Examining Changes in Prey Biomass Delivery Throughout American Kestrel Nestling Development

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American kestrels (Falco sparverius) are declining throughout North America for reasons that are unknown due to a lack of information about their habitat preferences and diet. The Northern Virginia Piedmont Kestrel Project aims to address that by determining adult foraging habitat preferences and nestling diet composition through data from kestrel nest box video cameras and GPS monitoring. I processed nest box videos and recorded prey deliveries from the first three weeks of the four-week nestling period using previously developed protocols to examine the diet of kestrel nestlings. My objective was to determine how prey biomass delivery and prey delivery rates vary throughout kestrel nestling development, which had not been examined previously as part of this project. I used linear mixed models to analyze the effects of nestling age in weeks and days on biomass delivery (g/hr/nestling) and the effects of nestling age in weeks and days on delivery rate (deliveries/hr). I found that the delivery rate increased in later weeks of the nestling period but that there was no consistent change in biomass delivery. This showed that adults adjusted their prey delivery rate based on nestling age but may not have selected for larger prey items. This contributed to an understanding of how kestrel parents provided food to nestlings over the nestling period and provided information on important prey items for kestrel nestlings to be used in kestrel conservation. Further research is needed on how prey composition by biomass of different prey types changes over the nestling period.

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