Abstract
Complex coevolutionary relationships among competitors, predators, and prey have shaped taxa diversity, life history strategies, and even the avian migratory patterns we see today. Consequently, accurate documentation of prey selection is often critical for understanding these ecological and evolutionary processes. Conventional diet study methods lack the ability to document the diet of inconspicuous or difficult‐to‐study predators, such as those with large home ranges and those that move vast distances over short amounts of time, leaving gaps in our knowledge of trophic interactions in many systems. Migratory raptors represent one such group of predators where detailed diet studies have been logistically challenging. To address knowledge gaps in the foraging ecology of migrant raptors and provide a broadly applicable tool for the study of enigmatic predators, we developed a minimally invasive method to collect dietary information by swabbing beaks and talons of raptors to collect trace prey DNA. Using previously published COI primers, we were able to isolate and reference gene sequences in an open‐access barcode database to identify prey to species. This method creates a novel avenue to use trace molecular evidence to study prey selection of migrating raptors and will ultimately lead to a better understanding of raptor migration ecology. In addition, this technique has broad applicability and can be used with any wildlife species where even trace amounts of prey debris remain on the exterior of the predator after feeding.
Highlights
Foraging ecology and predator–prey interactions have shaped the natural histories of species, including distribution and abundance as well as complex behaviors such as foraging strategies, inter‐ species competition, and timing and route of migration (Abrams, 2000; Alerstam, Hedenström, & Åkesson, 2003)
We successfully developed and tested a minimally invasive tool to document the diet of migrant raptors, and other enigmatic preda‐ tors, by swabbing beaks and talons
We demonstrated that prey DNA can successfully be collected and identified from the exterior of a predator even when a recent feeding was not evident and visible prey remains were not present
Summary
Foraging ecology and predator–prey interactions have shaped the natural histories of species, including distribution and abundance as well as complex behaviors such as foraging strategies, inter‐ species competition, and timing and route of migration (Abrams, 2000; Alerstam, Hedenström, & Åkesson, 2003). DNA metabarcoding has been a revolutionary tool in studying the diet of many wildlife species utilizing fecal or gut samples (Clare, 2014; Kress, García‐ Robledo, Uriarte, & Erickson, 2015; Pompanon et al, 2012), but has yet to be implemented for raptor diet studies or by sampling the ex‐ terior of a predator's mouth and claws The benefit of this tool resides in the ability to document prey selection of wildlife when traditional methods are not possible and has the potential to be utilized for any wildlife species where even trace amounts of prey debris remain on the exterior of the predator after feeding, for example, vultures, piscivorous birds, insectivo‐ rous or predatory songbirds, and even nectarivores such as bats and hummingbirds, where trace plant DNA from pollen may be pres‐ ent (Nagarajan, Prabhu, Kamalakkannan, & Sinu, 2018). Our objectives are to (a) develop a minimally invasive method for use in studying the diet of predators using raptors as a case study; (b) verify that prey DNA can be success‐ fully obtained and identified from raptors with a known diet; and (c) apply our method to wild migrating raptors and identify prey to species
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