July 25, 2018, American
Ornithological Society
Land use changes are a major
driver of species declines, but in addition to the habitat to which they're
best adapted, many bird species use "alternative" habitats such as
urban and agricultural land. A new study from The Condor: Ornithological
Applications documents a century of land use change in Illinois and shows
that species' long-term fate can depend on the availability and suitability of
these alternative habitats.
Between 1906 and 1909, a pair of ornithologists
crisscrossed the state of Illinois, creating a unique record of its avian
inhabitants across grassland, forest, urban, and agricultural habitats. The
University of Illinois Urbana-Champaign's Michael Ward and his colleagues
recreated this survey as closely as possible between 2006 and 2008 and used the
data to create mathematical models of bird occupancy, assessing how things had
changed over the course of the twentieth century. They found that birds' use of
alternative habitats had changed more than their use of primary habitats: the
40 species in their analysis that expanded their occupancy did so by making
more use of urban habitats, while the 26 that decreased did so because they
were making less use of agricultural habitats. Urban habitats have become more
bird-friendly in the past century as vegetation has matured and bird feeding
has become more popular. Agriculture, on the other hand, has seen a shift from
small, diversified farms to vast corn and soybean monocultures managed with heavy
herbicide and pesticide use.
"We need to understand how
species use and respond to changes in not only their primary habitat, but also
habitats that they only use occasionally. Species that can take advantage of
alternate habitats can expand their populations," says Ward.
"Understanding which species can or can't take advantage of these
alternative habitats will allow us to better predict which species need
conservation efforts. Urban habitats are the habitats in which many species
have been increasing, and the general public, by providing small bits of habitat in
their backyards, have the opportunity to help a range of species." Species
that have been declining, on the other hand, may rebound if agricultural practices
change to become more wildlife-friendly.
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