 The eggs hatch after about three weeks and the young are attended by both parents. Males are present around the nest for most of the day, and females most of the night. The parents exchange nest duties in the morning and in the evening. Most of the feeding of the chicks occurs during the period where they swap nesting duties. Little feeding is done in the period of the day that is between the two duty swaps and no feeding is done between midnight and 6 a.m. Chick mortality is highest in the first twenty days post hatching, with anywhere from 37 to 83 % of hatchlings surviving to three weeks of age in the Everglades. During periods of food limitations and starvation events, the American white ibis tends to exhibit sex-dependent pre-fledgling mortality. For many bird species that have sexually dimorphic nestlings, mortality rates are higher for larger-sized male nestlings as a result of the parents' inability to meet its greater nutritional needs. However, in the case of the American white ibis, the male nestlings actually have a lower mortality rate as compared to the females despite being on average 15 % greater in mass as compared to its female counterparts. Although current research has yet to discover the underlying factors to why the males tend to have better survival rates under such conditions, it is suspected that the parents tend to feed the larger male nestlings first because they are either perceived by the parents to have a higher chance of survival, or, being generally larger, the male nestlings simply out-compete the small females for food.
