 On occasion early in the breeding season , mass displays erupt , where twenty or thirty birds perform the various wing @-@ spreading displays , short flights , and constant calling . Displaying birds are attacked by others , and groups of silent but agitated birds watch the interactions . Mass displays are more common in the early morning , can last for up to 40 minutes , and seem to be a combination of sexual and agonistic behaviour . 
 On occasion early in the breeding season , mass displays erupt , where twenty or thirty birds perform the various wing @-@ spreading displays , short flights , and constant calling . Displaying birds are attacked by others , and groups of silent but agitated birds watch the interactions . Mass displays <a href='drop_aux' title='1'><mark>are</mark></a>more common in the early morning , can last for up to 40 minutes , and seem to be a combination of sexual and agonistic behaviour . 
On occasion early in da breeding season , mass displays erupt , where twenty or thirty birds perform tdavarious wing @-@ spreading displays , short flights , and constant calling . Displaying birds r attacked by others , and groups of silent but agitated birds watch the interactions . Mass displays more common in thdaarly morning , can last fir up to 40 min , and seem to be a combination of sexual and agonistic behaviour .