Seasonal breeder

Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the optimization of survival of young due to factors such as ambient temperature, food and water availability, and changes in the predation behaviors of other species. Related sexual interest and behaviors are expressed and accepted only during this period. Female seasonal breeders will have one or more estrus cycles only when she is "in season" or fertile and receptive to mating. At other times of the year, they will be anestrus, or have a dearth of their sexual cycle. Unlike reproductive cyclicity, seasonality is described in both males and females. Male seasonal breeders may exhibit changes in testosterone levels, testes weight, and fertility depending on the time of year.

Seasonal breeders are distinct from opportunistic breeders, that mate whenever the conditions of their environment become favorable, and continuous breeders, like humans, that mate year-round.

The breeding season is the most suitable season, usually with favorable conditions and abundant food and water for breeding. Abiotic factors such as the timing of seasonal rains and winds can also play an important role in breeding onset and success.

Many species breed in colonies or large communities, known as communal breeding. It is common to see large congregations of these species in particularly favorable locations during their breeding seasons. These breeding colonies and their locations are generally protected by wildlife conservation laws to keep the species from going extinct. Some species have evolved for communal breeding in large breeding colonies and cannot breed in smaller numbers or pairs alone. These species can be threatened by imminent extinction if they are hunted on their breeding grounds or if their breeding colonies are destroyed. The passenger pigeon is a famous example of probably the most numerous land bird on the American continent which had evolved for communal breeding. Due to large scale hunting in its communal breeding grounds during the breeding season and its inability to breed in smaller numbers, the passenger pigeon went extinct.

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