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Supplementary feeding restructures urban bird communities
Josie A Galbraith1, Jacqueline R Beggs2, Darryl N Jones3
1Centre for Biodiversity and Biosecurity, School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand; and jgal026@aucklanduni.ac.nz.
Summary
Supplementary bird feeding significantly alters urban bird communities, boosting introduced species like house sparrows and spotted doves. These effects on avian populations largely disappeared after feeding stopped.
Area of Science:
- Ecology
- Urban Ecology
- Ornithology
Background:
- Food availability is a key factor regulating avian populations.
- Wild bird feeding represents a large-scale supplementary feeding experiment, yet its ecological impacts are understudied.
- Existing research lacks experimental evidence on bird feeding's influence on urban bird communities.
Purpose of the Study:
- To experimentally investigate the effects of supplementary bird feeding on local urban avian assemblages.
- To compare avian community composition, species richness, and species densities between feeding and non-feeding properties.
- To assess the influence of common urban bird feeding practices on native and introduced species.
Main Methods:
- An 18-month experimental feeding study was conducted at 23 residential properties.
- A feeding regime mimicking predominant urban practices was implemented.
- Monthly bird surveys were used to collect data on avian community structure.
Main Results:
- Avian community structure significantly diverged between feeding and non-feeding properties.
- Five common garden bird species showed altered densities due to the feeding regime.
- Introduced species, particularly house sparrow (Passer domesticus) and spotted dove (Streptopelia chinensis), increased dramatically.
- A native insectivore, the grey warbler (Gerygone igata), showed a negative response.
- Most observed changes were temporary and ceased after feeding was withdrawn.
Conclusions:
- Human bird feeding practices significantly shape urban avian community structure.
- Supplementary feeding can alter the balance between native and introduced bird species in urban environments.
- The impacts of bird feeding on avian communities are substantial but potentially reversible upon cessation.
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