Supplementary feeding restructures urban bird communities.
Food availability is a primary driver of avian population regulation. However, few studies have considered the effects of what is essentially a massive supplementary feeding experiment: the practice of wild bird feeding. Bird feeding has been posited as an important factor influencing the structure of bird communities, especially in urban areas, although experimental evidence to support this is almost entirely lacking. We carried out an 18-mo experimental feeding study at 23 residential properties to investigate the effects of bird feeding on local urban avian assemblages. Our feeding regime was based on predominant urban feeding practices in our region. We used monthly bird surveys to compare avian community composition, species richness, and the densities of local species at feeding and nonfeeding properties. Avian community structure diverged at feeding properties and five of the commonest garden bird species were affected by the experimental feeding regime. Introduced birds particularly benefitted, with dramatic increases observed in the abundances of house sparrow (Passer domesticus) and spotted dove (Streptopelia chinensis) in particular. We also found evidence of a negative effect on the abundance of a native insectivore, the grey warbler (Gerygone igata). Almost all of the observed changes did not persist once feeding had ceased. Our study directly demonstrates that the human pastime of bird feeding substantially contributes to the structure of avian community in urban areas, potentially altering the balance between native and introduced species.
Centre for Biodiversity and Biosecurity, School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand; and jgal026@aucklanduni.ac.nz.
Josie A
JA
Galbraith
Centre for Biodiversity and Biosecurity, School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand; and.
Jacqueline R
http://orcid.org/0000-0002-2112-2803
JR
Beggs
Environmental Futures Research Institute and School of Environment, Griffith University, Nathan, QLD 4111, Australia.
Darryl N
DN
Jones
Centre for Biodiversity and Biosecurity, School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand; and.
Margaret C
MC
Stanley
D000704:Analysis of Variance; D000818:Animals; D058448:Biota; D001717:Birds / Q000502:physiology*; D002947:Cities; D005248:Feeding Methods / Q000662:veterinary*; D006801:Humans; D058865:Introduced Species; D009520:New Zealand; D011156:Population Density
avian ecology; community composition; garden birds; human interactions; wildlife feeding