How Birds Respond When we Develop Their Habitat
An academic paper published in December by a Seattle-based researcher with ties to Maine sheds some interesting light on the fate of birds in developing suburban landscapes. John Marzluff, the lead scientist on the project, spent a number of years studying common ravens with researcher and author Bernd Heinrich in western Maine. In this recently published study, Marzluff color-banded individual birds from a range of species within the Seattle area. He and his team followed the birds and compared aspects of their life history in relation to whether the area where they originated was in an existing housing development, a park or reserve, or an area that started out as intact habitat but was converted to a housing development during the course of the 10-year study.
Marzluff and colleagues discovered that the bird species could be divided into two types: “avoiders” and “adapters or exploiters.” Bird species that they categorized as “avoiders” included the Swainson’s thrush and the Pacific wren (the Pacific Northwest version of our winter wren). These birds often suffered low reproductive success in areas where development took place and also in existing housing developments. They also tended to move away or die afterwards. These “avoider” species did well in more intact forested habitat in larger parks and preserves, even those within the suburban landscape.
Species in the “adapters or exploiters” category included song sparrow, dark-eyed junco, and Bewick’s wren. These species tended to stay in or near their previous year’s territory and generally had higher rates of reproductive success. “Adapters or exploiters” had higher rates of bird divorce (changing mates) in areas where development occurred but they tended to be able to find a new territory and new mate somewhere nearby.
It’s interesting to consider some of the birds that could fall into these categories in our area and ways it might be possible to attract or retain certain birds in and around our homes and neighborhoods. The first thing that is obvious from a study like this is that if you live near a larger block of healthy, intact habitat—a Boothbay Region Land Trust preserve, for example—you have a higher likelihood of having species that may be “avoiders” nesting on or near your property. We have to speculate to some degree as to what some of those species might be since the study was not done in our area, but they might include birds like winter wren, hermit thrush, brown creeper, and pileated woodpecker.
Even if you have extensive, healthy habitat nearby, there are often specific habitat types or structures that certain birds will need order to be on your property or in your neighborhood. Woodpeckers need some standing dead trees or limbs, for example. Blackburnian and black-throated green warblers need large, old spruces, balsam firs, or hemlocks. The pine warbler will not nest on your property without some pine trees present. Winter wrens are more likely if you have thick brush piles or tangled understory under cool, dark evergreens. Then there are the more obvious bird-attracting features like bird-feeding stations and nest boxes that have been placed for various species.
As we move into spring it might be an opportunity to think about whether you really want to clear the brush or the dead limbs from your property or whether it might be better to leave them for the birds. Consider planting some native, bird-friendly trees, bushes, and flowers as well.