Historically, based on decades of meticulous recordkeeping the Cahows have been known to return for nestbuilding, courtship, and mating for the month of November, go back to sea for December to feed and recharge whilst the female develops her single egg, and once again return in early January for egg laying and the start of the 2 month incubation process. If all goes well, this is followed by the chick hatching in early March and fledging in late May / early June.
This timing has evolved over millennia to be during the winter, (as opposed to during the summer as in most bird species), and is theorized to have developed so as to avoid the hurricane season which runs from June through October. (*It also conveniently falls during the school year, so is perfect for our educational outreach purposes notes Nonsuch Expeditions founder J-P Rouja).
More recently though, likely triggered by climate change, many of the Cahows have been documented returning earlier and earlier into October, with this year’s October 14th return of the CahowCam1 male being the earliest on record.
Whilst not as much of a concern for the Nonsuch Island colonies that were built 50+ ft above sea-level for this very reason, some of the burrows on the original nesting islands get completely over-swept during hurricanes and are under major threat not only from physical damage to the concrete burrows, with concrete lids routinely being swept off etc. but even more concerningly when early returning birds overlap with late season hurricanes as we look to be facing later this week...
A few years ago, late season Hurricane Gonzalo impacted Bermuda with large ocean swells which over-swept Green Island and drowned several Cahows that had returned early and were already in their nests.
After a rather frustrating late summer/early fall, Bermuda has felt the effects of 3 near-miss hurricanes (Erin, Humberto and Imelda) but fortunately none of the Cahows were back yet.
However now, as the currently decreasing yet still threatening Hurricane Melissa lines up to pass Bermuda on Thursday night as a Cat 2, even if it keeps its current track passing to the West, the accompanying swells are predicted as of this writing to be as high as 35ft feet. These depending upon their direction could completely over-sweep the Green Island and Long Rock colonies which would be a disaster, as many of the pairs on those islands will be back and hunkered down in their nests...
We can only hope that Melissa's path to the west of Bermuda will reduce the size of its accompanying swells and surge, which generally are larger if a storm passes to the east or southeast of the island. All we can do is hope for the best and assess the damage on the smaller original nesting islands once the hurricane, (hopefully the last of this season!), is past the island and conditions calm enough to get back out in the boat...
Stay tuned for updates and watch CahowCam3 surface-cam during the storm which we will keep focused on Green Island to monitor the conditions during daylight hours.