All-American Kestrel Issue of the Journal of Raptor Research
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If you love kestrels and scientific publications, get ready, because we're about to make your week. The June issue of the Journal of Raptor Research focuses exclusively on everyone’s favorite falcon: the American Kestrel. Containing three conservation letters, four short communications, and 16 feature articles, the issue is stuffed with new research on a host of topics including general population trends, tracking devices and data, the effect of various factors on breeding success, and much more. Some of the findings include:
- Data from both fall and winter counts showed American Kestrels declining at both the continental and regional levels—except in western North America, where fall migration counts showed declines but winter counts showed increases. This indicates that western kestrels may be shifting their migration strategies, either migrating shorter distances or not migrating at all. (Oleyar et al. 2023)
- A same-sex pair of banded female kestrels was observed over a five-week period in Texas during the spring of 2020. The pair exhibited several typical kestrel breeding behaviors, including nest-site inspection, territorial defense, and courtship displays. They were also observed copulating dozens of times, with the bird on top during these copulations alternating almost evenly between the two birds. (Bullock et al. 2023)
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A same-sex pair of female American Kestrels was observed in Texas in the spring of 2020. Rather than each bird adopting different sex-specific gender roles, each bird exhibited both typical male and typical female behaviors at various times over the period observed. | Photo by Heather Bullock
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- A 20-year dataset from a box network at the very northern limit of the American Kestrel’s range in the Alaskan Arctic showed no significant trend in occupancy over the course of the study period, though year-to-year occupancy varied greatly. Clutch and brood sizes also remained stable over the study period, while the start of nesting trended slightly later. (Craig et al. 2023)
- 33 American Kestrels in Minnesota were fitted with radio transmitters detectable by the continent-wide Motus automated telemetry network. 11 of the birds were detected by the network while still on their breeding grounds, while 12 were detected a total of 27 times at post-breeding locations, most of these along a migratory pathway through Iowa and Missouri to points further south. (Martell et al. 2023)
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Motus stations are automated receivers that can detect a technically infinite number of individual birds, bats, and even insects fitted with nanotags that emit unique pulse patterns. Over 1,200 stations have been deployed, including this one at the headquarters of our parent organization The Peregrine Fund. A new paper shares results from the use of this technology to track kestrels. | Photo by Matthew Danihel
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- A team in Idaho tracked kestrels using light-level geolocators and satellite transmitters. These methods saw limited success due to a low recovery rate and high device failure rate, respectively, but the project did detect the longest recorded migration path for the species—nearly 3700 mi (6000 km) from Canada to Nicaragua. (Hunt et al. 2023)
- In a study in New Jersey, older kestrels tended to have larger clutch sizes and produce greater numbers of fledglings than those in their first breeding year. Pairs where both adults were older had significantly greater success than young pairs or pairings of an older male and younger female; an older female was never observed paired with a young male. (Snyder & Smallwood 2023)
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A study in New Jersey found that while older male kestrels sometimes paired with young females, older females never paired with young males. Pairs where both adults were older had the greatest breeding success. | Photo by Banook Rodarte
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- A study in Utah tested liver samples from deceased kestrels and blood samples from live adult and nestling kestrels for evidence of anticoagulant rodenticide (AR) exposure. AR residues were detected in 75% of deceased kestrels and 58% of live adult kestrels, but interestingly, just 2% of the nestling kestrels. This finding indicates that adult and nestling kestrels could be getting exposed to ARs in different ways, but further research on these routes of exposure—and the effects of ARs on kestrels, particularly non-lethal ones—is needed. (Buechley et al. 2023)
And there’s more where those came from! Click the link below to check out the issue in its kestrel-tastic entirety.
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New Paper Outlines Potential Problem in Determining Population Trends from Nest Box Data
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It is common practice for many box network coordinators to move nest boxes from unproductive locations to sites where they are more likely to attract kestrels. We at the American Kestrel Partnership (AKP) even recommend this practice in the case of “bad boxes”—boxes that have been installed too closely to stressors such as predators or road noise and have a markedly lower success rates than other nearby nests. However, box relocation can have important consequences when trying to use nest box data to determine whether the local kestrel population is increasing or decreasing.
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A new paper by AKP staff member Dr. Chris McClure has found that increased occupancy in a program's nest boxes do not necessarily mean the local population is increasing. In most programs, poorly performing boxes are relocated to better locations, and this can result in increased box occupancy even if the local population is declining. | Photo by Suzie Bergeron
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A new paper authored by AKP staff member Dr. Chris McClure and published in The Journal of Raptor Research examines this potential pitfall. When nest boxes are moved from unproductive sites to better ones, these boxes’ occupancy and reproduction rates—and therefore those of the entire network—will likely increase. This gives the impression the local population is growing, but this is not necessarily the case. “Because these trends were artificially produced by box relocation, they cannot be extrapolated to the local population as a whole,” notes Dr. McClure. “If poorly performing nest boxes are being relocated, a box program may see increased occupancy and reproduction even if the local population is declining.”
“Potential solutions might include calculating occupancy using only a subset of boxes that were never relocated, or by using statistical models that account for preferential sampling,” Dr. McClure adds. “Determining kestrel population dynamics isn’t as simple as just looking at occupancy trends from nest box programs. It’s important to account for all factors that influence vital rates.”
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American Kestrel Research Featured in Two Prominent Publications
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In addition to maintaining a central database of kestrel breeding data from community and professional scientists, the AKP also supports the work of other researchers, including a team from the University of North Texas (UNT). The UNT project recently took center stage in Audubon magazine, appearing as the cover story for their spring issue.
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The kestrel above was fitted with a field-readable band and GPS tracker as part of a Texas team's efforts to zero in on the age, season, and geographic location where kestrels are most at risk. The shorter satellite antenna detects the bird's position, while the longer radio antenna allows researchers to download tracking data without recapturing the bird. | Photo by Heather Bullock
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“A lot of current research is examining potential causes of decline, but we’re taking a different approach,” says Maddy Kaleta, a UNT graduate student and leader of the project since the fall of 2021. “We’re deploying field-readable bands and GPS trackers on kestrels to track survival and migration patterns, which will allow us to identify at what age, what time of year, and where on the globe kestrels are most experiencing problems. By identifying the where and the when of kestrel decline, we’ll have important clues about the why.”
A second recent article about American Kestrel decline appeared recently in the New York Times. This article also mentions our work in Texas, but goes on to discuss some intriguing early results of a massive modeling project led by The United States Geological Survey (USGS) and the Southwest Region and National Raptor Program of the U.S. Fish and Wildlife Service (USFWS). These preliminary results indicate that lowered survival of young birds in the summer after leaving the nest may be the problem, a finding that some researchers theorize could be tied to a decrease in the availability of the easier-to-catch insect prey juvenile kestrels rely on as they learn to hunt.
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While it's still much too early to draw any firm conclusions, early results from a USGS/USFWS-led modeling project have some researchers speculating that a decrease in the availability of easier-to-catch insect prey may be disproportionately affecting young kestrels during their first few months after fledging. | Photo by Kenneth Martin
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“We’re making progress, but we still have much more to understand before we can call this mystery solved,” comments AKP staff member Dr. Chris McClure, who was quoted in both articles. “American Kestrels are still common enough that they’re not considered threatened at the national level, but it’s important that we identify the causes of their decline and reverse that trend now while the species is still common.”
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Partner Bio: Tami Gingrich
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The year was 2018, and in rural Geauga County, Ohio, Tami Gingrich’s 31-year career as a naturalist and biologist for the Geauga Park District was nearing its end. But before it did, she had one final project in mind. “I had fond memories of assisting the Cleveland Museum of Natural History band kestrels here when I was in high school,” Gingrich reminisces. “Kestrels were plentiful back then, but alas, over the years the population had all but disappeared.”
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Retired biologist Tami Gingrich operates a 25-box network in rural Geauga County east of Cleveland, Ohio. Currently in its fifth breeding season, kestrel occupancy—and public interest—have been climbing steadily. | Photo by Linda Gilbert
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Gingrich hatched a plan to partner with the local community to bring the kestrels back. She and the park district would provide nest boxes and monitor them for activity during the breeding season. Local landowners would mount the boxes on their properties, exclude undesirable tenants such as European Starlings and squirrels, and clean the boxes every winter. To sweeten the deal, Gingrich—a licensed bird bander—offered landowners an up-close look when she banded nestlings. “Our project was designed from the beginning to be a partnership between the park district and local landowners,” she says. “This was always going to be a community effort.”
Armed with 25 boxes built from the park district’s limited budget, she set out to enlist kestrel landlords. According to Gingrich, there are remaining pockets of kestrel habitat throughout the county, but the southeast quadrant holds the largest expanses of rural land, much of it lying within the local Amish community. This led to a unique recruitment method as she pitched the project to the landowners with the greatest promise of hosting kestrel pairs. “I went door-to-door with a box in one hand and plenty of kestrel information in the other,” Gingrich reports. “I felt like a traveling salesperson! I received some strange looks, and not everyone was on board, but overall I was pleased with the positive interest I received.” All 25 boxes were mounted by the winter of 2018, and the project was off and running.
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One of the more popular boxes in the Geauga County network. "This pair never migrated last winter," says Gingrich. "In October they paired up, claimed this box, and vigorously defended it all winter before raising young in it this spring." | Photo by Tami Gingrich
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The Geauga County Amish community has proven a valuable partner as the project’s occupancy numbers have grown. Four of the boxes were occupied each year from 2019–2021; seven were occupied in 2022 and 10 this past breeding season. “Landowners tell me that having a front row seat to a falcon show has been an opportunity of a lifetime,” shares Gingrich. “Watching these beautiful birds of prey rear their young and instruct them how to hunt and survive has given landowners a new appreciation for them, especially when it comes to rodent control.”
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Gingrich invites her kestrel "landlords" to join her for banding sessions, a gesture that has proven extremely popular. "Usually the whole family gets involved," Gingrich reports. | Photo by Tami Gingrich
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Gingrich retired from the Geauga Park District in 2020, but has no intention of leaving the prospering kestrel box project anytime soon. “I am beginning to feel a sense of pride and ownership developing in the community,” smiles Gingrich. “Word is spreading. Interest is growing. After all, it’s not often you have an opportunity to play a first-hand role in the recovery of a species in peril.”
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Box Networks in Two Western U.S. States Need New Homes
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Help wanted! Two kestrel box networks need new coordinators. The first is in Moffatt and the sourrounding counties in northwestern Colorado, where AKP partner Allan Reishus currently monitors a 25-box network. “I will continue to monitor these boxes as long as I am physically able, but I am 76 years old,” he explains. “I have been searching for someone who can take over when I cannot do the work anymore, but that search has thus far been unsuccessful.” Reishus reports that about 90% of his boxes—most of them repurposed plastic Wood Duck boxes that have lasted more than 30 years—are used by kestrels annually.
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Two kestrel box networks—one in Colorado and one in Arizona—are currently in search of new coordinators. Can you help? | Map produced with Google Maps
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The second available network is the Flagstaff Kestrel Project, consisting of 23 boxes spread around Flagstaff, Arizona. “I have permanently moved away from the Flagstaff area and therefore need to find a new home for the project,” explains former Northern Arizona University (NAU) master’s student Maya Rappaport, who founded the project in 2019 but recently graduated. “We’ve contacted our local Audubon chapter, and they are not able to take over monitoring, so we’re looking for other ideas.” With Rappaport no longer in the Flagstaff area, the project’s new contact for inquiries is Rappaport’s former advisor, NAU professor Peter Friederici.
Obviously the ideal solution would be finding someone able to take over these entire networks, but even if you can only take over one box, that would help. Interested partners should reach out to Reishus (areishus8@gmail.com) or Friederici (Peter.Friederici@nau.edu) if you or someone you know is able to get involved.
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As another breeding season winds down, we need to extend our thanks yet again to all of our partners for your contributions to the AKP. Since the beginning of 2023, more than 6,700 observations have been submitted to our database, including more than 1,000 from prior breeding seasons. The nearly 5,700 observations received so far from 2023 already make this our third biggest season ever, with some stats indicating plenty more data is still on the way. Thank you one and all—you are a force for kestrel conservation.
With best wishes,
AKP Staff and Interns
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