Patterns of sperm storage in relation to sperm competition in passerine birds

Article Abstract:

The number and length of sperm storage tubules (SST) in 20 species of passerine birds encompassing seven subfamilies were estimated using a method for observing SSTs in oviduct tissue preparations. A ninefold variation across species was found for the average number of SSTs per female which was positively correlated with body mass and egg size. Interspecific variation in SST number was attributed to allometry. Selection for greater sperm length in the presence of limited access to storage sites was suggested. Evidence was obtained for a history of coevolution between sperm and sperm storage sites in females which is independent of body size.

Passeriformes, Perching birds, Spermatozoa, Sperm

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Male incubation in Barn Swallows: the influence of nest temperature and sexual selection

Article Abstract:

A study was conducted to ascertain the role of male Barn Swallows (Hirundo rustica) in the incubation process. Four colonies of barn Swallows were observed in southeastern Canada during the 1989 breeding season. The study showed that 9% to total incubation time during the day was contributed by the males. The maximum contribution was made during the early morning hours, when female swallows needed to replenish energy reserves lost during night incubation, and during the last stages of incubation. Factors such as extra-pair copulations and male attractiveness did not hinder the contribution of male Barn Swallows to incubation.

Canada, Ornithological research, Eggs, Bird eggs, Bird nests, Eggs (Biology), Incubation, Swallows, Barn swallow

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Lack of sperm storage by female migrants and the significance of copulations en route

Article Abstract:

Sperm from insemination during migration probably do not retain viability in migratory birds. Copulations occurring en route may be an epiphenomenon resulting from the need to be ready to breed on arrival at the breeding grounds. Females appear to have either a developed specialized sperm storing tubule (SST) or an undeveloped SST during migration. A study conducted on 11 female migrant birds indicates that the proportion of migrating females with a developed SST is probably low as they remain undetected with a relatively small sample.

Bird migration, Sexual behavior in animals, Animal sexual behavior

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