American Kestrel Research Summary

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American Kestrel Research Summary

December 2, 2015

Adam Shreading of Rapture View Research shares a summary of Kestrel research on the MPG Ranch in 2015.

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American Kestrel Research Summary Raptor View Research Institute

This summer, we monitored American Kestrel nests on the MPG Ranch for the third consecutive year. Rather than attempt to survey the whole ranch, we focused our efforts at low elevations to the west of Mt. Baldy. We were able to survey this smaller area more thoroughly than in past years, and believe we located all nests in the area. We found 16 nests.

We found eight nests in natural cavities and eight in nest boxes. Compared to previous years, American Kestrels used fewer nest boxes along the main road. We suspect increased traffic along the roads made these sites less attractive to nesting kestrels. Tree Swallows used one nest box and European Starlings used eight nest boxes. Because they initiate nests earlier than American Kestrels, European Starlings prevent American Kestrels from using the nest boxes they occupy.

Twelve of 16 kestrel nests produced young this year (Table 1). We saw higher nest success in 2015 (75%) compared to 2014 (59%) or 2013 (63%). Similar to previous years, successful nests produced an average 3.83 young (SD=0.83), for a total of 46 fledglings.

We captured and banded 41 kestrels, including 14 breeding adults and 27 nestlings. We’ve captured 191 kestrels since 2011.

We encountered seven adult American Kestrels banded in previous years. To date, we have encountered 24 of 73 (33%) color banded adult American Kestrels in multiple breeding seasons. While a few individuals have used the same nests in multiple years, the majority of American Kestrels change nesting territories and mates each year.

We banded AK 47 on May 10, 2012 at his nest cavity, a large ponderosa pine snag above the northern floodplain. The following year he unsuccessfully nested with AK 85, who died while incubating. In 2014 he paired with an unbanded female, and fledged just two young from a nest box near the mouth of Tongue Creek. This year, he returned to his 2014 nest box where he failed to produce young with AK 162.

We captured AK 62 on July 8, 2012 at her nest box near the Top House. She fledged four young with an unbanded male. In 2013, she moved to a nest box in the Lower Woodchuck drainage, where she successfully fledged four young with an unbanded male. She returned to this same area in 2014, but used a natural cavity rather than the nest box. She reared four young with AK 117. This year, she switched back to the nest box from 2013, and raised four young with an unbanded male.

We captured AK 148 July 21, 2014 north of the duck pond, near a natural cavity where he fledged two young with an unbanded female. This year he fledged 2 young with an unbanded female from a different natural cavity near the Bald Eagle nest.

We captured AK 86 on May 24, 2013 near the south center pivot. We saw him perched in the same area numerous times during the past two summers, though we never documented him nesting. We believe he uses natural cavities off the MPG Ranch.

We deployed 14 PinPoint GPS units on adult American Kestrels breeding on MPG Ranch. We look forward to seeing these individuals next summer and learning where they spent the winter!