The return of the Cahow (Bermuda petrel) breeding population to lay their single eggs in their underground nest burrows (watch LiveStream here) on the Castle Harbour Islands has begun in earnest, despite the gale-force winds currently sweeping across Bermuda.
I was able to go out to Nonsuch Island on the last day (Dec. 31st) of 2024, confirming the 1st returned female bird (band no. E0215) in the R833 nest. After returning from the open ocean and carrying out courtship, mating and nest-building in late October & November, Cahows return to sea for 5 weeks during late Nov. and December to feed intensively, the female to develop her single large egg, the male to pack on fat reserves to start the first long incubation of the egg, lasting up to 15 days, while the female returns to sea to recover from laying an egg that masses 20% or more of her body weight. This female was at a healthy post-laying weight of 340 grams, while her egg weighed 56 grams.
Yesterday on 3rd January 2025, I travelled out to Nonsuch in rough conditions with student Noah DeSilva (who was collecting soil samples on Nonsuch for a study) to carry out another check ahead of today's forecast gale. Cahows had returned to a total of 5 nests, upon checking the R833 nest, the male bird (band no. E0276, translocated as a chick to Nonsuch in 2008 and weighing in at an impressive 446 grams) had returned and was incubating the egg, while the female had left him to it and returned to sea.
In addition, one male Cahow (band no. E0853) was sitting in the R829 nest waiting for the return of the female (no egg yet), a newly returned female (band no. E0623) was in the R825 nest incubating a newly laid 59-gram egg and waiting for the return of her mate, while female no. E0768 was incubating a 55-gram egg in the R819 nest. In the R818 nest burrow, a newly returned adult Cahow was incubating an egg, so probably the female bird (not disturbed).
I thought that with a gale commencing later that night, that we would see a surge of returning Cahows flying in and returning to lay their eggs, as Cahows seem to love strong winds. Sure enough, the infrared "surface cam" at the "A" Cahow colony, viewable on the nonsuch expeditions website, captured a good number of Cahows zooming in over the colony, especially between 8pm and 9pm. I was even able to see a couple of them land, possibly at the R834 and R835 nests, and hurry inside their burrows.
Gale and Storm-force winds have been blowing all morning, reaching 52 knots (60mph) at the airport and 64 knots (75mph) at the Bermuda National Museum, accompanied by squally showers. Strong winds are due to continue for at least a few days more, so I expect by the time I get back out to the islands, many more of this critically endangered seabird will be back and contentedly incubating their single eggs!
If you are interested, watch the surface cam over the next several nights on visit the CahowCam page and scroll down until the surface cam comes up. In addition, Cahows in the CahowCam 1 webcam nest are due to return any night now, in previous years they have returned anywhere between 7th to 10th January.