Extra-pair paternity in eastern bluebirds: effects of manipulated density and natural patterns of breeding synchrony
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The causes of variation in rates of extra-pair paternity among avian populations remain unclear, but could include environmental factors such as breeding density and synchrony. By experimentally manipulating nest site availability, we tested the effects of breeding density on the frequency of extra-pair paternity in eastern bluebirds (Sialia sialis). We also examined the role of breeding synchrony on extra-pair paternity using natural timing of nests. Microsatellite analysis revealed 34 of 305 nestlings (11.2%) were the result of extra-pair fertilizations; and 21 of 79 broods (26.6%) had at least one extra-pair nestling. Several measures of breeding density had independent effects on extra-pair paternity. First, experimental plot type affected extra-pair paternity, with 28 of 34 (82.4%) extra-pair young from nests in high density areas, and only six (17.6%) from nests in low density areas. Independently of plot type, the number of breeding neighbors within a 320-m radius was a significant predictor of the likelihood of extra-pair paternity at the nest. Extra-pair paternity was associated with temporal factors such as absolute timing of breeding and natural levels of local breeding synchrony, but only in bivariate comparisons. We found a positive interaction between density of neighbors within a 320-m radius and local breeding synchrony; this term reduced the main effects of synchrony and number of neighbors, but not experimental treatment. Our results demonstrate the importance of utilizing multiple aspects of proximity in breeding density analyses and testing for interactions between ecological factors that can influence the behavioral events leading to extra-pair fertilizations.
KeywordsBreeding ecology Mating system Nest box density Extra-pair copulation Sialia sialis
We thank the University of Kentucky for use of laboratory facilities for paternity analysis, Jackie Bennett, Emily Clemons, and Barb Kieffer for help in the field, and Diana Torres and Ian Stewart for help in the lab; all of these individuals contributed significantly to the success of this project. We also thank Jackie Augustine, Radovan Vaclav, and two anonymous reviewers for providing helpful comments on previous versions of the manuscript.
The authors declare that all experiments comply with current United States laws.
Conflict of interest
The authors declare that they have no conflict of interest.
- Birkhead TR, Biggins JD (1987) Reproductive synchrony and extra-pair copulation in birds. Ethology 74:320–334Google Scholar
- Birkhead TR, Moller AP (1992) Sperm competition in birds: evolutionary causes and consequences. Academic, LondonGoogle Scholar
- Chuang HC, Webster MS, Holmes RT (1999) Extrapair paternity and local synchrony in the black-throated blue warbler. Auk 116:726–736Google Scholar
- Conrad KF, Robertson RJ, Boag PT (1998) Frequency of extrapair young increases in second broods of eastern phoebes. Auk 115:497–502Google Scholar
- Crawley MJ (2002) Statistical computing: an introduction to data analysis using S-Plus. Wiley and Sons, New YorkGoogle Scholar
- Gowaty PA, Plissner JH (1998) Eastern bluebird (Sialia sialis). In: Poole A, Gill F (eds) The Birds of North America, No. 381. The Birds of North America, Inc, Philadelphia, pp 1–31Google Scholar
- Griffith SC, Stewart IRK, Dawson DA, Owens IPF, Burke T (1999) Contrasting levels of extra-pair paternity in mainland and island populations of the house sparrow (Passer domesticus): is there an “island effect”? Biol J Linn Soc 68:303–316Google Scholar
- Grubb TC Jr (1989) Ptilochronology: feather growth bars as indicators of nutritional status. Auk 106:314–320Google Scholar
- Lack D (1968) Ecological adaptations for breeding in birds. Methuen, LondonGoogle Scholar
- Lubjuhn T, Bruen J, Gerken T, Epplen JT (2001) Inconsistent pattern of extra-pair paternity in first and second broods of the great tit Parus major. Ardea 89:69–73Google Scholar
- Major DL, Barber CA (2004) Extra-pair paternity in first and second broods of eastern song sparrows. J Field Ornith 75:152–156Google Scholar
- Meek SB, Robertson RJ, Boag PT (1994) Extrapair paternity and intraspecific brood parasitism in eastern bluebirds revealed by DNA fingerprinting. Auk 111:739–744Google Scholar
- Pitts TD (1985) Identification of second-year and after-second-year eastern bluebirds. J Field Ornithol 56:422–424Google Scholar
- SAS Institute (1989) SAS user’s guide: statistics. SAS Institute, Cary, NCGoogle Scholar
- Tucker JW (1990) Male eastern bluebird rears four broods during one season. Wilson Bull 102:726–728Google Scholar
- Vaclav R, Hoi H (2002) Importance of colony size and breeding synchrony on behaviour, reproductive success and paternity in house sparrows Passer domesticus. Folia Zool 51:35–48Google Scholar
- Westneat DF, Sherman PW, Morton ML (1990) The ecology and evolution of extra-pair copulations in birds. In: Power DM (ed) Current ornithology. Plenum Press, New York, pp 331–369Google Scholar