Breeding pairs of cahows have returned to Bermuda to nest, with the first eggs expected to hatch late next month.

Jeremy Madeiros, the Department of Environment and Natural Resource’s principal scientist for terrestrial conservation, said that while he hoped the season would be a record-breaker, only about half of breeding pairs would be successful.

"Cahows have a relatively low breeding success rate of 49 per cent to 56 per cent, although 60 per cent has been attained a couple of years through considerable management of almost every breeding pair,“ he said.

“In contrast, the white-tailed tropicbird, or longtail, which also nests on Nonsuch and the other nesting islands, typically have breeding success rates of 68 per cent to 80 per cent.

“This may be partly due to the longer egg incubation period and also to the fact that cahows are much longer-lived than tropicbirds, at 40 to 50 years compared with 18 to 25 years, which leads to a higher build-up of pesticide and chemical residues in their tissues from agricultural and industrial run-off into the world's oceans.”

Last season there was a record 156 confirmed pairs that produced an egg, from which a record 77 chicks successfully fledged.

Breeding pairs have taken up occupancy in both CahowCam burrows and have laid eggs, with cameras catching one of the males “allopreening” – grooming its mate.

“Allopreening is usually carried out between both members of an established pair to calm and reassure each other and to cancel and neutralise any aggression between the individuals, often seen when pairs first see each other after spending weeks or months mostly alone on the open ocean,” Mr Madeiros said.

“The adults will similarly preen the chicks for five to ten minutes before feeding them, as the chick is so aggressive and desperate for food that the parents cannot feed it, and the preening noticeably calms the chick enough to permit the proper transfer of food.”

To watch the LiveStreams and highlight replays of key events, visit www.nonsuchisland.com.