The cloaca of a Brown Booby. Note that it's the small dot just before the bird's feet.
Dunnocks performing cloacal pecking.
Cloaca (kloh-AY-kah; from Latin, a sewer[1] ): the combined opening of the digestive, urinary, and reproductive systems of many vertebrates, including monotremes, birds, fish and reptiles; also in some invertebrates.[2]
In birds[]
In birds, urine and feces from the digestive tube, and sperm and eggs from the reproductive organs, all pass out of the body through a common passage, the cloaca.[1]
The cloaca is incompletely separated into three compartments: the copropodeum, into which the large intestines empties; the urodeum, into which the ureters and genital ducts empty; and the proctodeum, with which the coprodeum and urodeum communicate and which opens to the outside of the body through the vent, or anus, which is the external opening of the digestive tract.[3][1]
Mating[]
Most species of birds do not have a phallus, and so they mate via a cloacal kiss, where the two birds press their cloacae against each other long enough for the male to transfer sperm to the female. Some species of bird, such as the duck, have a phallus that they use to help with copulation, rather than by performing a cloacal kiss. Only 3% or so of birds have a phallus, so most mate via the cloacal kiss.
Oviposition[]
During oviposition, the cloaca of a female will evert outside of her vent. This helps both to help stop the flow of uric acid to the urodeum, as well to provide a way for the gentle release of the egg, rather than letting it merely fall out.
References[]
- ^ a b c Terres, John K. (1980). The Audubon Society Encyclopedia of North American Birds. Alfred A. Knopf, Inc. ISBN 0394466519.
- ^ France, Peter, Guerrero, Angeles Gavira; et al. (2006). Ocean. Dorling Kindersley Inc. ISBN 9780756636920.
- ^ Berger, A.J. (1961). Bird study. New York: John Wiley & Sons, Inc.
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