▁observations , ▁un season al ▁nest ing ▁( or ▁nest ing ▁outside ▁of ▁the ▁mon so on ) ▁of ▁sar us ▁c ran es ▁were ▁thought ▁to ▁be ▁due ▁to ▁either ▁the ▁presence ▁of ▁two ▁populations , ▁some ▁pairs ▁raising ▁a ▁second ▁bro od , ▁and ▁un success ful ▁bre eding ▁by ▁some ▁pairs ▁in ▁the ▁normal ▁mon so on ▁season , ▁prompt ing ▁them ▁to ▁nest ▁again ▁when ▁conditions ▁such ▁as ▁flo oded ▁mar sh es ▁remain . ▁A ▁compreh ensive ▁assess ment ▁of ▁un season al ▁nest ing ▁based ▁on ▁coll ation ▁of ▁over ▁ 5 , 0 0 0 ▁bre eding ▁records , ▁however , ▁showed ▁that ▁un season al ▁nest ing ▁by ▁sar us ▁c ran es ▁in ▁south ▁Asia ▁was ▁very ▁rare ▁and ▁was ▁only ▁carried ▁out ▁by ▁pairs ▁that ▁did ▁not ▁succeed ▁in ▁raising ▁ch icks ▁in ▁the ▁normal ▁nest ing ▁season . ▁Un season al ▁n ests ▁were ▁initi ated ▁in ▁years ▁with ▁unusual ▁ra inf all ▁patterns , ▁when ▁ra inf all ▁extended ▁beyond ▁the ▁normal ▁June – Oct ober ▁period , ▁and ▁when ▁ra inf all ▁volume ▁was ▁higher ▁than ▁normal ; ▁or ▁when ▁artificial ▁wet ▁habit ats ▁were ▁created ▁by ▁man - made ▁structures ▁such ▁as ▁res er voir s ▁and ▁ir rig ation ▁can als ▁to ▁enh ance ▁c rop ▁production . ▁N est ▁init iation ▁in ▁northern ▁Queensland ▁is ▁also ▁closely ▁tied ▁to ▁ra inf all ▁patterns , ▁with ▁most ▁n ests ▁being ▁initi ated ▁immediately ▁after ▁the ▁first ▁major ▁ra