Jacinta Humphrey, Research Centre for Future Landscapes, La Trobe University

No matter where you live in Australia, there’s a high chance you’ll spot a bird when you glance out your kitchen window. According to the results of the Aussie Bird Count 2022, this feathered friend will likely be a rainbow lorikeet (Trichoglossus moluccanus), noisy miner (Manorina melanocephala), or an Australian magpie (Cracticus tibicen). Australia is home to a rich diversity of avifauna with approximately 850 species, many of which share our suburbs. Sadly, urbanisation is placing increasing pressure on bird communities, due to the loss and modification of habitat, as well as an increase in anthropogenic disturbances. A recent study of long-term citizen science data indicated that many iconic and common bird species are now declining in major cities, highlighting the urgent need for more research and conservation efforts to protect our avian neighbours.

Image: A New Holland honeyeater perches on a fence in suburban Melbourne. Credit: Lilith Armstrong.

Most studies of urban birds to date have taken a site-level approach, either by comparing bird communities in different land-uses, or examining the habitat features of gardens, streetscapes, and parks that enhance bird diversity. This research has made significant contributions to our understanding of birds in cities, and directly informed wildlife-friendly gardening programs. However, the bird that you see out your kitchen window is unlikely to be solely reliant on your garden. Rather, it will move around the neighbourhood to seek resources from multiple gardens, parks or patches of native vegetation. With this in mind, my supervisors and I hypothesised that urban bird communities may be responding to the physical properties of whole neighbourhoods. So, we designed a study to test this using a landscape-scale approach.

Image: A landscape-scale approach considers the factors that may enhance, or degrade, habitat for fauna on a broader spatial scale. Credit: Jacinta Humphrey.

A ‘landscape’ approach involves collecting data from multiple sites, transects or habitat patches and pooling them together to represent a single landscape, in this case, a residential neighbourhood. We felt this type of study design would be particularly valuable in urban areas because it:

• captures the heterogeneity of land-uses in cities;
• is potentially more relevant to urban planners, local governments and land managers who make decisions on large spatial scales; and
• has direct applications in urban design.

Such an approach may therefore generate novel insights into the properties of urban environments that influence birds and the management actions required to conserve species and communities.

I used a landscape-scale approach to examine the influence of urbanisation on the occurrence of individual bird species, and the richness and composition of avian communities in Melbourne, Australia. I selected 30 residential landscapes (each 100 ha) stratified to represent gradients in housing (9-39%) and canopy tree cover (13-63%). In each landscape, I established 10 survey sites and conducted 50 point-count surveys for birds (five surveys per site). I also used remote sensing to collect data on the physical properties of landscapes, including the cover of housing, canopy trees, open parklands, riparian areas, and intact patches of native vegetation, both within and surrounding a landscape.

Image: An aerial image of one of my study landscapes indicating the 10 survey sites (yellow points), with examples of different land-uses: a-b) residential streets; c) riparian corridor; and d) open parkland. Credit: Aerial photo sourced from Google Earth Pro 7.3.3.7786. Diagram created by Jacinta Humphrey.

My results indicated that birds respond strongly to the properties of ‘whole’ landscapes. Many species responded to a combination of housing and canopy tree cover in urban areas. Responses to housing cover typically were negative, while responses to tree cover were positive for more sensitive species (e.g., laughing kookaburra, Dacelo novaeguineae), but negative for urban-tolerant birds (e.g., little wattlebird, Anthochaera chrysoptera).

Image: The laughing kookaburra had a strong positive relationship with the cover of canopy trees in a landscape. Credit: Rhys Makdissi.

At the community level, I found that up to 82% of variation in avian species richness could be explained by landscape properties. Housing cover was the strongest driver of richness for most bird groups, including native, terrestrial, forest and aquatic species. Surprisingly, canopy tree cover had less influence on richness, although the extent of native vegetation surrounding a landscape had a strong positive impact on forest birds.

The composition of bird communities shifted significantly across the urban-rural gradient and was most strongly influenced by housing, canopy trees and native vegetation. Increases in landscape-scale housing cover resulted in homogenisation of bird communities, meaning that communities in landscapes with high housing density were more similar to each other than those in areas with low housing density. This homogenisation appears to be driven by the progressive loss of forest-dependent birds from residential suburbs.

It’s clear that expanding urban development is having a negative influence on the birds that share our suburbs, but there are ways we can enhance habitat for avian communities. My findings suggest we need to:

• protect patches of intact native vegetation, as these likely provide source areas for forest birds;
• increase canopy tree cover throughout our suburbs to improve habitat suitability for individual species; and
• work collaboratively to monitor and mange birds at the landscape-scale.

If you are interested in my work and would like to receive digital copy of a brochure summarising my findings, please complete this online form.