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Build a Kestrel Nest Box!

October 29, 2016 Category: Tags: , , , ,

We are hoping to dramatically grow our Kestrel Nest Box program. Program director Frank Nicoletti would like to eventually have a 100-box route, but would like to add at least 20 new boxes this winter.


Kestrels are declining nationwide, and the reasons are unclear. One big reason may be the increase of pesticide/herbicide use by agriculture. Another reason is the fact that Starlings can usurp natural nest cavities. Frank hopes to not only provide the Bog’s abundant Kestrels with more cavities to nest in, but also to band the nestlings to find out more about their site fidelity and migration patterns.

You can help us by building Kestrel nest boxes using our simple plans here.

**Use cedar instead of pine (last much longer in the field)
**Make a hinged lid (as shown in the plans) so Frank can access the nestlings and easily band them…Side-opening nest boxes allow the possibility that the nestlings will escape when he tries to band them.

Simply drop the completed boxes off at the Welcome Center…or if we aren’t around just leave it on the west side of the building. If you need a tax form so you can deduct your donation, just email us at info@saxzim.org.




In response to declining populations of American Kestrels in parts of their range (including northern Minnesota), Friends of Sax-Zim Bog put up 14 nest boxes in 2015. The boxes mimic kestrels natural nesting sites in tree cavities, providing suitable nesting sites for the population of kestrels that breed in the bog. The goal of the project is to gather data on nesting success, number of chicks hatched and fledged, and make notes on species competing for similar nesting sites. And, of course, to encourage kestrels to breed in the Sax-Zim Bog!

This year, 13 of the 14 original boxes were up for kestrels to nest in. One had fallen during spring and never put back up. Volunteers monitored the boxes during five monitoring periods to check if the boxes were occupied and to note any breeding behaviors observed. Monitors observed kestrels at or near nine boxes during the season and recorded copulation at four of the boxes. We also made notes on other species present, general kestrel behavior, and foraging. When observing one of the boxes, Eliza Grames watched the male kestrel leave the wire and hunt over an adjacent field, where he caught a snake and proceeded to eat it on the wire above the nest box.

Last year, three boxes were occupied by kestrels and two had starlings nesting in them. This year, seven boxes were occupied by kestrels and there was only one box with starlings! Occasionally, other kestrel nest box sites have had species like Northern Flickers, Great crested Flycatcher or even flying squirrels nesting in them, but there were none this year in the bog boxes.

The chicks were banded on July 6, 2016 by Frank Nicoletti, Miranda Durbin, Peter Yokel, and myself. We drove to each nest box, climbed the ladder to peer inside the box and see if there were young, and then carried the young out and down to the road to band them.

We arrived at the first box and prepared for “jumpers” (chicks old enough to try to jump out of the box when approached). Frank placed a t-shirt over the top of the bucket to keep chicks from escaping, and Peter was ready to cover the hole of the nest box when he got to the top of the ladder to prevent chicks from jumping. To our surprise, when Peter opened the box, he found two chicks that were still completely covered in white, fuzzy down feathers. They weren’t even old enough to determine the sex, which is based on plumage. Luckily, they were old enough to have fully formed legs, so we were able to band them. Each chick got a band from the Bird Banding Laboratory with a unique 9-digit number.

Another box had five chicks, all female, that were close to fledging and others had chicks that were partly downy but starting to grow flight feathers. The reason for the differences in ages is that some boxes likely failed the first time and the kestrel pair occupying the box tried over. We know this because kestrels typically lay 4-5 eggs the first time, and only 2-3 the second time because of the energy required to produce an egg, incubate the eggs, and raise young. This explains why the box with the female chicks that were close to fledging had five young, but the ones that were still downy and recently hatched only had 2-3 chicks per box. There are a number of reasons a box could fail the first time – we suspect predation or cold weather during the incubation period were probably the reasons for nest failure in the bog.

In all, we banded 21 chicks (12 females, 3 males, 6 unknown) from seven boxes. This bodes well for the future of kestrels in northern Minnesota. The boxes will be monitored again next year and we hope to increased the number of boxes to 50. So we’ll keep our fingers crossed to have even more chicks in 2017!

Thanks to Clinton Nienhaus for coordinating the monitoring and volunteers, Amy Johnson, Mary Gabrys, Sally Grames, and myself for monitoring the boxes, Frank Nicoletti, Miranda Durbin, Peter Yokel and myself for banding the chicks, and Sparky Stensaas for his work supporting the project through Friends of Sax-Zim Bog.

submitted by Eliza Grames and Frank Nicoletti

Kestrel nestlings ready to be banded. Photo by Miranda Durbin

Eliza Grames banding Kestrel chicks. Photo by Miranda Durbin