Do Northern Saw-whet Owls ( Aegolius acadicus ) maintain kin associations during fall migration?

1. Do Northern Saw-whet Owls (Aegolius acadicus) maintain kin associations during fall migration? Caitlyn Stromko* and Karl Kleiner, York College of Pennsylvania, Department of Biological Sciences, York, PA 17403 Methods Breast feathers were sampled from hatch year Northern Saw-whet Owls caught in the same net check or on the same night during fall migrations of 2004-2006. Banding stations were located in Montana (Teton County) and Pennsylvania (Cumberland, Dauphin and Schuylkill counties). Total genomic DNA was extracted and a 711 nucleotide base pair fragment of the tRNA-Glu/control region of the mitochondrial DNA was amplified through PCR (Figure 1). • Discussion • Owls were more likely to be different than the same. • Based on our sampling it does not appear that sibling Northern Saw-whet Owls maintain kinship after fledging, suggesting migratory behavior is instinctual rather than learned. • Only one potential sibling pair based on sharing an identical genetic sequence was revealed, but the two owls were caught in different states during the same migration year. • These data hint at nomadic behavior in Northern Saw-whet Owls. Abstract Migratory birds that maintain post-fledging kin associations often do so to structure the formation of their flocks. Terns, cranes, geese, swans, and other waterfowl are known to migrate together in family groups of parents and young. Little is known about the kin associations of migratory owls. In this study, we used a genetic analysis to examine forty fall migrating Northern Saw-whet Owls (Aegolius acadicus) from Pennsylvania and Montana to answer the question: do Northern Saw-whet Owls maintain kin associations during annual migration? A 711 nucleotide base pair fragment of the tRNA-Glu/control region of the mitochondrial DNA was used to detect closely related individuals. No owls captured in the same net check or on the same night had the same genetic sequence. Only one potential sibling pair based on sharing an identical genetic sequence was revealed, but the two owls were caught in different states during the same migration year. Based on our sampling it does not appear that sibling Northern Saw-whet Owls maintain kinship after fledging, suggesting migratory behavior is instinctual rather than learned. Sorenson et al., 1999 Literature Cited Andersson, M. and Wallander, J. 2004. Kin selection and reciprocity in flight formation? Behavioral Ecology 15(1): 158–162. Barlow, M. 1998. Movements of caspian terns (Sterna caspia) from a colony near Invercargill, New Zealand, and some notes on their behavior. Notornis 45: 193– 220. Black, J. M. and Owen, M. 1989. Parent-offspring relationships in wintering barnacle geese. Animal Behavior 37: 187–198. Lee, J., Lee, Y. and Hatchwell, B.J. 2010. Natal dispersal and philopatry in a group-living but noncooperative passerine bird, the vinous-throated parrotbill. Animal Behaviour 79: 1017–1023. O’Toole, L.T., Kennedy, P.L., Knight, R.L. and McEwen, L.C. 1999. Postfledging behavior of golden eagles. Wilson Bulletin 111(4) : 472–477. Payne, R.B., Payne, L.L. and Doehlert, S.M. 1987. Song, mate choice and the question of kin recognition in a migratory songbird. Animal Behavior 35: 35–47. Sorenson, M.D., Ast, J.C., Dimcheff, D.E., Yuri, T. and Mindell, D.P. 1999. Primers for a PCR-based approach to mitochondrial genome sequencing in birds and other vertebrates. Molecular Phylogenetics and Evolution 12(2): 105–114. Tóth, Z., Bókony, V., Lendvai, A.Z., Szabó, K., Pénzes, Z. and Liker, A. 2009. Whom do the sparrows follow? The effect of kinship of social preference in house sparrow flocks. BehaviouralProcesses 82: 173–177. Figure 1. Diagram of a portion of mtDNA from Gallus gallus. Bracket indicates region copied by PCR. Mitochondrial DNA was used for its characteristic maternal inheritance. Sibling owls will yield identical nucleotide base sequences, as may closely related kin (Figure 2). PCR products were purified and sequenced, and the sequences were trimmed to 703 base pairs and aligned to produce a phylogenetic tree to detect closely related individuals (Figure 3). Further alignments were conducted to evaluate genetic relatedness of owls based on the results of the phylogenetic tree. • Introduction • Kin associations in bird species are used to promote fitness and to impact social and reproductive behavior. Some birds maintain kinship well after fledging, such as house sparrows, vinous-throated parrotbills, and golden eagles (Tóthet al. 2009, Lee et al. 2010, O’Toole et al. 1999). • Other birds retain no lasting bonds to family members post-fledging, such as indigo buntings(Payne et al. 1987). • Migratory birds that maintain post-fledging kin associations often do so to structure the formation of their flocks (Lee et al. 2010). Terns, cranes, geese, swans, and other waterfowl are known to migrate together in family groups of parents and young (Black and Owen 1989, Barlow 1998, Andersson and Wallander 2004). • This kin-biased behavior is driven by its benefits: protection against predation and harassment, the development of socially facilitated behaviors, such as foraging and exploration, and the knowledge of migratory routes for survival. • Despite its importance, few studies have investigated the maintenance of kinship among migratory birds. Little is known about the kin associations of owls. Post-fledging behavior has not been investigated. • Our question was: Do Northern Saw-whet Owls maintain kin associations during annual migration? Figure 2. Sequence alignment of two owls caught during the same migration season yielding identical sequences. Location abbreviations: KG, King’s Gap, PA; M, Choteau, MT. • Results • The forty owls were sampled from 12 net checks across the 4 banding stations. • The maximum number of hatch year owls in a single net check was 3 and the maximum number on a night was 4. • No owls captured in the same net check or on the same night had the same genetic sequence. • The minimum number of different nucleotide bases for owls sampled from the same net check or on the same night was two, and this was limited to only 1 pair of owls. • The range of base differences for owls caught in the same net check was 3 to 16. For owls caught on the same night, the range of base differences was 3 to 11. • Only two owls, 1 from Pennsylvania (KG2) and 1 from Montana (M4), sampled from the same season (2004) yielded an identical genetic sequence. Acknowledgments I would like to thank Scott Weidensaul and the Ned Smith Center for Nature and Art for their support and feather samples from Pennsylvania. The Montana feathers are courtesy of Graham Frye. Figure 3. Phylogenetic tree of owls banded at three sites in Pennsylvania and one site in Montana. Location abbreviations: KG, King’s Gap, PA; HV, Hidden Valley, PA; SV, Small Valley; M, Choteau, MT.