of Blackbirds, Crows, and Starlings from
by Ron Johnson, Extension Wildlife Specialist,
University of Nebraska Cooperative Exension.
Reprinted with permission by Soni Cochran, Extension Associate
Odor, noise, filth
concerns - Histoplasmosis: The soil in older roosts may harbor
fungal spores of this human respiratory disease. Exposure
is most likely when dry roost substrate is disturbed.
trees: When roosts occur in landscape trees near homes or
along streets, thinning side branches from the trees used by
birds will usually disperse them. This method was developed
from blackbird roost studies in Texas and appears to be an effective
approach. Consultation with a professional arborist will help
maintain the trees' aesthetic qualities.
or grove of trees: Thin out about one-third of the trees.
Generally, such roosts occur in dense, overcrowded stands of
young trees; thinning improves tree growth and makes the site
unsuitable for roosting. Such thinning successfully dispersed
roosts from research woodlots in Ohio and Kentucky, and from
at least two problem roost situations in Nebraska. In dense
cedar thickets, bulldozing strips through the roost to remove
one-third of the habitat has also been successful in dispersing
birds. Soil disturbance with heavy equipment, however, may be
hazardous if soils harbor fungal spores of histoplasmosis.
Selection: If planting trees in an area with a history of
bird roost problems, avoid trees that have a more closed or
dense canopy. For example, fall blackbird/starling roosts appear
more likely to occur in trees such as maples, Bradford pear
in protected spots, and, to a lesser extent, pin oak. Roosting
flocks generally choose dense trees that offer ample perch sites
for the large flock and protection from adverse weather. Another
point to consider in a landscape plan is that a mix of tree
types is less likely to be suitable as a roost site, compared
to use of a single species grouping.
early before birds form a strong attachment to the site.
*Be persistent until the problem is solved.
*Dispersing a roost by frightening will likely require 3 or
more consecutive evenings to be successful.
devices include recorded distress or alarm calls, gas-operated
exploders, battery- operated alarms, pyrotechnics (shellcrackers,
bird bombs-contact a professional pest control operator and
city ordinances for regulations/permits/restrictions), lights
(for roosting sites at night), bright objects, and various other
stimuli. Spraying birds with water from a hose or from sprinklers
mounted in the roost trees has helped in some situations. Beating
on tin sheets or barrels with clubs also scares birds.
combination of several scare techniques used together works
better than a single technique used alone. Vary the location,
intensity, and types of scare devices to increase their effectiveness.
to dispersal efforts, consider alerting public officials and
neighbors as appropriate about the possible disturbance and
about the purpose of the dispersal. Consider also where dispersing
birds might go.
tape recorded crow call successfully dispersed crows from individual
urban roosts in a recent California study. Crows took flight,
circled overhead giving assembly and scolding calls. Crows from
nearby roosts flew in and joined. At the end, all crows flew
away and left the roosts empty. Study details: The tape was
played ~30 seconds on and ~30 seconds off for 4 to 5 times within
a 5 minute period. Test 1: 4 roosts; tape played for 3 consecutive
nights; roost observed for next 5 nights. Test 2: 1 roost; tape
played for 3 nights plus as needed (3 additional nights) to
prevent crow return; roost observed for 31 days. Test 3: all
roosts in town (20 roosts); tape played for 5 days; roosts observed
for 5 more days. Commercially available tape used: "Death Cry
of a Crow" (Johnny Stewart, Box 7594, Waco, TX 76710; 817-772-3261).
This is the "squalling call" and is also available as "distress
call" from Cornell Lab of Ornithology, Library of Natural Sounds,
159 Sapsucker Woods Rd., Ithaca, NY 14850; 607-254-2406). Before
such dispersal is attempted, consider where roosting crows might
June 5, 2002
W. P., and T. P. Salmon. 1993. Tape-recorded calls disperse
American Crows from urban roosts. Wildl. Soc. Bull. 21:334-338.
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