DOI: 10.5061/dryad.6t1g1jx95
title: Climate, habitat and demography predict dispersal by an endangered bird in a fragmented landscape

description: Worldwide, biodiversity is threatened by human-induced habitat degradation
 and fragmentation. Dispersal, particularly long-distance dispersal between
 isolated habitat fragments, is key for population connectivity and species
 persistence in the face of environmental change. However, we lack
 understanding of how habitat fragmentation and degradation itself affect
 the dispersal process. To identify conditions that promote or constrain
 connectivity, we need to reveal how habitat, demographic, and climatic
 conditions drive dispersal success and distance. This is challenging,
 however, because detecting dispersal events in wild animals, especially
 over long distances, is notoriously difficult. Here we address this in the
 Endangered purple-crowned fairy-wren, Malurus coronatus, a small
 cooperatively breeding songbird in which individuals can opt to delay
 natal dispersal, and we are able to consistently detect dispersal by
 colour-marked individuals, including over long distances. Thus, an
 assessment of drivers of dispersal success and distance is achievable.
 Using data from a 17-year study, we analyse dispersal probability for 796
 individuals, and distance of 206 dispersal events (up to 68 km). We show
 that poorer quality and isolated habitat is associated with more frequent
 dispersal, and over greater distances. Additionally, low population
 density promotes dispersal, while higher rainfall (which increases food
 availability for several months), especially during the wet season,
 increases dispersal distance, particularly at high population density.
 This indicates that, when the population is saturated, favourable
 conditions may allow birds to successfully disperse over the long
 distances required to connect fragments. Policy implications: Our findings
 suggest that while habitat fragmentation and degradation may promote
 dispersal, such dispersal, especially over greater distances, may require
 benign climatic conditions, presumably to limit its cost. Our results
 highlight the need to integrate the impacts of climate change when
 assessing how habitat degradation and fragmentation affect population
 connectivity. Additionally, we recommend conservation management actions
 targeted at increasing source population density as an important first
 step in promoting connectivity between habitat fragments via long-distance
 dispersal.
description: # Climate, habitat and demography predict dispersal by an endangered bird
 in a fragmented landscape
 [https://doi.org/10.5061/dryad.6t1g1jx95](https://doi.org/10.5061/dryad.6t1g1jx95) ## Description of the data and file structure Long-term data on purple-crowned fairy-wren movement was collected, to analyse drivers of natal dispersal likelihood and distance. ### Files and variables #### File: Data\_Teunissen\_JPE.xlsx **Description:** This file contains the data used to analyse drivers of natal dispersal likelihood and distance in purple-crowned fairy-wrens, as presented in Teunissen et al. 2025. Climate, habitat and demography predict dispersal by an endangered bird in a fragmented landscape. Journal of Applied Ecology. The file contains two separate sheets: * "Dispersal likelihood" - Data file used to analyse the effect of habitat, climate and demography on individual purple-crowned fairy-wrens' likelihood to disperse from their natal territory to a dominant breeding position. This data consists of 2,431 observations on 796 birds over 17 years. * "Dispersal distance" - Data file used to analyse the effect of habitat, climate and demography on dispersal distance by 206 purple-crowned fairy-wren individuals that successfully dispersed to a dominant breeding position. ##### Variables * Focal bird ID: Identifier of the purple-crowned fairy-wren individual * Sex: Sex of individual (male, female) * Year: Year corresponding to observation (2006-2022) * Season: Season corresponding to observation (non-breeding, pre-breeding, breeding) * Rainfall preceding wet season (mm): Total rainfall during the preceding wet season for each season; from November to April for the breeding season, from November to May for the non-breeding and pre-breeding seasons * Population density (# birds): Number of birds present in the core study population on the last day of the season * Age (years): Age of focal bird on the last day of the season (in years) * Territory ID: Identifier of the focal bird's natal territory * Distance to nearest neighbours (km): Distance from the border of the focal bird's natal territory to the closest border of the nearest neighbouring territory (in km) * Distance to second nearest neighbours (km): Distance from the border of the focal bird's natal territory to the closest border of the second nearest neighbouring territory (in km) * Number of territories in vicinity: The number of territories within 50 m of the focal bird's natal territory border * Pandanus volume: Riparian habitat quality of focal bird's natal territory * Habitat index (PC): Principal component representing an index of habitat quality and connectivity, made up of the above four variables, with approximately equal loadings; negative for distance to nearest and second nearest neighbours and positive for number of territories in the vicinity and pandanus volume * Dispersed (0 = no, 1 = yes): Whether the focal bird dispersed (no, yes) in the given season * Dispersal distance (km): The distance dispersed by the focal individual, measured from the centre of the natal territory to the centre of the new territory, along the shortest route possible following intervening waterways