February 2019 - 22

American kestrel: IPM friend for growers
By Marie Flanagan
North Central SARE
Cherry producers across the region are
all too familiar with starlings, finches,
voles, pocket gophers, and other animals
that can wreak havoc on a cherry
orchard by feeding on ripening fruit and
developing roots or shoots. These little
pests can be a big problem for Michigan's
cherry growers, who grow 75 percent of
all tart cherries and 20 percent of sweet
cherries in the U.S.
Natural predators such as raptors
will feed on some of the smaller bird
and mammal species, and American
kestrels are among the raptors that
some growers are working to attract.
Although they offer potential usefulness
for fruit growers, the National Audubon
Society and the Raptor Population Index
indicate that American kestrels
have experienced a 47 percent decline
across North America. In Michigan,
their numbers have been reduced by 28
to 43 percent, depending on the region.
" The American kestrel is a
widespread species of falcon that has
shown long-term population declines
due in part to loss of natural nesting
cavities, " said Michigan State University
(MSU) graduate student Megan Shave.
" However, kestrels readily use nest
boxes, which allow for breeding in
areas that may provide valuable hunting
habitat, such as agricultural areas. "
Shave was first introduced to raptors
as an intern at the Manomet Bird
Observatory, where she banded a number
of sharpshinned, Cooper's and redshouldered
hawks. She had never worked
with American kestrels previously, but
saw an opportunity with kestrel nest boxes
in the cherry-growing region of Leelanau
County, Michigan. A few people
had installed nest boxes in the region
previously, and some growers were already
interested in them for pest management.
With a $9,959 NCR-SARE Graduate
Student grant, Shave and her team
worked directly with eleven cherry
growers in Leelanau County to explore
the effectiveness of habitat enhancement
for kestrels. They installed 25 new nest
boxes and monitored kestrel and prey
abundances. They tracked kestrel and
orchard pest behavior with a variety
of technologies including weatherproof
cameras with night vision and GPS
data loggers.
The kestrels provisioned their young
with a variety of orchard pests, including
grasshoppers, voles, and fruit-eating
birds. Although the kestrels did not bring
birds to their nests as frequently as small
mammal and insect prey, Shave found
that fruit-eating birds were less abundant
in orchards with active kestrel boxes,
perhaps because they were deterred by
the presence of kestrels. All of this was
good news for growers.
" I've had a nesting pair of kestrels for
many years now, and I just don't have
bird problems nearly as bad as I did
before, " said Jim Nugent, chair of the
Michigan Tree Fruit Commission and
owner of Sunblossom Orchards
in Leelanau County. " I absolutely
recommend them (nesting boxes),
especially for sweet cherry orchards.
I always felt they were effective, but
now, with the MSU study, we have data
to back that up. "
Through subsequent outside grant
funding, the team was able to conduct
a benefit - cost analysis of nest box
installation. They concluded that
for every dollar spent on nest boxes,
$84 to $357 of sweet cherries would
be saved. Expanding on that, regional
economic modeling predicted that
increased sweet cherry production from
reduced bird damage would result in
46-50 jobs created and $2.2 million to
$2.4 million in increased income for the
state of Michigan over a 5-year period.
Their findings have prompted an
expansion of the nest box program
into the blueberry growing region of
southwestern Michigan. Additionally,
ongoing research will use a national
survey of fruit growers and inperson
interviews, along with modeling
approaches, to determine the factors that
influence growers to use predator nest
boxes as a pest management practice.
" Kestrel nest boxes in sweet cherry
orchards provide a highly cost-effective
ecosystem service with potential
reverberating benefits for a regional
economy, " said Shave. " Given the
low cost to install and maintain a
Researchers at Michigan State University are learning more about the American kestrel and
its potential benefit to cherry and blueberry growers. Photo: Megan Shave
0.30%
2.28%
1.95%
13.55%
0.06%
0.26%
0.27%
Arthropod
Mammal
Bird
Annelid
Herptile
Mollusc
81.33%
Unidentifiable invertebrate
Unidentifiable vertebrate
DELIVERIES= 7,778 RECORDING DAYS= 179 NEST BOXES= 15
Source: SARE
kestrel nest box, I think our results
could encourage more growers to start
considering habitat improvements
as a part of their integrative pest
management strategies. "
The team has presented its results at
the North Central region at expos and
workshops, and at the 28th Vertebrate
Pest Conference in California.
Want more information? See the
related SARE grant(s) GNC15211,
Evaluating Agricultural
Applications of Orchard Nest Boxes and
Perches for a Declining Raptor Species:
Quantifying Impacts on Pest Rodents
and Birds. FGN
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February 2019

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