U.S. Fish & Wildlife Service

Sacramento Fish & Wildlife OfficeServing the people, conserving the fish, wildlife, and plants of California

A Unit Of The Pacific Southwest Region

Site Visit Insights from Harry Kahler

Aug 1, 2018

1 / 17
Photo of Harry Kahler
Harry Kahler is a fish and wildlife biologist in the Sacramento Fish and Wildlife Office. Photo credit: Veronica Davison, USFWS.
2 / 17
Photo of nest box mounted in the tree
U.S. Fish and Wildlife Service staff built nest boxes for American Kestrels to lay eggs. Photo credit: Veronica Davison, USFWS.
3 / 17
Photo of 5 eggs in nesting box
American Kestrels typically lay between 4 and 5 eggs, but can lay anywhere from 2 to 7 eggs. Photo credit: Veronica Davison, USFWS.
4 / 17
Photo of Harry Kahler and Doug Weinrich removing chicks from the nesting box
Fish and Wildlife Biologist Harry Kahler gets help from Assistant Field Supervisor Doug Weinrich as he carefully removes the chicks from the nesting box one-by-one and transfers them into a soft bag Weinrich is holding. Photo credit: Veronica Davison, USFWS.
5 / 17
Photo of insects on baby chick
Nesting boxes keep chicks safe from predators, but mites, ants, and other insects can still get in. Photo credit: Veronica Davison, USFWS.
6 / 17
Photo of bird being banded by Biologist Harry Kahler
Fish and Wildlife Biologist Harry Kahler bands a nine-day-old kestrel, which can help identify the bird at a future encounter. Photo credit: Veronica Davison, USFWS.
7 / 17
Photo of American kestrels' in a nesting box
Females can lay two broods in one season if the first group of eggs it laid is early. Photo credit: Veronica Davison, USFWS.
8 / 17
Photo of service employes working
L to R: Service employees Jennifer Brown and Harry Kahler record data on recently hatched American Kestrels with California Department of Fish and Wildlife colleague Carie Batttistone. Photo credit: Veronica Davison, USFWS.
9 / 17
Photo of Tree with a nesting box and a desceased female on the ground
It is not always clear why eggs do not hatch. In this case, the female was found deceased right under the nesting box. Photo credit: Veronica Davison, USFWS.
10 / 17
Photo of Female/Male comparison
American kestrels’ striking looks include slate-blue wings and heads on males, and a pair of black stripes on each cheek in both males and females, sometimes referred to as their mustaches and sideburns. Photo credit: Veronica Davison, USFWS.
11 / 17
Photo of American Kestrel being held in persons hand
American Kestrels are born with talons and a beak that will be put to the test within a couple of months when they begin catching voles, mice, and other critters—it takes several months before they are fully independent. Photo credit: Veronica Davison, USFWS.
12 / 17
Photo of bird band affixed to bird
The metal bird bands are affixed through a painless process of using a tool especially made for banding that prevents the band from fitting too tightly around the bird’s leg. Photo credit: Veronica Davison, USFWS.
13 / 17
Photo of American kestrel showing wingspan
American kestrels are about the same size as mourning doves, with a broader wingspan and a much fiercer nature. Photo credit: Veronica Davison, USFWS.
14 / 17
Photo of tree suitable for breeding season
During the breeding season, kestrels require open woodlands or grasslands for foraging, with suitable tree cavities or fabricated wooden boxes for nesting. Photo credit: Veronica Davison, USFWS.
15 / 17
Photo of nine day old American Kestrel
Nine-day-old American kestrel. Photo credit: Veronica Davison, USFWS.
16 / 17
Photo of 28 day old American Kestrel
Twenty one-day-old American kestrel. Photo credit: Veronica Davison, USFWS.
17 / 17
Photo of 28 day old American kestrel
Twenty eight-day-old American kestrel. Photo credit: Veronica Davison, USFWS.

Site visits are critical to helping Sacramento Fish and Wildlife Office (SFWO) biologists learn more about species and their habitats. The trips often take them into areas most people do not have a chance to explore, including public and privately-owned restricted sites, as well as some remote and hard-to-reach areas. “Site visit Insights” provides a behind-the-scenes perspective of wildlife biology, featuring photographs and interesting discoveries and happenings SFWO biologists experience in the field.

Wildlife Biologists: Harry Kahler, fish and wildlife biologist, Sacramento Fish and Wildlife Office

Site visit location: Beale Air Force Base, California

What was the purpose of the site visit?
The purpose of this site visit was to band and collect information about American kestrel nestlings. Nesting sites for American kestrels are limited. As part of The Peregrine Fund’s American Kestrel Partnership, the Sacramento Fish and Wildlife Office installed a series of kestrel nest boxes at various sites on Beale Air Force Base. We monitor them for use and productivity during the breeding season each spring. We collect basic information about the eggs and nestlings we find at each location and fit the nestlings with metal bands for future identification. Along with other data collected throughout the range of the kestrel, our nest box information will help provide clues as to why American kestrel populations are declining.

The American kestrel (Falco sparverius) is not on the endangered species list, but it is protected by the Migratory Bird Treaty Act. It is the smallest falcon found throughout the Americas. Since scientists began collecting breeding bird survey data in the 1960's, population declines of American kestrels have been reported across the species range. Although the cause of the decline is not clear, loss of adequate breeding habitat is one potential explanation.

During the breeding season, kestrels require open woodlands or grasslands for foraging, with suitable tree cavities for nesting. They are tolerant of most human activities and will readily nest in manmade boxes when cavities are not available. Nesting sites that are relatively free from human disturbance are more successful at producing fledglings. Where possible, our boxes were placed in areas without frequent human activity, and away from areas that may interfere with the base’s military operations.

Where did you go?
Beale Air Force Base in Yuba County, California. The base serves as excellent habitat for wildlife and is home to critters of all types—from snakes and fish to birds and mountain lions.

What partners were you working with and what is the nature of SFWO’s partnership with them?
We partner with representatives from the California Department of Fish and Wildlife and Beale Air Force Base. Without our partners, this project wouldn’t be possible.

We work closely with representatives from Beale Air Force Base to ensure that the nest boxes are placed in areas that won’t interfere with critical missions of the base. As part of the Sikes Act, the Service partners with the military nationwide to ensure that about 25 million acres of land containing military installations can support ecosystems while fulfilling military obligations. The land is largely protected from development.

To monitor the boxes, document observations, and band the nestlings, we work with the California Department of Fish and Wildlife.

What did you learn from this site visit that you didn’t know before?
Our nest boxes were installed in a variety of places: some hilly, some flat, some remote, and some closer to buildings. Not all boxes placed in areas that looked highly suitable to the human eye were used by the kestrels, while other boxes placed in areas that seemed less adequate were selected by the birds.

The average clutch size, or number of eggs laid in a breeding attempt, is 4 to 5 eggs. This year we observed several clutch sizes of 6 or 7 eggs. Also, raising a full brood of 5 chicks or more to fledging requires plentiful food resources. Although our data are limited, these larger clutch sizes and fledgling success may indicate that Beale Air Force Base provides excellent habitat for American kestrels.

In all, nest box selection and nesting success varies from year to year. It’s an important reminder that relationships between wildlife and habitats are multi-faceted and complex. The data we collect each year is compiled with information from other studies across the entire population range of the American kestrel to help us better understand the relationship between wildlife and habitat for this species.

What surprises did you encounter during the site visit?
It’s not easy to be an American kestrel. Nest boxes can be chilly or very hot, and invariably they are also inhabited by ants and other crawling insects. Even chicks that were just a few days old already had mites covering them. In other cases, some eggs didn't even get that far along, as we found evidence of a mother kestrel being preyed upon before her eggs hatched. Unfortunately, without her to keep them warm, her eggs did not hatch.

They’re born with talons and a beak that comes into play very early. Handling nestlings that are just 7-10 days old, for example, can seem like trying to get ahold of a contorting pin cushion! By the time they leave the nest after about a month, they are fully capable capturing prey. Seeing these struggles firsthand fully demonstrates the challenges and beauty of our successful conservation efforts.

Learn more about American Kestrels

Last updated: August 1, 2018