Sprawl may threaten wildlife i...( high-elevation aspen stands. Han...)

Hansen and Rotella found that most of the bird hotspots were on or near private lands, which were mostly at low elevations. Only about 7% of the bird hotspots were in reserves, which were mostly at higher elevations. In addition, rural residential development was concentrated near the bird hotspots on private lands. Home densities were nearly 70% higher within about a mile of hotspots than elsewhere on private lands.

The proximity of development to the low-elevation hotspots could mean trouble for the birds. Hansen and Rotella found that robins may depend on the low-elevation hotspots: the results suggest that robin populations are increasing in the cottonwood but not in the aspen sites. The researchers attribute this to the fact that the robin nesting season is two weeks longer in the low-elevation cottonwoods than in the high-elevation aspen, giving females more opportunity to renest.

The researchers also found that yellow warblers may already be threatened by development. The results suggest that even though more females are renesting in the cottonwoods presumably because robins chase these parasites away. Robins also chase potential nest predators.

The birds' dependence on hotspots on private lands and the yellow warbler's vulnerability to development suggest that reserves may not be enough to protect biodiversity. "These trends cast doubt on the viability of current strategies that rely on nature reserves for wildlife conservation and ignore intervening lands. Conservation strategies to protect population source areas outside reserves are likely necessary to reduce rates of future extinction in nature reserves," say Hansen and Rotella. Their work could help managers figure out which lands outside of reserves should be protected.

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Contact: Andrew Hansen
hansen@montana.edu
406-994-6046
Society for Conservation Biology
22-Jul-2002