 The nest is a shallow scrape in the sand on open , flat or occasionally sloping ground . It is often unlined , but sometimes includes stones or cuttlefish bones . One , sometimes two , eggs are laid and incubated by both parents for 25 to 30 days prior to hatching . The eggs are cream with blackish streaks . Egg laying is synchronised within a breeding colony and more tightly so within sub @-@ colonies . Parents do not recognize their own eggs or newly hatched chicks , but are able to distinguish their chicks by the time they are two days @-@ old , shortly before they begin to wander from the nest . The precocial chicks , which are very pale with black speckling , are brooded and fed by both parents , but may gather in crèches when older . The young terns fledge after 38 to 40 days , but remain dependent on the parents after leaving the colony until they are about four months old . 
