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American Kestrel (Falco sparverius) Attacks Red-cockaded Woodpecker (Picoides borealis) Fledgling
Jessica Schillaci

Southeastern Naturalist, Volume 10, Issue 2 (2011): 378–380

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378 Southeastern Naturalist Vol. 10, No. 2 American Kestrel (Falco sparverius) Attacks Red-cockaded Woodpecker (Picoides borealis) Fledgling Jessica Schillaci* Abstract- A Falco sparverius (American Kestrel) was observed attacking and carrying away a Picoides borealis (Red-cockaded Woodpecker) fledgling during observations associated with a long-term monitoring program on Fort Bragg Military Installation, Fort Bragg, NC. The woodpecker was released in mid-air approximately 100 m from the site of the attack and fell to the ground, alive. It is unknown if the American kestrel returned to consume the fledgling, or if the fledgling survived the encounter. Picoides borealis (Vieillot) (Red-cockaded Woodpecker; hereafter RCWO) is a primary cavity nester of the Pinus palustris P. Mill (Longleaf Pine) ecosystem and the only woodpecker in North America to construct its cavities in living pine trees. The RCWO’s cavity excavations in living pines provide a resource for numerous secondary cavitynesting species (Blanc and Walters 2008). Populations of the endangered RCWO have been studied and monitored for 3 decades in this ecosystem (Britcher and Patten 2004, Brust et al. 2004, Carter et al. 1983), and the members of this species commonly raise broods in cavities located in the same pine tree with secondary cavity nesters, including avian predators such as Otus asio L. (Eastern Screech Owl) and Falco sparverius L. (American Kestrel), which nest in enlarged RCWO cavities (Blanc and Walters 2008, Gault et al. 2004, Hoffman and Callopy 1987). The American kestrel is a small (97–150 g), sexually dimorphic falcon, which occurs throughout the Americas. It can be considered an opportunistic-generalist (Callopy and Koplin 1995), consuming insects, lizards, small rodents, and birds, depending on temporal variability (Sarasola et al. 2003), energetic requirements during the breeding season (Bohall 1984), and location (Rojas and Stappung 2004). The RCWO (42–52 g) falls within the weight range of avian prey items (16–300 g) reported for American Kestrels (Rojas and Stappung 2004); however, small lizards comprise the majority of vertebrate prey consumed during the breeding season in open woodland habitat types (Smallwood 1990) like those on Fort Bragg. Alarm calls given by the RCWO when a kestrel is visible infer a predatory relationship (Buchanan 1989); however both species raise broods concurrently in nesting densities up to 4 pairs per square kilometer in the Longleaf Pine ecosystem (Gault et al. 2004), and there are no previous records of an American Kestrel preying on a RCWO. The Fort Bragg Military Installation (FB) is located in the Sandhills region of southcentral North Carolina, an area characterized by second-growth Longleaf Pine forests previously described in detail by Carter et al. (1983). The site where the incident occurred is located on the Overhills tract in the northeastern portion of FB. It is managed with growing-season burns every 1–3 years in order to maintain an open midstory and diverse groundcover dominated by Aristida stricta Michx. (Wiregrass). At approximately 0830 on 20 June 2008 during routine RCWO-monitoring activities at Cluster 470, we observed two 26-day-old color-banded fledglings. The 2 were vocalizing and fighting with each other on a limb in the crown of a mature Longleaf Pine. One of the fledglings was identified as a male because of his red crown patch, but we had not *Directorate of Public Works, IMSE-BRG-PWE-E, 2175 Reilly Road Stop A, Fort Bragg, NC 28310-5000; Jessie.schillaci@us.army.mil. 378 Notes of the Southeastern Nat u ral ist, Issue 10/2, 2011 2011 Southeastern Naturalist Notes 379 determined the sex of the other fledgling. The adults (a breeding pair and 2 helper males) were nearby and intermittently called and fed each of the fledglings. The squabbling continued as the fledgling of unknown sex was repeatedly pecked and chased around the bole of the pine tree by the male fledgling. The former flew to a large horizontal limb to escape harassment, then moved to a smaller limb where it had a difficult time becoming situated. At this time, an adult RCWO issued an alarm call and the other adult RCWOs stopped vocalizing. An American Kestrel flew into the site, plucked the fledgling bird from the limb, and flew off in a southwesterly direction. The captured fledgling began a loud, raucous calling which continued as it was carried away. We observed the direction the Kestrel flew carrying the fledgling and followed it to determine the fledgling’s fate. At this time, we heard and identified several Kestrel fledglings in the area. Approximately 100 m from the site of the attack, the Kestrel dropped the RCWO to the ground and flew off. Due to the brownish plumage and call of the kestrel, we believe it was an adult female. The RCWO fledgling was alive on the ground, but appeared unable to fly, and was identified as a female. We did not touch the bird and left the area. We returned several hours later and found no evidence of the injured RCWO. The fledgling’s fate is unknown as she was not seen in the FB population again. Her brother of the same brood was present at his natal cluster in the 2009 breeding season. It is well known among falconers that abnormal prey behavior is attractive to predatory birds, as certain trapping techniques use distressed, harnessed pigeons or freemoving mice and gerbils as bait. It has also been shown that kestrels and other falcons select prey based on their activity level (Sarno and Gubanich 1995, Smallwood 1981), rather than just body size (Bryan 1984, Smallwood 1989), and that the selection of small to medium-sized (16–80 g) prey items could be influenced by high energy requirements during the nesting season (Collopy and Koplin 1983, Sarasola et al. 2003). Additional factors such as degree of hunger (Bryan 1984), temporal differences (Bohall-Wood and Collopy 1986, Smallwood 1987), search image (Tinbergen 1960), and territory quality (Smallwood 1987) may also influence prey-size selection and the relative representation of such items in the diet (Collopy and Koplin 1983). The considerable amount of commotion associated with the circumstances leading up to the attack support the idea that American Kestrels are opportunistic and will expand their typical prey selection during times of increased energetic demands (such as the post-fledging period), particularly when a prey item is both conspicuous and vulnerable. Acknowledgments. Special thanks to Brian Ball, Jacqueline Britcher, Dr. Jay H. Carter III, and other, anonymous reviewers of this manuscript. Literature Cited Blanc, L.A., and J.R. Walters. 2008. Cavity excavation and enlargement as mechanisms for interactions in an avian community. Ecology 89:506–514. Bohall, P.G. 1984. Habitat selection, seasonal abundance, and foraging ecology of American Kestrel subspecies in north Florida. MS Thesis. University of Florida, Gainesville, FL. 97 pp. Bohall-Wood, P., and M.W. Collopy. 1986. Abundance and habitat selection of 2 American Kestrel subspecies in north-central Florida. Auk 103(3):557–563. 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