 The American white ibis pairs up in spring and breeds in huge colonies , often with other waterbird species . Nesting begins as soon as suitable foraging and nesting habitat is available . The female selects the site , usually in the branches of a tree or shrub , which is often over water , and builds the nest , and males assist by bringing nest material . Anywhere from one to five eggs are typically laid , with two or three being the most common . The eggs are matt pale blue @-@ green in color with brown splotches and measure 5 @.@ 8 cm × 3 @.@ 9 cm ( 2 @.@ 3 in × 1 @.@ 5 in ) and weigh on average 50 @.@ 8 g ( 1 @.@ 79 oz ) . Clutch sizes are usually lower in coastal colonies as compared to inland colonies , although there are no statistically significant differences in the fledging rate of both colonies . Throughout the mating and incubation period , the male undergoes a period of starvation to stay close to the nest and aggressively defend his nest and mate from both predators and other ibises in preference to foraging for food . In the 2006 breeding season , a non @-@ breeding adult female was observed to be tending to multiple nests that belonged to other American white ibises — the first time the behavior has been documented for this species . 
