“January 2022 has brought with it a number of winter storms and gales affecting the Bermuda area, with one gale on the 13th-14th Jan. bringing winds gusting up to 54 to 68 knots (62 to 80 mph). Calm spells to get out in a small craft to visit and survey the Cahow nesting islands have been few and far between, but J-P Rouja, Carla Marquardt and myself were able to get out on Sunday 16th January to carry out a check of nest burrows on Long Rock and Nonsuch Island, and shoot a video of the latest check of the CahowCam 1 (# R831) nest to find out what was happening.
In particular, Carla was able to candle Cahow eggs that were being incubated by the adults, while I carried out weight and body condition checks and band checks of the adult Cahows. Candling can determine whether an egg is fertile or not, and check on the development of the embryos inside fertile eggs. Although a number of eggs had failed on Long Rock, indicating that breeding success rates will be low, possibly impacted by disruption to and disturbance of the burrows after this very low-lying islet was completely submerged by 20-foot waves during near-miss hurricanes during both 2020 and 2021. On Nonsuch Island, however, a higher percentage of the eggs already laid that were checked were fertile and their embryos developing normally, probably helped by the fact that the nest sites on this island are at much higher elevation and were not impacted at all by hurricane flooding and erosion.
Regarding the CahowCam 1 nest, the adult birds at this nest returned and laid their single egg on the night of 8th January. JP and I were able to visit Nonsuch on the 9th, and it was noted that the egg was not only quite large at 60 grams weight but was unusually long & elongated in shape. This can sometimes indicate that the egg will not be fertile (although we have had chicks hatch successfully from elongated eggs before!). Nevertheless, it was a relief when Carla was able to confirm that the egg was in fact fertile, with a normally developing 7-8 day old embryo. The Cahows in the other, CahowCam 2 nest are always one of the last pairs to return and had not returned yet as of this check. The CahowCams can be seen here: http://www.nonsuchisland.com/live-cahow-cam
At this point, about 90 % of all pairs have returned to lay their eggs. A number of male birds had arrived first and were waiting for the arrival of their mates, so that they could start the first and longest incubation shift. During this time the female returns to sea for 7 to 14 days while the male cares for the egg, living off accumulated fat reserves. The female needs this recovery period to feed and recover after laying an egg which can be a fifth to a quarter of her body mass - the equivalent of a human having a 30-lb baby! This is the reason Cahows can only produce 1 egg a year.
24 hours after making this check of the islands, Bermuda is again being lashed by heavy rain and winds gusting to gale-force. It will likely be a couple of days before we can make the next visit to the islands, during which we will continue to check nests on the remaining nesting islands to get a better idea of how many chicks of Bermuda's critically endangered National Bird we can expect for this nesting season."
Jeremy Madeiros | Principle Scientist - Terrestrial Conservation | Dept. of Environment and Natural Resources