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American Kestrel - Falco sparverius
Topic Started: May 16 2018, 08:07 PM (64 Views)
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American Kestrel - Falco sparverius

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Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Falconiformes
Family: Falconidae
Genus: Falco
Species: Falco sparverius Linnaeus, 1758

Physical Description
The American kestrel (Falco sparverius) is the smallest and most common falcon in North America. It has about a two to one range in size over subspecies and sex, varying in size from about the weight of a Blue Jay to a mourning dove. It also ranges to South America, and is a well established species that has evolved seventeen subspecies adapted to different environments and habitats throughout the Americas. It exhibits sexual dimorphism in size (females being moderately larger) and plumage, although both sexes have a rufous back with noticeable barring. Its plumage is colorful and attractive, and juveniles are similar in plumage to adults. The bird ranges from 22 to 31 cm (8.7 to 12.2 in) in length with a wingspan of 51–61 cm (20–24 in). The female kestrel is larger than the male, though less so than larger falcons, being typically about 10% to 15% larger within a subspecies. The more northern subspecies tend to larger sizes, with a large northern female being about twice the size of a small southern male. The male typically weighs 80–143 g (2.8–5.0 oz), and the female 86–165 g (3.0–5.8 oz). In standard measurements, the wing bone is 16–21 cm (6.3–8.3 in) long, the tail is 11–15 cm (4.3–5.9 in) and the tarsus is 3.2–4 cm (1.3–1.6 in).

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Hunting and Diet
The American kestrel usually hunts in energy conserving fashion by perching and scanning the ground for prey to ambush, though it also hunts from the air. It sometimes hovers in the air with rapid wing beats while homing in on prey. Its diet typically consists of grasshoppers and other insects, lizards, mice, and small birds (e.g. sparrows). This broad diet has contributed to its wide success as a species. It nests in cavities in trees, cliffs, buildings, and other structures. The female lays three to seven eggs, which both sexes help to incubate.

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Its breeding range extends from central and western Alaska across northern Canada to Nova Scotia, and south throughout North America, into central Mexico and the Caribbean. It is a local breeder in Central America and is widely distributed throughout South America. Most birds breeding in Canada and the northern United States migrate south in the winter. It is an occasional vagrant to western Europe.

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American kestrel range
Year Round
Summer (breeding)
Winter (nonbreeding)

Based on appearance and behavior it was for many years considered a member of the primarily European and African kestrel clade within the genus falco, but recent DNA analysis shows the American kestrel to actually be genetically more closely related to the larger American falcons such as the Aplomado falcon, the Peregrine Falcon, and Prairie falcon. Though the species has not been renamed as a result of these genetic analyses, it is not actually a kestrel in the phylogenetic sense. Instead, a process of convergent evolution to fit a similar small prey niche in the ecosystem as the true kestrels has left it with similar physical characteristics and hunting methods.

The American kestrel is a common bird used in falconry, especially by beginners. Though not as strong a flyer as many other larger falcons, proper training and weight control by the falconer allows many American kestrels to become effective hunters of birds in the size range of sparrows and starlings, with occasional success against birds up to approximately twice their own weight.

American kestrels provide important 'ecosystem services'

May 15, 2018 by Cheryl Dybas, National Science Foundation

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A male kestrel in a northern Michigan cherry orchard. Males have gray wings; females, rusty wings. Credit: Catherine Lindell

America's smallest raptor, the American kestrel, can boost economies in Michigan and other fruit-growing states, new research shows. It's the first study to measure regional job creation aided by the activity of native predators.

American kestrels range from Alaska to South America. They dine on bugs, small mammals and fruit-eating birds. More kestrels mean fewer pests, and the tiny hawks' mere presence can produce measurable improvements, said Catherine Lindell, a Michigan State University (MSU) integrative biologist and study co-author. Growers can attract more of these beneficial birds by building nesting boxes.

A paper reporting the results was published today in the Journal of Applied Ecology.

"This research demonstrates that farmers can use science to design agricultural fields that benefit people and wildlife," said Betsy Von Holle, a program director for the National Science Foundation's (NSF) Dynamics of Coupled Natural and Human Systems program, which funded the research.

Lindell and her team calculated the benefit-to-cost ratios of installing kestrel nest boxes around orchards. The results showed that, for every dollar spent, $84 to $357 of sweet cherries are saved from fruit-eating birds.

To scale up the projections, the team used regional economic modeling. The models predicted that increased sweet cherry production from reduced bird damage would generate 46 to 50 jobs, which translates to a major contribution to Michigan's economy.

"Having more American kestrels around orchards reduces the number of fruit-eating birds significantly," Lindell said. "It's not just a microeconomic boost that simply benefits the fruit grower—it has a macroeconomic effect that benefits the state's economy."

Added Von Holle, "Fruit-eating birds avoid orchards with American kestrels, so those with kestrel nest boxes end up producing more cherries. If kestrel nest boxes were used more widely, these researchers estimate, Michigan would benefit by adding new jobs and more than $2 million in increased revenue over a five-year period."

The strategy isn't limited solely to Michigan cherry producers. It's a potential boon for fruit producers throughout the kestrels' range, and is a cost-effective ecosystem service, the scientists said.

Though building nest boxes doesn't always guarantee a booming kestrel population, "installation and maintenance costs of boxes are small, and even if box occupancy rates are low, they can direct kestrel activity to particular places in agricultural landscapes where kestrels can deter birds that are fruit pests," said Megan Shave, MSU integrative biologist and first author of the journal paper.

Although birds make up only 2 percent of kestrels' diets, just having the feathered enforcers in the area keeps many fruit-eating avian species out of orchards. These improvements give fruit growers another, more sustainable option to conventional pesticide-based crop protection, Lindell said.

Stephanie Shwiff and Julie Elser of the U.S. Department of Agriculture's National Wildlife Research Center performed the economic analyses for the study.

Read more at: https://phys.org/news/2018-05-american-kestrels-important-ecosystem.html#jCp

Journal Reference:
Megan E. Shave Stephanie A. Shwiff Julie L. Elser Catherine A. Lindell Falcons using orchard nest boxes reduce fruit eating bird abundances and provide economic benefits for a fruit‐growing region First published: 14 May 2018 https://doi.org/10.1111/1365-2664.13172

1.Suppression of pest species via a native predator is a regulating ecosystem service that has the potential to limit crop damage and produce economic benefits. American kestrels Falco sparverius are widespread, highly mobile, generalist predators that hunt in human‐dominated habitats and have the potential to provide previously undocumented ecosystem services in agricultural landscapes.

2.We hypothesized that kestrel activity associated with nest boxes and artificial perches acts to increase perceived predation risk that, in combination with direct predation, can reduce fruit‐eating bird abundances in orchards. We used counts and observations of fruit eating birds from fixed‐width transect surveys to investigate variation in bird abundances and to estimate sweet cherry loss in cherry orchards with and without active kestrel boxes. We also conducted a benefit‐cost analysis of nest box installation and used regional economic modelling to estimate macroeconomic impacts of increased sweet cherry production in Michigan, an important US fruit‐production region.

3.Fruit eating bird counts were significantly lower at orchards with active kestrel boxes. Although kestrels used the perches in young orchard blocks and may benefit from them, the presence of perches did not have a significant effect on bird counts.

4.Benefit‐cost ratios for kestrel nest boxes indicated that for every dollar spent on nest boxes, $84 to $357 of sweet cherries would be saved from fruit eating birds. Regional economic modelling predicted that increased sweet cherry production from reduced bird damage would result in 46 to 50 jobs created and $2.2 million to $2.4 million in increased income for the state of Michigan over a five‐year period.

5.Synthesis and applications. Kestrel nest boxes in sweet cherry orchards provide a highly cost‐effective ecosystem service with potential reverberating benefits for a regional economy. Box occupancy rates will undoubtedly vary across landscapes and regions. However, costs to install and maintain boxes are small and, even if box occupancy rates are low, boxes can direct kestrel activity to particular places in agricultural landscapes where they can deter pest birds. Thus, the potential benefits for fruit crops greatly outweigh the costs of this pest management strategy.

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