UF Study: Developed Shoreline May Attract, Not Deter, Water Birds

July 1, 2004

GAINESVILLE, Fla. — Though widely perceived as “unnatural” or harmful to wildlife, lakefront residential developments actually appear to be favored hangouts for many water birds, according to a University of Florida study.

In fact, several species of birds seem to prefer, or even seek out, developed shoreline, at least on urban lakes, said Mark Hostetler, an extension wildlife specialist with UF’s Institute of Food and Agricultural Sciences.

“It seems that when people build on the shore of a lake, they can inadvertently create good feeding habitat for a variety of water birds,” said Hostetler, co-author of an article about the study published in the July issue of the journal Landscape and Urban Planning. “And it seems that, while birds don’t like to be disturbed by people, they’ll put up with a human presence if it means having access to better feeding habitat.

“That doesn’t mean that development is good for birds in the grand scheme of things,” he said. “But it does show that people can manage their landscape to make developed areas a good habitat for birds.”

In 2001 and 2002, Hostetler and graduate student Ashley Traut spent two winter months and two summer months counting 35 species of indigenous birds on lakes in Winter Haven, a city of about 26,000 people in the rapidly growing I-4 corridor of Central Florida. All four of the lakes – Jessie, Deer, Buckeye and Conine – were natural lakes, and all four had shorelines that were partly developed and partly undeveloped.

The researchers found a stark difference between bird populations on developed and undeveloped shorelines on each lake. On Buckeye Lake – the least developed of the four with 59 percent of its shoreline built out – they sighted 409 birds in developed areas and 139 birds in undeveloped areas. On Deer Lake – the most developed lake with buildings along 79 percent of its shoreline – the researchers counted 2,463 birds in developed areas compared to 150 birds spotted in undeveloped areas.

While the researchers have yet to pinpoint a cause for the population differences, they say it’s likely that birds and landowners seem to have similar taste in waterfront landscape features.

Seeking better views of the water, Hostetler said, lakefront property owners tend to clear away tall, dense aquatic vegetation – foliage that also interferes with the foraging habits of some wading birds such as the great egret. Docks and boat houses attract diving birds because they provide a perch above deep water, he said. Lawns provide foraging conditions favored by the white ibis and the cattle egret, Hostetler said, and may attract other birds by providing them with a place where they can easily see, and run away from, approaching predators.

On all four urban lakes, undeveloped shoreline consisted of small patches of forest, where stands of tall, dense vegetation grew in water near the shore. Only two of the 35 species of birds – the least bittern and the green heron – were found in greater numbers in these seemingly less-disturbed areas.

Studies by other researchers, Hostelter said, have shown that many wetland birds prefer “hemi-marsh” conditions – environments that provide a mixture of tall aquatic plants, open water, floating vegetation and some trees along the shoreline. On the four lakes in the study, undeveloped areas were dominated by tall vegetation, while developed areas had more of the variety associated with hemi-marsh conditions.

Still, Hostetler said, hemi-marsh conditions can be found on lakes that have never been touched by development.

“This study doesn’t compare developed lakefront to completely undeveloped urban lakes,” he said. “All the lakes in the study are in an urbanized area, and we just compared developed shoreline on those lakes with undeveloped shoreline.”

The study did not measure whether birds prefer urban lakes to rural lakes. Hostetler said it is likely many species, cautious of human presence, avoid urban lakes altogether. Several of the birds in the study also require tall vegetation during the breeding season, he said.

Mark Kraus, deputy director of Audubon of Florida, said he’s not surprised that bird counts were higher on developed lakefront, though he hopes people don’t use the results to “write developers a blank check,” he said.

“It makes sense that at least some birds would prefer to feed in places where there’s less vegetation, if only because it decreases their chance of being surprised by a predator,” he said. “That doesn’t mean the birds are better off because someone built a house on the lake.”

Kraus said the ill effects of urbanization – such as fertilizer-laden runoff, which damages aquatic life in lakes – are often invisible to landowners.

Hostetler said the study points to a need for more research on urban lakes as bird habitat and more attention to bird-friendly landscaping on existing urban lakes. Landowners, he said, could make an effort to better replicate “hemi-marsh” conditions on and around their property, making those areas still more bird-friendly and creating habitat for birds that still shun developed areas.

“What we’ve found is that many kinds of birds are able to adapt to a human presence and even use the built environment to their advantage,” he said. “In the past, urban lakes have been thought of as having little wildlife value, but we can add quite a bit to that value if we manage the landscape properly.”