I am glad that it has warmed up and that it is time to band kestrels! Thirty volunteers for Madison Audubon’s Kestrel Nestbox Monitoring Program were busy in March cleaning out kestrel boxes, and we’re now seeing the results of their work. This nestbox program has two primary goals: 1) provide clean, abundant nest sites for kestrels to raise their young, and 2) create opportunities to band both adults and chicks to study their migration patterns, demographics, nesting preferences, and more.
Once kestrels arrive back in Wisconsin in late March and April, the monitors start checking theirs boxes with a remote camera device. This is done every week to 10 days over the breeding season to see how the nesting season is going, and at the end of the season we report our results to the American Kestrel Partnership.
The program has 171 nestboxes up and available to these birds, though they’re never all in use by kestrels. Of our 171 boxes, 50 are in use by kestrels over an eight-county area in 2019. Many of the boxes are located in south-central Columbia County, especially around Goose Pond Sanctuary. Other species including eastern bluebirds, tree swallows, house wrens, and even screech owls use the nestboxes. And of course, starlings and house sparrows, though those nests are cleaned out to prevent the spread of those exotic invasive species.
Feeding into the program’s goal of banding kestrels, we work with Janet Eschenbauch and her daughter-in-law Amber Eschenbauch from Central Wisconsin Kestrel Research, who come from the Stevens Point area to conduct the banding. Janet and Amber have been banding kestrels at the Buena Vista Grasslands for the last 19 years, and have assisted us with banding our local kestrels for the last 3. Their team has banded 2,000 kestrels -- they really are pros!
By checking nest boxes, we can determine whether and when the adult kestrels are incubating eggs. The incubation period is the best time to capture adults for banding because there is an adult always in the nest. We use the best methods and techniques to quickly and efficiently band the birds and return them to the nest, and as a result the disruption and stress to the birds and eggs is negligible.
Our team of volunteers help Janet and Amber by getting the ladder in place, banding and recording data. The convoy stops short of the active box and Janet quietly approaches the nest box, carrying her long-handled net. The net is like a fish landing net, but the netting has been replaced with bird friendly mist net material. Once Janet has the net placed in front of the hole the ladder crew places the ladder next to the house. A volunteer holds the net in place and Janet climbs the ladder and look into the nest box.
Then, one of two things happens. Most times, the kestrel flushes and flyes into the net so we can safely bring it down to the ground. Sometimes the adult stays in th the box and Janet then reaches in and gently grabs the bird.
When the bird flushes into the net, it is cradled there and this is where Amber shows her expertise with the birds. You would be amazed at her patience and skill in order to unwrap the netting from the bird. In fact, Amber and Janet have done this hundreds to thousands of times.
Once the bird is in hand they place a metal band (bracelet) with a distinct number on a leg. Once the band is on, they judge the the overall health of the kestrel by looking at the fat reserves under the feathers on the bird’s armpit and weight of the bird. The females tend to weigh more than the males due to her sitting on the eggs and the male bringing food to her. Next they count and check the wing and tail feathers to determine if the bird is molting.
Next comes the most interesting part of the capturing of the bird, as quoted by Janet and Amber in their newsletter. “We are excited to announce that we are providing Wisconsin kestrel feather and claw samples as part of a four-year, continent-wide study on American Kestrels to learn about the effects of climate change on the phenology (timing of life-cycle events) of American Kestrels. This study is led by Dr. Julie Heath of Boise State University and is in collaboration with HawkWatch International (HWI), UCLA, and The Peregrine Fund.”
Last year, more than 250 feather samples -- a tiny feather taken from the belly of the bird -- were collected from 16 locations. Of those, 48 samples were provided from Wisconsin kestrels as part of our project and their central Wisconsin project. Researchers will extract DNA from the skin cells at the tips of these feathers and assay the DNA using a genetic tool being developed for American Kestrels.The tool is called a single nucleotide polymorphism (SNP) panel, which can be used to distinguish between kestrel populations. Although still in the early data analyses stage, preliminary results suggest that the panel will be able to successfully distinguish between kestrels in different parts of their range.
The claw (toenail) samples on adults -- a 0.5 millimeter clipping from one claw -- are use to measure the ratio of hydrogen stable isotopes (hydrogen and deuterium). The ratio of the 2 hydrogen isotopes varies with latitude, so we should be able to determine where a kestrel grew its claw. Claw tissue turns over about every 4-6 months, so samples collected in the spring should reveal the hydrogen isotope signature of where the bird spent the winter.
We did have some surprises this spring while banding adults. Of the 23 boxes checked, four contained chicks. The chicks ranged from 2 to 16 days old. The 16-day old chicks are some of the oldest chicks we have encountered at this time of year. It takes 30 days for kestrel eggs to hatch and the first egg for this clutch was laid on April 5.
One box has been lost due to predation, most likely a racoon. This is not a common occurrence but does happen. For this reason we place metal sheeting on the top section of the nest structure pole, which has shown dramatic reductions in nest predation. But even that isn’t a 100% perfect solution when up against a hungry, determined racoon.
In the other 20 boxes, four adult males and 20 adult females were caught. About 25% of the time the male incubates while the female goes hunting. If a male is caught the crew returns later that day or the next day to capture the female. One male was caught twice but the third time we caught the female!
We also found one female with a badly swollen foot. This could have occurred from a hair or monofilament line becoming entangled around the foot or toe, or a snake or spider bite. We have been in contact with Marge Gibson, a licensed rehabilitator who is the head of the Raptor Education Research Group, Inc (REGI) and the Dane County Humane Society’s Wildlife Center to help us decide if we should intervene. Janet is concerned that the female may have problems perching. Thanks to Graham Steinhauer and summer intern Tanner Pettit for placing dead, day-old pheasant chicks from the DNR Game Farm in the box every other day to help the female maintain her weight. We will be providing more information on this bird as the season advances.
Next, we are looking forward to banding chicks around mid-June. If you want to be involved with chick banding watch the Madison Audubon website for registration announcements. This is a very informative and fun activity. It is likely you will be able to hold a kestrel chick and have a photo taken! Many people have a new favorite bird after helping band kestrels.
Special thanks to Janet and Amber and our kestrel volunteers.
Written by Brand Smith, MAS American Kestrel Nestbox Program coordinator, and Brenna Marsicek, director of communications
Cover photo by Jim Stewart