620 THE WILSON JOURNAL OF ORNITHOLOGY N Vol. 122, No. 3, September 2010

The Wilson Journal of Ornithology 122(3):620–622, 2010

Infanticide by an Eastern Phoebe

Gary Ritchison1,2 and Brandon T. Ritchison1

ABSTRACT.—We videotaped an Eastern Phoebe infanticide by non-breeding males may enhance their (Sayornis phoebe) nest in central Kentucky on 22 June reproductive success if the resident female or a new 2008 and documented a case of infanticide. An adult female subsequently pairs with the male and initiates a male phoebe, likely the resident male, was captured at new nest. Received 11 January 2010. Accepted 24 the nest site on 21 June 2008. The resident female fed March 2010. nestlings (3, ,8 days of age) 69 times during a 4.1-hr taping session (0815–1221 hrs EDT) the next day, but the resident male was not observed at the nest. Infanticide has been reported in many species of Beginning at 0923 hrs, an intruding phoebe (likely a male) occasionally visited the nest, sometimes pecking birds, primarily in cooperative breeders, colonial at, but not feeding, the nestlings; this phoebe initiated a breeders, and polygamous species (Freed 1986). vigorous attack at 1151 hrs, pecking and pulling the Infanticide has been reported among socially head of one of the nestlings for 25 min before pulling it monogamous species of birds, but primarily species out of the nest. The intruding phoebe returned after a where breeding opportunities may be limited by short absence, just before the end of the videotape, and biased sex ratios or availability of needed resources began attacking another nestling. The nest was empty such as nest sites (Freed 1986; Robertson and when checked the next day. Suitable territories and nest sites may be limiting factors for Eastern Phoebes, and Stutchbury 1988; Møller 1988, 2004). Infanticide may be adaptive either by providing access to a 1 Department of Biological Sciences, Eastern Kentucky needed resource, such as a nest site (Robertson and University, Richmond, KY 40475, USA. Stutchbury 1988), or by shortening the time until a 2 Corresponding author; e-mail: [email protected] new breeding attempt (Freed 1986). SHORT COMMUNICATIONS 621

Most reports of infanticide among socially behaving differently, was first observed at 0923 monogamous species have involved secondary hrs. Over the next 42 min, this phoebe hovered cavity-nesting species where availability of nest near the nest twice, briefly landed on the edge of sites may limit breeding opportunities (Freed the nest three times, and pecked the head of a 1986, Robertson and Stutchbury 1988, Kermott nestling during two of those nest visits. et al. 1991). We report a case of infanticide by an During the third hour of taping (1015–1115 Eastern Phoebe (Sayornis phoebe), a non-cavity- hrs), the resident female fed nestlings 16 times; nesting species with specific nest-site require- the other phoebe entered the shelter and perched ments that may limit breeding opportunities of on the camcorder four times, but did not visit the some individuals. nest. The resident female continued provisioning nestlings during the fourth hour of taping (1115– OBSERVATIONS 1215 hrs). The ‘intruding’ phoebe entered the We studied Eastern Phoebes at the Blue Grass shelter and perched on the camcorder 21 times Army Depot (BGAD) from mid-March to mid- from 1115 to 1145 hrs, uttering ‘bipeaked July 2008. The BGAD is in Madison County, vocalizations’ (Smith 1969) on multiple occasions Kentucky and encompasses 5,907 ha of pastures and ‘initial peaked vocalizations’ (Smith 1969) with trees and woodlands interspersed throughout. twice. The female visited the nest three times Concrete shelters (about 2.5 3 5 3 2.5 m; n 5 while the other phoebe was on the camcorder; the 54), each with two open doors (1 3 2m)at presence of the intruding phoebe had no apparent opposite corners occur throughout the depot to effect on the female’s behavior. provide depot personnel with protection in case of The intruding phoebe flew to the nest at 1151 emergencies. The shelters are rarely visited by hrs and began vigorously pecking and pulling Army personnel, but phoebes readily enter the one of the nestlings, focusing its attack on the shelters to nest. nestling’s head. This phoebe pecked or pulled at We located a phoebe nest on 21 June 2008 with the nestling about 1,250 times (,50 times/min) three nestlings ,8 days of age in a shelter that, for over the next 25 min. The resident female came security reasons, we visited infrequently. An adult to the nest ,5 sec after the attack was initiated, phoebe entering the shelter was captured in a mist hovered briefly at the edge, then landed with net on the same day and banded with a USGS beak agape and moved to within ,2 cm of the aluminum band and a unique combination of three attacker for ,3 sec. The female then flew from colored-plastic bands. The phoebe was identified the nest, returning 5 sec later and again briefly as a male based on the presence of a cloacal hovered near the nest. As the attack continued, protuberance. Standard measurements were taken the female left and re-entered the shelter and and the male, in apparently good condition, was perched on the camcorder three times (but released. uttered no calls), and flew to the nest and The nest was videotaped from 0815 to 1221 hrs provisioned nestlings five times, uttering no EDT on 22 June 2008 with a camcorder placed vocalizations and not interacting with the 2 m from the nest. The camcorder was protected attacking phoebe. The intruding phoebe pulled from the elements in the shelter so we did not the apparently dead nestling out of the nest at the retrieve the videotape until the next day (23 Jun conclusion of the 25-min attack, and returned to 2008). We subsequently reviewed the tape and the nest ,4.5 min later and began attacking a noted all visits to the nest by adult phoebes as well second nestling. The videotape ended 40 sec as any other recorded behaviors or vocalizations. after this second attack began. An unbanded Eastern Phoebe, apparently the The nest was empty when visited the next day resident female, provisioned nestlings at a rate of with no sign of adult or nestling phoebes in the 16.8 visits/hr during the 4.1-hr videotape; the shelter. We re-visited the shelter 12 days later; the phoebe banded the previous day (assumed to be nest was still empty and we observed no adult the resident male) was not observed at the nest. phoebes in or near the shelter. The female phoebe visited the nest and provi- sioned nestlings 35 times from 0815 to 1015 hrs, DISCUSSION and always exhibited the same behavior, landing Male Eastern Phoebes typically provision at the edge of the nest and quickly feeding a nestlings and defend nest sites and territories nestling. Another phoebe, also unbanded, but from conspecifics (Weeks 1994). Thus, the 622 THE WILSON JOURNAL OF ORNITHOLOGY N Vol. 122, No. 3, September 2010 absence of the male at our focal nest plus the rarely initiated after late June (GR, pers. obs.). presence of the intruding phoebe suggests the A male phoebe acquiring a territory with 8-day- resident male was not present. The male we old nestlings on 22 or 23 June, as in our study, banded at the nest site, likely the resident male, would likely have no opportunity to breed appeared to be in good condition when released. during the current breeding season if those The reason for the male’s absence is unknown, but nestlings developed normally and fledged (gen- could have been due either to abandonment of the erally when 16–18 days of age; Weeks 1994). territory (e.g., as a result of being captured in a Infanticide could potentially provide a male mist net) or predation. phoebe with a breeding opportunity. However, Our observations indicate adult Eastern Phoe- the nest in our study was empty when checked bes at times engage in infanticide. Beheler et al. 12 days later and we observed no phoebes in or (2003:996) also noted instances of infanticide near the shelter, indicating the infanticidal male (‘probably by nonparental adults’) by Eastern phoebe in our study did not subsequently breed Phoebes, and Weeks (1994) reported that infan- in that shelter. ticide at times occurred after a territorial male phoebe disappeared. Phoebes are sexually mono- ACKNOWLEDGMENTS morphic and both males and females utter We thank the U.S. Army for allowing us to conduct ‘bipeaked’ and ‘initial peaked’ vocalizations research at their facility, the EKU Research Committee for (Smith 1969). Thus, we cannot be certain the financial support, and C. E. Braun, H. P. Weeks Jr., and an intruding phoebe in our study was a male. anonymous reviewer for helpful comments. A short video However, the absence of the resident male clip of the infanticidal phoebe attacking and removing the suggests the infanticidal phoebe was a male. nestling is posted at http://www.youtube.com/watch?- Infanticide by male phoebes may enhance repro- v54mVQMpyqlrs. ductive success if the resident female or a new female subsequently pairs with the infanticidal LITERATURE CITED male and initiates another nest. This behavior has BEHELER, A. S., O. E. RHODES JR., AND H. P. WEEKS JR. 2003. been reported in other species of songbirds, Breeding site and mate fidelity in Eastern Phoebes including House Wrens (Troglodytes aedon; (Sayornis phoebe) in Indiana. Auk 120:990–999. Freed 1986, Kermott et al. 1991), Tree Swallows FREED, L. A. 1986. Territory takeover and sexually selected (Tachycineta bicolor; Robertson and Stutchbury infanticide in tropical House Wrens. Behavioral 1988), and Barn Swallows (Hirundo rustica; Ecology and Sociobiology 19:197–206. Møller 2004). GRABER, R. R., J. W. GRABER, AND E. L. KIRK. 1974. Illinois birds: Tyrannidae. Illinois Natural History Suitable territories and nest sites may be Survey Biological Notes Number 86. limiting factors for Eastern Phoebes, and com- KERMOTT, L. H., L. S. JOHNSON, AND M. S. MERKLE. 1991. petition for these resources may be intense Experimental evidence for the function of mate (Beheler et al. 2003). Phoebes occupy a variety replacement and infanticide by males in a north- of woodland and edge habitats (Graber et al. temperate population of House Wrens. Condor 1974), but the availability of suitable nest sites 91:630–636. may be limited in many areas (Weeks 1994). MØLLER, A. P. 1988. Infanticidal and anti-infanticidal strategies in the swallow Hirundo rustica. Behavioral Thus, some adult phoebes may be non-breeding Ecology and Sociobiology 22:365–371. floaters. Supporting this assumption is the rapid MØLLER, A. P. 2004. Rapid temporal change in frequency replacement of dead mates and rapid settlement of infanticide in a passerine bird associated with of territories when new nest sites become change in population density and body condition. available (Beheler et al. 2003). The disappear- Behavioral Ecology 15:462–468. ance of a territorial male represents an oppor- ROBERTSON,R.J.AND B. J. STUTCHBURY. 1988. tunity for non-breeding males to acquire the Experimental evidence for sexually selected infanti- cide in Tree Swallows. Animal Behaviour 36:749–753. resources needed for reproduction. Phoebes are SMITH, W. J. 1969. Displays of Sayornis phoebe (Aves, typically double-brooded (Weeks 1994) and, in Tyrannidae). Behaviour 33:283–322. our study area, second broods are generally WEEKS,JR., H. P. 1994. Eastern Phoebe (Sayornis phoebe). initiated in late May or early June; new nests are The birds of North America. Number 94.