Bermuda Petrel/Cahow 2023 Breeding Season Update: January 26th 2023
Several survey trips to Nonsuch Island and the other Cahow nesting islands were carried out in the brief calmer gaps in the otherwise windy, rainy conditions that have been prevalent since November, 2022. In addition, the arrival of our two overseas collaborative researchers in January means that the next stage of study of the Cahow's At-sea Range has begun with the retrieval of GLS tags fitted 2 years ago to the legs of adult Cahows, and the deployment of additional tags of 3 different types, to check overall distances traveled, foraging areas and depth of feeding dives/amount of time spent on the surface of the ocean compared with flying time, etc. In addition, Carla Marquardt has begun the inspection & candling of Cahow eggs of differing ages to determine whether eggs are fertile or infertile, and to monitor embryo age, development and health.
On Nonsuch Island, essentially all breeding pairs have returned and have laid their eggs and begun incubation. Three additional new breeding pairs have laid their first eggs, bringing the total number of confirmed breeding pairs on Nonsuch to 33. In addition, 2 other established pairs returned but did not produce any eggs, and 3 new prospecting pairs established nest sites, bonded and will hopefully produce their first eggs next year.
We had a rare opportunity to check all four adult Cahows from the two CahowCam nests, as both pairs remained together in their nest burrows incubating their eggs. We were able to confirm that all four adults were in good condition and at good body weights. Carla was able to inspect both eggs, and there is both good and bad news; firstly, it was confirmed that the large egg in the CahowCam 1(R831) nest is definitely infertile. This possibly was the result of the female bird staying at the nest with the male for less than two weeks during the vital courtship, nest-building and mating stage of the breeding season in late October and November, (as confirmed by the CahowCam and flagged by several of our volunteers / followers), leaving extremely early on the 6th November. Normally Cahows fly to sea during the last days of November, and the male bird did in fact stay at and tend the nest faithfully for the rest of the month. The female may simply not have stayed together with the male long enough to ensure fertilization of the egg.
Note from JP: Whilst this egg failure is disappointing, it is within the historical success rate of this particular pair (+/- 50%) and in fact for the Colony as a whole, which averages around 55%, please see prior post explaining this.
Now, the good news is that Carla was able to confirm that the egg in the CahowCam 2 (R832) nest is indeed fertile, continuing the remarkably good breeding success history of this particular pair, which started nesting in 2010 and have produced a total of 11 successfully fledged chicks with only 2 failures in the 13 years up to 2022. This is one of the most successful breeding pairs on Nonsuch, and hopefully they will be able to add to this great record for this year!
We will continue to provide updates as the season progresses through the rest of the 50-53 day incubation period, with the first chicks due to hatch in early March.
Jeremy
Jeremy Madeiros Principle Conservation Officer (Terrestrial Conservation) Dept. of Environment and Natural Resources BERMUDA