a survey in the mid-1990s and is consequently out of date. The species’ limited range means that it is too scarce to be monitored by the annual Breeding Bird Survey.  

Increases in distribution recorded by the 2007–11 Bird Atlas may in part be due to improved observer effort. More recent data on Crested Tit numbers were collected during the last two national Capercaillie surveys. However, these surveys used a stratification for Capercaillie and sampled only part of the Crested Tit’s distribution.  

Using these survey data, the project will calculate updated estimates of Crested Tit density and abundance within the area of overlap and explore the potential for deriving range-wide estimates of population size. 

Methods and aims:

Using datasets of Crested Tit counts recorded on line transect surveys during the winters of 2015/16 and 2021/22, together with multicovariate distance sampling analyses, the student will calculate estimates of density accounting for incomplete detection. Analyses will explore environmental and habitat covariates of detectability and density.  

GIS layers will be used to calculate the area and composition of woodlands within the Crested Tit’s distribution and that sampled during the 2015/16 and 2021/22 surveys. Estimates of abundance will be adjusted to account for incomplete counts of group sizes.