Backyards could be a boon for urban birds

Field of Dreams taught us that if you build it, they will come. But the truth isn’t so straightforward, at least when it comes to birds and birdfeeders. Other backyard features are far more likely to entice birds than a fancy-looking seed dispenser. That’s one of a number of findings in a new paper from University of Illinois biologists J. Amy Belaire, Christopher J. Whelan, and Emily S. Minor.

The researchers point out that while parks and preserves are important refuges for urban wildlife, the so-called matrix – which they describe as the “mosaic of land uses between habitat patches” – is equally important. In many ways, it’s easy to manage parks and preserves, since they’re overseen in most cases by municipalities. It is far harder to manage property owners’ yards, which can add up to more than a third of the urban landscape. But if there was a way to manage them, then together they could form corridors that urban wildlife could use to move between larger patches of more natural habitat.

It’s a great idea in theory, but the problem is nobody really knows just what sort of effect managing a neighborhoods’ worth of backyards might have on local ecology. We know more and more about the ecology of individual backyards, and are starting to pay greater attention to cities as a whole, but at the intermediate level of streets or neighborhoods, there is a relative dearth of data.

That hole is precisely what Belaire and her colleagues aimed to fill, and to do it, they turned to Cook County. The county boasts Chicago, the third most populous city in the US, along with some 70,000 acres of forest preserves, most of which are riparian areas along the Chicago and Des Plaines Rivers and their tributaries. Could backyards serve as corridors to allow birds the opportunity to traverse the landscape? To find out, Belaire looked for birds during the June 4 – July 6, 2012 breeding season along transects up to one kilometer away from the forest preserves’ borders.

In addition to the bird surveys, the researchers distributed questionairres to homeowners designed to gather data about the types of plants in their yards, whether they used birdfeeders or birdhouses, and what sorts of water features they might have. They also inquired about the use of pesticides and about whether the home had outdoor pets. That data was evaluated at the yard, street, and landscape levels. Their findings were published this winter in the journal Ecological Applications.

The researchers observed 36 bird species in all, not including wide-ranging birds seen flying far overhead (like hawks). Twelve were year-round natives, 20 were native migratory species, and four were non-native birds. The most common species were American Robins, American Goldfinches, Northern Cardinals, and House Sparrows.

When it came to making for bird-friendly yards, birdfeeders and birdhouses were completely useless. Or, put more formally, there was no statistical relationship between using those devices and having lots of birds.

The most useful levels of analysis were individual yards and streets. Once the researchers zoomed out to the landscape level, the efforts of individual homeowners washed away. When multiple owners in a small area – within a 50 meter zone – did use bird-friendly backyard management strategies, the payoff was clear, and had a larger impact than any landscape level management activities.

So what did attract birds? Trees, for starters. Even better if it was a mix of evergeen and deciduous species, and best if they were mostly natives. In part, trees help to create habitat complexity, especially by adding more vertical habitat diversity. Residential areas are more savannah-like, and by planting trees, homeowners provide more mid- and upper-canopy level vegetation. Having lots of plants with fruits and berries was also a good indicator of bird richness. Together, streets with more bird-friendly yards had almost twice as many species as those without.

Unsurprisingly, the number of outdoor cats on a transect had a negative association with bird richness – with the exception of non-native birds, which were probably just better at avoiding cats. Invasive species, on average, tend to be scrappier than natives. Outdoor dogs were far less problematic, though migratory birds did seem to stay away from transects with more of them. While keeping cats inside keeps all birds safe, keeping dogs inside would still prove beneficial to the most sensitive of bird species.

All that data is great, but what use is it unless homeowners could be convinced to manage their yards in wildlife-friendly ways?

The researchers suggest that people might be more willing to take action when small behavioral changes can lead, in aggregate, to larger positive outcomes. They also suggest that grassroots efforts are more likely to be effective than top-down educational or incentive-based programs. Still, homeowners associations are in a position to motivate homeowners to manage their yards in ideal ways, and municipal programs can also be remarkably effective. The City of Chicago’s Sustainable Backyard Program, for example, offers rebates to residents for actions like replacing exotic with native plants.

Together, Belaire and her colleagues conclude by asking “why not ask more from our residential landscapes?” Indeed, backyards have the potential to be so much more than just a place to enjoy a barbeque or game of catch. – Jason G. Goldman | 15 April 2015

Source: J. Amy Belaire, Christopher J. Whelan, & Emily S. Minor (2015). Having our yards and sharing them too: the collective effects of yards on native bird species in an urban landscape. Ecological Applications 24(8), 2132–2143. DOI: 10.1890/13-2259.1.

Header image: Northern cardinal via shutterstock.com

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