Late for an important date: consequences of mistimed nesting for American kestrels

It’s not only Alice in Wonderland’s White Rabbit that faces dire consequences for being late. Animals that fail to synchronize the most taxing part of the breeding season (i.e. raising young) with peak food availability can become “mismatched” with their food sources, meaning there might not be enough food for themselves and their offspring. With climate change causing earlier vegetation green-up (one of the first signs of spring) in many regions, animals that don’t keep up by breeding earlier are increasingly at risk of mismatch.

Spring flowers in bloom (left), mouse hiding in a nestbox (top right), female American kestrel flying (bottom right)

American kestrels are widespread, generalist predators that breed across much of North America. Although populations in the West are responding to earlier springs by nesting earlier, populations in the East do not seem to be shifting nesting timing. These regional differences, along with widespread population declines (particularly in eastern populations), makes the American kestrel a prime candidate to study the effects of climate-driven mismatch. We set out to uncover the consequences of mismatch on survival and reproduction of American kestrels to gain insights into whether and how this species will adapt to changing climate.

Remote trail camera photos from inside nestboxes. From left to right: female and male kestrel roosting overnight, male kestrel incubating, female kestrel incubating, four kestrel eggs, male and female kestrel with newly hatched nestlings, newly hatched nestling with 3 unhatched eggs, four young nestlings, at least three female nestlings near fledging age

If mismatch is affecting kestrel reproduction, we might expect to see that mismatched nests will fail completely (i.e. produce no offspring) or will produce fewer offspring. To investigate this, we used nesting data collected by professional and community scientists from >2000 nests across the American kestrel breeding range in the United States and Canada (sources: Cornell Lab of Ornithology’s NestWatch, The Peregrine Fund’s American Kestrel Partnership, Southwestern Idaho Kestrel Study, Full Cycle Phenology Project on Department of Defense installations). We measured mismatch by calculating the difference in days between the date of “start of spring” at the nest location (based on temperature and first bloom dates) and the date the first egg was laid. Our results showed that “late” nests (i.e. eggs laid after the start of spring) were more likely to fail, and those that didn’t fail produced fewer offspring compared to “early” nests (i.e. eggs laid before the start of spring). Effects of late nesting were particularly severe for kestrels nesting in the Northeast compared to other regions, with early nesters producing a high number of offspring and that number dropping sharply the later they nested. (see the full paper here)

Visual representations of above results:
The top panel represents a highly seasonal environment (peaked green resource curve) where American kestrels that lay eggs early (shown in orange) overlap with food peaks resulting in a very high number of offspring and those that lay eggs late (shown in purple) miss the food peak resulting in a very low number of offspring.

The bottom panel represents a less seasonal environment (low, even green resource curve) where American kestrels that lay eggs early (orange) overlap more with food peaks resulting in more offspring compared to those that lay eggs late (purple) and overlap less with food peaks, but the difference is less pronounced that in more seasonal environments.

Raising young takes a lot of energy and resources, and parents who raise young in mismatched conditions when food is limited may be less likely to survive than parents who nest on time. To investigate this, we needed in-depth information about the year-to-year survival of kestrels, so we used data from two intensive long-term nestbox monitoring sites in western (Idaho-Julie Heath & Karen Steenhof, Boise State University) and eastern (New Jersey-John Smallwood & Emilie Snyder, Montclair State University) North America. At these sites, researchers attached leg bands with unique identifying numbers to each kestrel, to determine who was surviving and breeding successfully year-to-year. Our results showed interesting differences between the western and eastern populations. In the West, kestrels that nested early were more likely to survive than later nesters, but in the East, the opposite was true, kestrels that nested later were more likely to survive than earlier nesters. (see the full paper here)

Male American kestrel with identifying leg band (left), female American kestrel feeding nestlings (right)

Interestingly, kestrels that lay eggs too late may engage in behavior to compensate for their mistiming. Using remote trail cameras in a subset of nestboxes on Department of Defense sites, we found that for kestrel pairs that nested later, males began incubation sooner after eggs were laid than males from pairs that nested earlier. This early incubation resulted in eggs hatching sooner (i.e. making them less mismatched with food peaks) and resulted in hatch asynchrony (i.e. offspring hatching on staggered days). Having offspring that reach their peak growth rate at different times lessens the per diem energy burden on parents, which may help them survive and raise young successfully even when mismatched with food peaks.

Visual representations of above results:
The top panel (orange) represents early nesting kestrels where males begin incubation once all eggs have been laid, resulting in offspring hatching at the same time (i.e. all the same age).

The bottom panel (purple) represents late nesting kestrels where males begin incubation before all eggs have been laid, resulting in offspring hatching on different days (i.e. different ages)

In sum, we demonstrate that American kestrels are vulnerable to consequences of mismatch and that this vulnerability varies across their breeding range. In the West, nesting earlier seems to provide benefits for both survival and reproduction, which may explain why western populations are nesting earlier in response to earlier springs. Whereas in the East, a trade-off between the survival costs for parents versus the reproductive benefits of nesting early may explain why nesting timing remains unchanged. Although we don’t know what the root cause of these regional differences is, it may be related to the length of nesting windows or other climate-driven changes in weather patterns. In the West, the growing season is long, and as climate change drives warmer winters and earlier springs, constraints on early nesting are being removed, widening the window of time kestrels can nest. In the East, the growing season is shorter and more peaked, and climate change is resulting in more extreme early season weather which may constrict the window of time kestrels can nest safely. Although the early onset of incubation may be an adaptive behavior to deal with nesting too late, it is unknown how effective this will be in offsetting consequences of mismatch.

This research is supported by the U.S. Department of Defense, through the Strategic Environmental Research and Development Program (SERDP RC-2702).

Thank you to our collaborators and coauthors, our amazing field team, and the countless community scientists who contributed data. Special thanks to the DoD biologists and volunteers across 12 DoD sites who installed and monitored nest boxes and cameras, and provided invaluable on-the-ground help with logistics, camera troubleshooting, and much more.

Post by-Anjolene Hunt

Read the full scientific publications this blog was based on here:
Callery, K. R., Schulwitz, S. E., Hunt, A. R., Winiarski, J. M., McClure, C. J., Fischer, R. A., & Heath, J. A. (2022). Phenology effects on productivity and hatching-asynchrony of American kestrels (Falco sparverius) across a continent. Global Ecology and Conservation36, e02124.

Callery, K. R., Smallwood, J. A., Hunt, A. R., Snyder, E. R., & Heath, J. A. (2022). Seasonal trends in adult apparent survival and reproductive trade-offs reveal potential constraints to earlier nesting in a migratory bird. Oecologia199(1), 91-102.


Collaboration and remote monitoring during the COVID-19 pandemic

As many people and businesses face stay-at-home orders to protect themselves and others from COVID-19, biologists also face hurdles in conducting field research. Field research involves traveling to remote sites, often in pairs or groups, to survey, monitor, and collect samples from wildlife. With the current pandemic situation, much of this research has been temporarily shut down, or drastically altered, and involves constantly updating plans as the conditions and restrictions change on a state-to-state and site-to-site basis.

Our Full Cycle Phenology project uses a variety of methods to collect large-scale data on American Kestrel annual cycles. A large component of the project involves crew travel to Department of Defense (DoD) sites across 13 states to capture, band and sample breeding American Kestrels, to perform camera maintenance and data downloads. Needless to say, travel restrictions imposed for Boise State Employees, restrictions for non-local and non-essential employees working on DoD installations, and general stay-at-home orders have made this aspect of the project impossible. Even without these restrictions, the general risk of traveling and exposing our crews to high density areas like airports and regions with high community spread of the virus, and the unavailability of PPE to protect crew members, was not acceptable.

Map showing the Department of Defense sites where we monitor nest boxes for American Kestrels, lines indicate connections between our base in Boise, Idaho and each site (left). A male American Kestrel we captured, banded, and collected biological samples from in previous years.

Fortunately, several aspects of this project make it possible for us to salvage some data collection this year, the final year of fieldwork for the project. We are are incredibly fortunate to have many willing and capable collaborators among the biologists working on DoD installations. These partners have been essential throughout the project in providing on-the-ground assistance with logistical planning, installation access, and periodic nest box monitoring. This year, our partners have stepped up again and provided invaluable assistance by deploying cameras, and collecting samples at sites where biologists are still allowed on installations.

Above images show our DoD and other local partners helping to install nest boxes, cameras, and perform maintenance.

Images from cameras in nest boxes provide a wealth of information on phenology, breeding behavior, and productivity of American Kestrels and other species using the nest boxes. Furthermore, many of these cameras send data remotely on a cellular service, so we are able to monitor nests remotely from our homes in Boise, Idaho!

We are so grateful for the opportunity to work with this fantastic network of people, and to be able to continue learning about kestrels remotely. We hope you follow along with us and enjoy watching the wonders of the natural world from the comfort of your home!

Our remote trail cameras capture a male and female American Kestrel pair roosting together at night in a nest box in Yakima Training Area, Washington (far left); and a female (center left) and male (far right) taking turns incubating their clutch of five eggs (center right) in White Sands Missile Range, New Mexico

Our remote cameras have also captured images of nesting screech owls (upper three photos); squirrel pups (two lower left photos); and nesting bluebirds (two lower right photos) at sites such as Eglin AFB, Florida, and Fort Bragg, North Carolina

2019 Breeding Season Summary

As we gear up for the final breeding season of the Full Cycle Phenology project, here’s a look back at the 2019 breeding season.

Phenology Data Collection

From trail cam photos inside nest boxes and in-person visits, we collected timing information such as: the date kestrels arrived in nest boxes, when they laid eggs, when eggs hatched, and when nestlings fledged from the box. We conducted >1000 in-person nest box visits across Department of Defense (DoD) sites, and collected  >150,000 images from inside nest boxes over the 2019 breeding season.

Our team of research technicians and graduate students are currently going through thousands of images and recording data from each image (i.e. nest status; presence, sex, and count of adult kestrels, eggs, nestlings; incubation behavior) using the ViXen image processing program. These data will be used to understand the timing of breeding behavior and the consequences of timing on productivity and survival.

Kestrels occupied 49 of 242 nest boxes at seven of our 12 DoD sites in 2019 (
Figure 1), ranging from one occupied nest at Big Oaks National Wildlife Refuge, Indiana, to 15 occupied nests at Yakima Training Center, Washington. No kestrels nested at our DoD sites in Alaska, Texas, Florida, North Carolina, North Dakota, or California in 2019. However, we did have several other cavity-nesting species that used our boxes including: buffleheads, screech owls, bluebirds, tufted titmice, and several squirrel species! 

Figure 1. Map of American Kestrel nest outcomes in nest boxes on Department of Defense installations. Circles represent DoD sites where nest boxes were occupied, the size of the circle represents the total number of occupied boxes (ranging from 1-15), and the color represents the proportion of “successful” nests (i.e. where ≥1 nestling fledged) at that site, ranging from 0 (light blue; all nests failed) to 1 (dark blue; all nests were successful)


The majority of these nesting attempts (30/49) were “successful” (i.e. at least one nestling survived to fledging age). Most nest failures occurred at the egg stage (i.e. abandonment by adults or eggs predated), although a few failures occurred at the nestling stage (i.e. nestlings predated).

Genetic and Isotopic Data Collection

Using real-time information from cellular cameras and from communication with DoD biologists, our Boise State University crew conducted trips to DoD sites with nest boxes occupied by American Kestrels. We captured adult and nestling kestrels to attach unique identifying bands, take measurements, and collect genetic samples (from feathers) and isotopic samples (from claw clippings).

From April to August 2019, we banded and collected biological samples from 198 kestrels (56 breeding adults and 142 nestlings) across seven DoD sites (Figure 1). In addition, we collected samples from adult kestrels in southern Saskatchewan (n = 7), Canada, and from nestling kestrels in Fairbanks, Alaska (n = 2).

The combination of phenology data and biological sample data will be used to test relationships between genetic and isotopic signatures of individual kestrels and regional populations with the timing of breeding.

Stay tuned for more updates on our research as we head into the final breeding season of the Full Cycle Phenology project!

This research is supported by the U.S. Department of Defense, through the Strategic Environmental Research and Development Program (SERDP RC-2702).
Special thanks to the 19 DoD biologists and volunteers across 12 DoD sites who monitored nest boxes and provided invaluable on-the-ground help with logistics, camera troubleshooting, and species identification.
Post by-Anjolene Hunt

SERDP-ESTCP Webinar- Using Partnerships & a Full Annual Cycle Framework to Forecast Species Responses to Climate Change

This month, our Principal Investigator Dr. Julie Heath and PhD student Jay Winiarski presented a webinar on our Full Cycle Phenology research as part of the Strategic Environmental Research and Development Program (SERDP) & Environmental Security Technology Certification Program (ESTCP) biweekly webinar series.

Julie presented on: “Partnerships Enhance Scope and Scale of Phenology Research”, while Jay presented on: “Full Annual Cycle Framework for Forecasting Species Responses to Climate Change” 

Watch the full webinar here:

Thank you to SERDP-ESTCP for supporting the Full Cycle Phenology project, and for the opportunity to present this webinar.



Birds Across Borders: Tri-national kestrel collaboration

For thousands of years migratory birds have made annual journeys from their breeding to wintering grounds, following the seasonal availability of resources. While topographic features like mountain ranges and oceans shape migration routes and destinations, geopolitical boundaries like countries are of little consequence to birds. This inherent international nature of long-distance migratory birds means that studying them takes large-scale international collaboration and cooperation.

American Kestrels are widespread across the Americas, breeding in much of Canada and the U.S. and wintering in the U.S, Mexico, and Central America. Fortunately, because of this widespread distribution and charismatic and conspicuous nature, many professional and citizen scientists are studying them across their range. This large network has allowed groups like ourselves and the American Kestrel Partnership to examine large-scale patterns and variation.


Over the past two years, the Full Cycle Phenology project has had the incredible opportunity to conduct kestrel field research with amazing collaborators in Canada, the United States, and most recently, Mexico, making our work feel truly international.

We had such a phenomenal experience in Mexico this past winter, that we wanted to share some highlights here. Our mission was to capture kestrels wintering in Mexico to attach identifying bands, take genetic (feathers) and isotopic (claw clips) samples, take measurements, and potentially attach gps transmitters. Through this combination of methods we hope to understand more about the breeding origin and migratory status of these birds.

We began our work in the state of Veracruz, where lush tropical forests, beaches and wetlands along the Gulf coast were interspersed with colorful rural mountain towns and sugar cane crops on the verge of harvest.  While on our previous travels, we were used to seeing kestrels conspicuously perched on power lines along open fields, here they were tough to spot through the dense vegetation, not to mention the lack of power lines in many areas! Despite these challenges, we were able to capture 8 kestrels in Veracruz.

Crossing over the Sierra Madre mountains into the state of Puebla, the landscape and climate changed dramatically, from lush greenery to dry, arid desert. The wide open fields, and availability of power lines, made it much easier to spot birds. Now our main challenge was battling the stifling dry heat, and trying to keep our low-clearance minivan from disaster on the rough dirt roads with no shoulders. We captured another 8 kestrels on the west side of the mountains, including one in view of an active volcano! (Popocatépetl)

In addition to kestrels, Veracruz and Puebla were rife with stunning wildlife! We saw three other falcon species: Bat falcons, Laughing falcons, and Aplomado falcons, as well as numerous other bird species! 


As is always evident on these trips, American Kestrels are potentially a highly adaptable species, found in many geographic and climatic regions, with a variety of migratory strategies. Understanding whether genetic traits/plasticity, and climate are influencing shifts in phenology will be important in predicting effects of global change on this species, and others.

Although the birds were our main focus, it was just as important that we got to spend time working with and learning from researchers in another country. We got to exchange knowledge about how ornithological research and conservation works in our respective countries, practice common banding and field terminology in both english and spanish, and plan future collaboration. This tri-national team: myself (a Canadian biologist working for Boise State University), Jesse Watson (an American biologist working for Hawkwatch International), and Kashmir Wolf and Dayan Espinosa (Mexican biologists working for Pronatura Veracruz) truly exemplified the relationships between people and organizations across borders that are vital to conducting research on migratory species and global change ecology.

¡Muchas gracias a nuestros maravillosos anfitriones Kashmir y Dayan por esta experiencia única en la vida!

Post by Anjolene Hunt



2018 Breeding Season Update: A Bird’s-eye view from inside the nest

Why do birds arrive at different times on their breeding grounds, and why are there differences in when they lay eggs, and in when those eggs hatch? Is the timing of these events genetically hardwired or are these behaviors driven by the variation in environmental conditions these birds face?

To untangle the environmental and genetic factors affecting American Kestrel phenology (the timing of life cycle events), we monitored American Kestrel presence and breeding activity in nest boxes across the United States. These 246 nest boxes across 12 Department of Defense (DoD) sites encompassed a wide geographic area where vastly different environmental conditions and genetically distinct sub-populations likely occur (Read our fall blog post to see the variety of habitats across nest box sites).

To uncover what was going on inside the nest boxes, we used a combination of in-person visits (where biologists peeked inside nest boxes to see nest contents), and remote monitoring using trail cameras in nest boxes to capture time lapse images of nest contents.

Preliminary review shows that kestrels used >40 nest boxes across eight DoD sites in the 2018 breeding season.

Map of DoD sites where nest boxes have been installed: Yakima Training Center, WA; Camp Pendleton, CA; White Sands Missile Range, NM; Fort Hood, TX; Fort Riley, KS; Eglin AFB, FL; Big Oaks National Wildlife Refuge, IN; Fort Bragg, NC; Fort Drum; NY and two sites with pre-existing nest boxes: Dugway Proving Ground, UT; and Lucky Peak; ID. Orange bird symbols represent sites where American Kestrels were present in at least one nest box in 2018. Brown house symbols represent sites where no American Kestrels were present in nest boxes.

From trail cam photos and in-person visits, we collected timing information such as: the date kestrels arrived in nestboxes, when they laid eggs, when eggs hatched, and when nestlings fledged out of the nest box.

Using real-time information from cellular cameras and from communication with DoD biologists, our BSU crew conducted trips to DoD sites with nest boxes occupied by American Kestrels. We captured adult and nestling kestrels to attach unique identifying bands, take measurements, and collect genetic samples (from feathers) and isotopic samples (from claw clippings).

From April to mid-July 2018, our BSU crew banded, measured, and took samples from ~50 American Kestrels on the breeding grounds across six DoD sites (Fort Wainwright, AK; White Sands Missile Range, NM; Camp Pendleton, CA; Yakima Training Center, WA; Fort Bragg, NC; and Fort Riley, KS). DoD biologists at Lucky Peak, Idaho and Dugway Proving Ground, Utah independently captured and sampled an additional >20 kestrels. These samples will be used to help build the American Kestrel Genoscape, and to determine which individuals remained on the breeding grounds during the winter season (residents), and which individuals ventured south (migrants).

In addition to our kestrel breeding phenology data, our nest box monitoring efforts provided all kinds of fascinating data on predation, egg infertility and abandonment, and other species’ nesting phenology. Species using nest boxes ranged from starlings to flycatchers to owls; to squirrels and hungry snakes snacking on nestling birds; to infestations of wasps, ants, and kissing bugs. Although we were grateful that nest boxes provided easy hands-on access to breeding kestrels, we soon realized that they also provided refuge for many species that you’d rather not get your hands on!


From top left to bottom right: Rat snake in Eglin AFB, FL nest box; gopher snake in Camp Pendleton, CA nest box; European Starling in Yakima, WA nest box; Tufted Titmouse feeding nestlings in Fort Bragg, NC nest box; Eastern Bluebird feeding nestlings in Fort Hood, TX nest box; Western Screech Owl brooding nestlings in Fort Hood, TX nest box; Great-crested Flycatcher incubating eggs in Eglin AFB, FL nest box; Red Squirrels nesting in Fort Drum, NY nest box; flying squirrel in Fort Bragg, NC nest box.

In summary, the first breeding season of the Full Cycle Phenology project has been an unbelievable success and a major learning experience! Despite dealing with frustrating camera failures, nest predation, major insect infestations, and extreme weather events on DoD sites, we have made huge strides towards better understanding the variation in kestrel breeding phenology.

Stay tuned for more updates on our research as we head into fall migration season!

Time lapse video of American Kestrel nest in Yakima Training Center, Washington (video credit: Katie Callery)

This research is supported by the U.S. Department of Defense, through the Strategic Environmental Research and Development Program (SERDP RC-2702).

Special thanks to the 19 DoD biologists and volunteers across 12 DoD sites who monitored nest boxes and provided invaluable on-the-ground help with logistics, camera troubleshooting, and species identification.

Post by-Anjolene Hunt


Winter Update: sampling American Kestrels across their U.S. wintering range

While our genetics team at UCLA dons lab coats to analyze American Kestrel breeding feather samples and create a genoscape, the rest of our Full Cycle crew has been collecting feathers from kestrels across their U.S. wintering range. By matching the genetic signature of these wintering kestrel feathers to the markers identified from breeding kestrel feathers, we hope to be able to map individuals back to their breeding population of origin and to assess migratory connectivity.

Our first season of winter trapping was a huge success! Our crew collected feather samples from 191 kestrels from 15 states across 3 migratory flyways. We also had collaborators who contributed feathers in Oregon, Arizona, Texas, Utah, and Virginia. We sampled kestrels in agricultural fields, along forest edges, inter-mountain calderas, desert regions, and on coastal beaches across the country.


Map showing the locations that our Full Cycle Phenology crew (red dots) and collaborators (blue dots) sampled feathers from wintering American Kestrels from November 2017-February 2018

We have learned so much in this first year about conducting research across a vast geographic area, and about how much kestrels appear to vary across their wintering range in size, plumage, diet, and habitat associations. It will be so interesting to find out how genetic differences of individuals and the conditions they face in these highly diverse environments affect migration strategy and timing of life cycle events.

Whereas during the breeding season, kestrels using nest boxes are easy to find and hand-capture inside the box, things are a bit trickier during the winter season. Birds may be less tied to a specific area, and they have to be captured using other methods. We used winter Ebird locations (where other birders have seen kestrels) in combination with Google Earth imagery to hone in on the habitat that kestrels are typically associated with, and create rough maps of potential kestrel sampling routes.

When on the ground, we scanned along trees and power lines for perching kestrels. When we spotted one close enough, but not so close as to frighten them off, we placed a Bal-Chatri trap to lure kestrels in. Once kestrels’ legs were caught in the fishing line loops of the traps, we quickly ran over to collect them up for processing.


A pair of kestrels perches on a power pole (left), a female kestrel flies in towards a Bal-chatri trap (center), a male kestrel stands on a trap, likely caught (right). Photo credit: Jesse Watson

We took measurements of each kestrel (e.g. wing length, weight, fat score), attached a uniquely numbered USGS leg band, took photographs for plumage comparisons, and took a few breast/belly feathers for genetic analyses before releasing the bird.


Photographs are taken of this striking male’s back and wing plumage (left), a feather is sampled from a female kestrel (center), view of detached contour feather (right)

Our first trip to the Gulf Coast began with a rare December snowstorm in Louisiana. This was delightful for some locals making their first snowmen, but made for terrible weather to find and capture birds. Luckily, it only lasted a few days. The rest of our trip  was filled with kestrels and beautiful scenery. Mississippi and Alabama were prime kestrel areas with lots of wide open cropland and low-use dirt roads. We even recaptured a kestrel in Mississippi that had been banded in Maine in 2016!


A group of turkey vultures cleans a roadkill armadillo in Mississippi (top left), a short break in the rain and snow allows us to catch this male kestrel in Louisiana (bottom left), this recaptured female wintering in Mississippi was originally banded in Maine in 2016 (center), a cotton field provides hunting grounds for this female kestrel in Alabama (right)

The Florida Keys, although beautiful, were so heavily developed and highly trafficked that it was difficult to safely set a trap, while the less developed areas of the Keys were all off-limits federal or state protected land. However, we did manage to catch kestrels near some urban green spaces like marinas and golf courses, and on some of the less inhabited Keys.


 A female kestrel caught along a water-lined dirt road in the Florida Keys spreads her wings (top left), one of the many alligators basking near our trapping routes (bottom left), Anjolene holds a male kestrel caught at a forest-cropland edge in the Florida panhandle (center), Jesse displays a male kestrel caught beside a marina (right)

While one crew drove the Gulf Coast, our second crew headed into the Corn Belt in the Midwest (Kansas, Nebraska, and Oklahoma). Kestrels in these wide open and sparsely populated areas seemed to be wary of people, likely not used to seeing anyone down the dirt roads where they perch.  They must have had a good prey supply of corn-fed rodents, because these kestrels were the heaviest we caught all season!


Aislinn and Casey hold kestrels caught near a wind farm and a copse of trees in Oklahoma

With the east coast experiencing some of the coldest weeks in history, kestrel sampling was tough and chilly work in Georgia and North Carolina. Kestrels were rarely seen, likely huddled up in trees and structures to stay warm. With perseverance and warm vests, our crew managed to capture kestrels in both states, catching their first bird outside of a peanut factory. They also recaptured a female wintering in North Carolina, that had been banded as a nestling in Massachusetts 3 years prior!


Casey holds a female kestrel found hunting in wet fields in North Carolina (left), Aislinn releases a male on an unusually chilly day in Georgia (right)

The Imperial Valley in California had some of the highest densities of kestrels our team had ever seen! A kestrel on every second power line pole, and empty dirt roads made for prime kestrel trapping. We were lucky to have some fantastic collaborators who have worked in this area for years, to show us all of the best spots. Our team got to see where 2/3 of our winter produce is grown, and were excited to catch a kestrel beside an Aloe field.


An aloe field in California provides hunting grounds for kestrels (left), and Jay holds a lightweight female kestrel in Arizona (right) 

In Washington, kestrels were plentiful in areas lined with orchards and vineyards. The team came frustratingly close to catching one beside the aptly-named Kestrel Vintners winery, but were rewarded when they recaptured another female only 10 miles from where she had been banded 4 years prior!


Aislinn and Casey hold a male-female pair in Washington (left), and a female kestrel exhibits strikingly dark plumage

New Mexico was dry and hot, and we had to watch our traps carefully to make sure other raptors (and roadrunners!) didn’t get caught. We caught several female-male kestrel pairs who had no quandaries coming down on a trap after seeing their mate caught. It will be interesting to find out if these birds are year-round residents, or whether they are migrants that have paired up before the breeding season.


A Greater Roadrunner (left) demonstrates its camoflauge abilities in the dry New Mexico fields (photo credit: Anjolene Hunt), a Harris’ hawk scopes the surroundings from a power-pole perch (top right; Photo credit-Jesse Watson), Anjolene and Jesse hold a pair of kestrels caught on the same trap (bottom right)

In Texas, kestrels were not only inland in agricultural areas, but in open wooded areas, and even along the beach near Padre Island! Along with feather sampling of our Texas kestrels, we deployed GPS satellite transmitters on three females. Our transmitters send location data remotely, so we can determine exactly where kestrels migrate and breed, and use this information to validate our genetic methods. Read more about this aspect of the project on the HawkWatch International blog.


Jesse releases a kestrel on the beach near Padre Island, Texas (top left), this large female displays her newly attached GPS satellite transmitter (bottom left), this kestrel shares an open wooded area with cows and horses (right)

As the southern resident kestrels start getting ready to breed, and the migratory kestrels head back to breed up north, our winter season draws to a close. Stay tuned as we head into the breeding season and start our nest box camera project across U.S. Department of Defense installations!


Post by Anjolene Hunt


Fall update: Nest boxes across the nation

Almost everyone is familiar with American Kestrels, even if they don’t know them by name. In the spring and summer, these flashy falcons are found in abundance: sitting atop trees, telephone poles, and fence posts across North America.


Pictured above: A particularly spotty male American Kestrel in the Florida keys perched on a distribution pole
(photo credit: Jesse Watson)

Because the geographic range of this species is so vast, individuals living in different areas (e.g. Alaska vs. Florida) face different environmental conditions and may even be genetically distinct! These differences can affect timing of breeding and migration. For example, kestrels in Alaska will breed later and will migrate south in the fall, whereas kestrels in Florida will breed earlier and remain Florida residents over winter. With changing climate, timing of breeding and migration may be shifting, and the magnitude of this shift may vary for birds in different areas!


American Kestrels are cavity-nesters that are known to use to artificial nest boxes, and this method makes for easy monitoring of breeding populations. So to begin assessing the genetic and environmental factors affecting the timing of kestrel breeding and migration, we set up a large-scale nest box study on Department of Defense sites across the United States.

Starting with our northernmost site in Alaska, we shipped our pre-made pine nest boxes to our site, and hopped on a plane to meet them there. Next, we headed to New York, Indiana, Kansas, North Carolina, Florida, Texas, Washington, New Mexico, and California to drill nest boxes onto trees, power poles, and other elevated structures.

Pictured above: Nest boxes await shipping in a storage locker; Aislinn displays 20 bird boxes shipped to our Florida site; and Rich, Anjolene, Aislinn, and Casey post nest boxes on sites in Indiana, Alaska, Florida, and Washington.

We saw habitat from boreal forest, to long-leaf pine, to corn-fields, coastal wetland, and arid deserts, and wildlife like alligators, roadrunners, and moose. It was amazing to think about how kestrels are found in such diverse and interesting places!

Row 1 (left to right): Alaska, New York, Kansas, Indiana, North Carolina
Row 2: Florida, Texas, Washington, California, New Mexico

Along with beautiful views, each site brought with it a different set of challenges. From muddy, slippery driving and flat tires in Alaska, to bark-too-thick-to-drill-into in North Carolina, gnarled and crooked trees in Texas and Washington, to a lack of trees all together in New Mexico. Luckily for our team we had tremendous support from our Department of Defense (DoD) partners. Project co-investigator and DoD research biologist Richard Fischer facilitated communication with partners across sites, and he and fellow DoD biologist Jacob Jung met up with us on our travels to post boxes in Indiana and Kansas. We also partnered with a number of exceptional DoD biologists on each site who provided the on-the-ground knowledge, logistical help, tools, and human-power needed to get our nest boxes posted.


In fall 2017 our team posted 200 nest boxes within Department of Defense installations in 10 states, in addition to two states which had pre-existing nest box programs. And with that we wait…. to see if kestrels across the U.S. take to their new homes, and become part of a large-scale, full-annual study of their species.

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Above: A female American Kestrel in Idaho broods her newly hatched nestlings inside a nest box

Special thanks to our on-the-ground DoD partners:

Fort Wainwright, Alaska: Daniel Rees, Garrett Savory
Fort Drum, New York: Jeffrey Bolsinger
Big Oaks National Wildlife Refuge, Indiana: Joseph Robb
Fort Riley, Kansas: Shawn Stratton, Jeff Keating
Fort Bragg, North Carolina: Jessie Schillaci
Eglin AFB, Florida: Rodney Felix, Justin Johnson
Fort Hood, Texas: Amber Dankert, Jackelyn Ferrer-perez
Yakima Training Center, Washington: Colin Leingang, Jennifer Bader
Camp Pendleton, California: Bill Berry, Diane Walsh, Katrina Murbock, Sherri Sullivan
White Sands Missile Range, New Mexico: Patricia Cutler, Doug Burkett
Lucky Peak, Idaho: Keith Hyde
Dugway Proving Grounds, Utah: Robbie Knight



Breeding season wrap-up and call for winter feathers

The 2017 American Kestrel breeding season is well behind us, and the numbers are in! This breeding season, we received feather samples from 610 American Kestrels from across the breeding range!

Collaborators from 25 states sent us feathers from kestrels in their nest boxes, trapping sites, and rehabilitation facilities.

With the samples sent off to the genetics lab at University of California, Los Angeles for analyses, we are making great strides towards understanding the genetic structure of breeding kestrel populations.


This map shows locations where we have received feathers from American Kestrels in the breeding season (orange), migration season (yellow) and winter season (blue) from 2017 and prior years. (Not pictured: Alaska). We welcome samples from all locations, but if you work with kestrels in an areas without dots, WE NEED YOUR HELP! Please SIGN UP to contribute feathers, or see our GET INVOLVED page to find out more. 

Full annual cycle research does not slow down with the cooling temperatures, and with winter upon us, the next phase of the Full Cycle Phenology project is shaping up. By sampling kestrels during migration and overwintering, we hope to be able to map individuals back to their breeding population of origin and to assess migratory connectivity and WE NEED YOUR HELP!

If you work with wintering kestrels please consider contributing feather samples. If you aren’t on our list yet, please SIGN UP to get your sampling kit mailed to you. If you are already signed up, but need more sampling envelopes, please Contact Us .



Spring Update: American Kestrel Genoscape

The American Kestrel breeding season is well underway and kestrel researchers, citizen scientists, and wildlife rehabbers from across the U.S. and Canada have been diligently collecting feather samples to create the American Kestrel Genoscape.


It has been fantastic to connect with people working with kestrels across their breeding range, and we are excited to learn more about the different breeding populations from Alaska down to Florida, and from coast to coast across the continental U.S. and Canada! In 2017, we have had 28 feather contributers sign up from 16 states, and 5 Canadian provinces, bringing our total sampling area to 24 states, and 5 provinces from 2016-2017 (see map below).

Although we have had a great show of support and feather sample contributers, we are still in need of feather samples, particularly from the Midwest (see map below). If you work with kestrels in this area, please SIGN UP to contribute feather samples. We have little information about kestrels in this region, which may use different migratory flyways and wintering locations than eastern or western populations.

This map shows locations where we have feather sample contributers (2016: blue dots, 2017: orange dots).
We welcome samples from all locations, but if you work with kestrels in an areas without dots, WE NEED YOUR HELP! Please SIGN UP to contribute feathers, or see our GET INVOLVED page to find out more.