( Typically ( ( ( the bird ) ( in ( the lead ) ) ) ( ( is ( ( the male ) ( of ( a ( mated pair ) ) ) ) ) . ) ) )
(ROOT (S (ADVP (RB Typically)) (NP (NP (DT the) (NN bird)) (PP (IN in) (NP (DT the) (NN lead)))) (VP (VBZ is) (NP (NP (DT the) (NN male)) (PP (IN of) (NP (DT a) (JJ mated) (NN pair))))) (. .)))
Typically the bird in the lead is the male of a mated pair.
(ROOT (S (NP (NNP Birds)) (VP (VB pair) (PRT (RP up)) (PP (IN with) (NP (NP (DT the) (JJ same) (NN bird)) (PP (IN in) (NP (NN mating) (NN season)))))) (. .)))
Birds pair up with the same bird in mating season.