page_title: Communal roosting
section_title: Birds
hierarchical_section_title: Communal roosting / Examples by species / Birds
caption_attribution_description: English: A Rook (Corvus frugilegus) roost near Nyíregyháza, Hungary. Magyar: Vetési varjak (Corvus frugilegus) Nyíregyháza közelében. Русский: Грачи (Corvus frugilegus) возле города Ньиредьхаза, в Венгрии. Français&#160;: Des Corbeaux freux (Corvus frugilegus), près de Nyíregyháza, Hongrie
context_page_description: Communal roosting is an animal behavior where a group of individuals, typically of the same species, congregate in an area for a few hours based on an external signal and will return to the same site with the reappearance of the signal. Environmental signals are often responsible for this grouping, including nightfall, high tide, or rainfall. The distinction between communal roosting and cooperative breeding is the absence of chicks in communal roosts. While communal roosting is generally observed in birds, the behavior has also been seen in bats, primates, and insects. The size of these roosts can measure in the thousands to millions of individuals, especially among avian species.
  There are many benefits associated with communal roosting including: increased foraging ability, decreased thermoregulatory demands, decreased predation, and increased conspecific interactions. While there are many proposed evolutionary concepts for how communal roosting evolved, no specific hypothesis is currently supported by the scientific community as a whole.
context_section_description: Communal roosting has been observed in numerous avian species. As previously mentioned, rooks (Corvus frugilegus) are known to form large nocturnal roosts, these roosts can contain anywhere from a few hundred to over a thousand individuals. These roosts then disband at daybreak when the birds return to foraging activities. Studies have shown that communal roosting behavior is mediated by light intensity, which is correlated with sunset, where rooks will return to the roost when the ambient light has sufficiently dimmed.
  Acorn woodpeckers (Melanerpes formicivorus) are known to form communal roosts during the winter months. In these roosts two to three individuals will share a cavity during the winter. Within these tree cavities woodpeckers share their body heat with each other and therefore decrease the thermoregulatory demands on the individuals within the roost. Small scale communal roosting during the winter months has also been observed in Green Woodhoopoes (Phoeniculus purpureus). Winter communal roosts in these species typically contain around five individuals.
  Tree swallows (Tachycineta bicolor) located in southeastern Louisiana are known to form nocturnal communal roosts and have been shown to exhibit high roost fidelity, with individuals often returning to the same roost they had occupied on the previous night. Research has shown that swallows form communal roosts due to the combined factors of conspecific attraction, where individual swallows are likely to aggregate around other swallows of the same species, and roost fidelity. Tree swallows will form roosts numbering in hundreds or thousands of individuals.
  Red-billed choughs (Pyrrhocorax pyrrhocorax) roost in what has been classified as either a main roost or a sub roost. Main roosts are constantly in use, whereas the sub roosts are used irregularly by individuals lacking both a mate and territory. These sub roosts are believed to help improve the ability of non-breeding choughs to find a mate and increase their territory ranges.
  Interspecies roosts have been observed between different bird species. In San Blas, Mexico, the great egret (Ardea alba), the little blue heron (Egretta caerulea), the tricolored heron (Egretta tricolor), and the snowy egret (Egretta thula) are known to form large communal roosts. It has been shown that the snowy egret determines the general location of the roost due to the fact that the other three species rely on it for its abilities to find food sources. In these roosts there is often a hierarchical system, where the more dominant species (in this case the snowy egret) will typically occupy the more desirable higher perches. Interspecies roosts have also been observed among other avian species.
caption: Rooks forming a nocturnal roost in Hungary
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