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Left-sided Directional Bias of Cloacal Contacts During Tree Swallow Copulations
Peer Reviewed Publications
  • Aaron D Petersen, Hope College
  • Michael P Lombardo, Grand Valley State University
  • Harry W Power, Rutgers University - New Brunswick/Piscataway
Publication Date
Most female birds have only a left ovary and associated oviduct with entry to the oviduct on the left side of the urodeum of the cloaca. We hypothesized that male cloacal contacts during copulation would occur from the left side of females because this would put sperm closer to the entrance of the oviduct. We observed that cloacal contacts from the left outnumbered those from the right by a margin of 3:1 during tree swallow, Tachycineta bicolor, copulations at nestboxes in western Michigan in 1999. The directional bias of cloacal contacts may have an adaptive function.
  • tree swallows,
  • <em>Tachycineta bicolor</em>,
  • aves,
  • birds,
  • copulation,
  • sexual behavior in animals,
  • cloaca
Citation Information
Aaron D Petersen, Michael P Lombardo and Harry W Power. "Left-sided Directional Bias of Cloacal Contacts During Tree Swallow Copulations" (2001)
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