 Within a colony , a male bird will occupy an ' activity space ' , which will overlap with the activity spaces of other males . Males with overlapping activity spaces form associations called ' coteries ' , usually consisting of 10 to 25 birds . Coteries are the most stable unit within the colony . The birds also form temporary flocks when engaged in the same activity . These flocks , called ' coalitions ' , usually comprise five to eight birds , although coalitions of up to 40 birds can occur when mobbing a potential predator . Membership of the coalition changes frequently as individuals leave the group as it passes beyond the boundary of their activity space , or the activity ends or changes , as when the breeding season begins . Females use activity spaces that overlap with those of male birds , but not other females , so that females will join coalitions with males in their area , but only rarely will there be more than one female in the coalition . The exclusivity of female activity spaces leads to young females being driven out of the colony in which they were born , and also makes it difficult for them to gain a place in a new colony . A study of banded nestlings that survived in one colony until the next breeding season , found that they were all male birds , suggesting that all female nestlings had died or left the colony . Emigration of males does not seem to occur until the population density of the colony reaches a critical level . 
 Within a colony , a male bird will occupy an ' activity space ' , which will overlap with the activity spaces of other males . Males with overlapping activity spaces form associations called ' coteries ' , usually consisting of 10 to 25 birds . Coteries <a href='drop_aux' title='1'><mark>are</mark></a>the most stable unit within the colony . The birds also form temporary flocks when engaged in the same activity . These flocks , called ' coalitions ' , usually comprise five to eight birds , although coalitions of up to 40 birds can occur when mobbing a potential predator . Membership of the coalition changes frequently as individuals leave the group as it <a href='uninflect' title='2'><mark>passes</mark></a> beyond the boundary of their activity space , or the activity <a href='uninflect' title='3'><mark>ends</mark></a> or changes , as when the breeding season <a href='uninflect' title='4'><mark>begins</mark></a> . Females use activity spaces <a href='null_relcl' title='5'><mark>that</mark></a>overlap with those of male birds , but not other females , so that females will join coalitions with males in their area , but only rarely will <a href='dey_it' title='6'><mark>there</mark></a> be more than one female in the coalition . The exclusivity of female activity <a href='uninflect' title='7'><mark>spaces</mark></a> leads to young females being driven out of the colony in which they <a href='uninflect' title='8'><mark>were</mark></a> born , and also <a href='uninflect' title='9'><mark>makes</mark></a> it difficult for them to gain a place in a new colony . A study of banded nestlings <a href='null_relcl' title='10'><mark>that</mark></a>survived in one colony until the next breeding season , found that they <a href='uninflect' title='11'><mark>were</mark></a> all male birds , suggesting that all female nestlings <a href='been_done' title='12'><mark>had</mark></a> died or left the colony . Emigration of males <a href='uninflect' title='13'><mark>does</mark></a> not seem to occur until the population density of the colony <a href='uninflect' title='14'><mark>reaches</mark></a> a critical level . 
Within a colony , a male bird will occupy an ' activity space ' , which gon overlap with the activity spaces of other males . Males with overlapping activity spaces form associations called ' coteries ' , usually consisting of 10 to 25 birds . Coteries the most stable unit within the colony . da birds also form temporary flocks when engaged in the same activity . These flocks , called ' coalitions ' , usually comprise five to eight birds , although coalitions of up to 40 birds can occur when mobbing a potential predator . Membership of the coalition changes frequently as individuals leave tdagroup as it pass beyond thdaoundary of their activity space , or thedativity end or changes , as when the breeding season begin . Females use activity spaces overlap with those of male birds , but not other females , so dat females will join coalitions with males in their area , but only rarely will it be more than one female in the dalition . The exclusivity of female activity space leads to young females being driven outt of the colony in which they was born , and also make it difficult fa them to gain a place in a new colony . A study of banded nestlings survived in one colony until the ndabreeding season , found tdatthey was alll male birds , suggesting that all female nestlings done died or left the colony . Emigration of males do not seem to occur until the population density of the colony reach a critical level .