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GLIN==> Songbird decline may be linked to non-native shrubs



FROM THE DECEMBER 1999 ISSUE OF "CONSERVATION BIOLOGY"
the journal of the Society for Conservation Biology:
http://conbio.rice.edu/scb/

SONGBIRD DECLINE MAY BE LINKED TO NON-NATIVE SHRUBS

New evidence suggests that the decline of songbirds is linked
to the rise of non-native plants. Birds that nest in non-
native plants lose more eggs to raccoons and other predators,
according to research presented in the December issue of
Conservation Biology.

"Here is an ecological trap if there ever was one!" says
Christopher Whelan of the Illinois Natural History Survey in
Wilmington, Illinois, who co-authored the study with Kenneth
Schmidt of the Department of Biology at the University of
Memphis.

Non-native shrubs are widespread throughout the Midwest and
East Coast. "Introduced honeysuckle and buckthorn can
dominate the understories of forest preserves, particularly
small, fragmented preserves surrounded by urban sprawl," says
Schmidt.

Schmidt and Whelan studied nest predation of American robins
and wood thrushes in a 500-acre deciduous woodland preserve
near Chicago for six years. There, non-native shrubs have
largely replaced the native shrubs where the songbirds once
nested: honeysuckle has replaced arrowwood and buckthorn has
replaced hawthorn.

Schmidt and Whelan found that predation of both robin and
thrush nests was higher in the non-native shrubs than in the
native shrubs and trees. The researchers suggest that this
increase is partly due to physical differences between the
native and non-native shrubs. Buckthorn lacks hawthorn's
sharp thorns, which could deter mammalian predators.
Honeysuckle has sturdier branches, which could both help
predators climb higher and support nests closer to the
ground, where they are more accessible to predators.

Wood thrushes built about half their nests in exotic shrubs.
During the study period, the number of robins nesting in
honeysuckle increased six-fold (from 5% to more than 30%).
The researchers suggest that honeysuckle is an attractive
nesting site because it sometimes leafs out before the native
shrubs.

The good news is that solving the non-native shrub problem
could also help solve the songbird problem. The bad news is
that removing exotic shrubs and restoring natives will be a
big job. But the longer we wait, the worse the problem will
grow.

For more information, contact Kenneth Schmidt (901-678-4408,
or Christopher Whelan (815-476-3134,
virens@attglobal.net).

PHOTOS in slide format of thrushes and robins nesting in
exotic plants are available from Kenneth Schmidt (901-678-
4408, Caracal7@aol.com).

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