On November 19, 2025 Jeremy and I were taking a group of visiting birders on a tour of Nonsuch and visited the southwest point. Upon reaching the clearing, we came across a horrifying site, first one, then two, then three, and finally four carcasses of what clearly were Cahows, now just their wings, attached only by a portion of their rib cage, completely stripped bare of all flesh, their bodies, heads, legs (and identifying leg bands) completely gone.
The immediate consensus from Jeremy and the experts among the group was that this was the work of a bird of prey such as an Owl or raptor such as a Falcon, but which one was it, and was this just the tip of the iceberg? It is known that a Peregrine Falcon was spotted during early to mid-November by Jeremy and private boaters over the Airport and Castle Harbour Islands area and was even seen roosting on the cliff edge on Nonsuch very close to where the Cahow carcasses were found, making this the primary suspect.
However, back in 1987 Jeremy’s predecessor Dr. David Wingate was faced with a similar tragedy, when a Snowy Owl blown in by a storm proceeded to take up residence nearby and developed a taste for Cahows, killing at least 5 (representing 5% of the species at the time), mainly on one of the original nesting islets, Green Island (they were not re-introduced to Nonsuch Island by Jeremy until 2004).
It was eventually shot by Dr. Wingate as a last resort, after multiple efforts to capture or tranquilize the Owl were unsuccessful. To this day this action is still controversial in the birding world and just recently someone somewhat prophetically asked me if Jeremy had yet faced his own “Snowy Owl moment”. At the time the entire Cahow population on the planet consisted of only a few dozen pairs and would have returned to its previously assumed extinction, should the Owl have been permitted to continue with its Cahow diet.
Cahows, are nocturnal, and will only approach land after sunset, conducting all of their aerial courtship, and activities outside of their underground burrows after dark. This behavior likely evolved as a way to avoid daytime-hunting eagles, hawks and falcons. However as was documented by at least two similar kills 15 years ago, also on Nonsuch, Peregrine Falcons have also been known to hunt them under the light of a full moon and are well-documented as being able to hunt the related and similar-sized Manx Shearwater, during full moon periods on islands off the coast of Wales.
There had been a Super Full Moon earlier in the month and the state of the carcasses was such that these kills could have happened around that time, and a Peregrine Falcon had been seen roosting on Nonsuch around the time as well... Historically when they are blown in to Bermuda they will stay for a week or two until they build up their energy and fat reserves, and then resume their migration heading south to the Caribbean and South America, which would in these circumstances be the best case scenario, as this might limit the killings to the few we had found already, but what if it was another Owl?
The visiting birding group, led by Bob Flood have been coming to Bermuda since 2012, in November, when they charter a vessel to take them several miles offshore in the late afternoon to photograph Cahows in flight. The cahows are returning for courtship and congregate there, staying out of reach of land based raptors until after sunset when they make a beeline to Nonsuch and the surrounding colonies under cover of darkness.
The following night this same group along with Jeremy and Peter Drew, his assistant, were positioned just off of Nonsuch to document the Cahows near-shore dusk approach, when a Short-eared Owl was witnessed flying from Nonsuch over to Green Island where it appeared to be hunting, instantly making it a suspect as well. Short-eared Owls are on the smaller side, and likely couldn’t catch a Cahow in flight, though could conceivably attack a younger prospecting one, exposed on the ground at night.
During the prior Owl hunting episode, Cahow carcasses were found on the crest of Green Island so we determined that checking there, especially for more recent kills during moonless nights, would indicate that our perpetrator might be an Owl, and that we had an ongoing bigger problem...
This increased the urgency for us landing on Green, which has remained logistically inaccessible to us since before the passage of Hurricane Melissa, which itself had had the potential to catastrophically impact the nesting burrows there. As outlined in prior posts, due to its late in the year passage when the burrows were already occupied by Cahow pairs, we were still not sure as to the height of the storm-surge when it made its closest approach around midnight, as if it had fully submerged the island as had happened in prior hurricanes, it would likely have resulted in Cahow drownings...
On Nov 21st, Jeremy and I were finally able to land there, after being dropped off by Peter and in the first instance were able to confirm that most fortunately there had been little to no hurricane damage, with only one burrow lid having been knocked off. We quickly made our way to the top of the island and after examining all of the clearings, mirrored by Peter also checking the nearby clearings on Nonsuch, are very happy to say that no further, carcasses, feathers or signs of Cahow kills were found.
Taking all of the above into account Jeremy believes that it is likely that the perpetrator was in fact the Peregrine Falcon, which seems to have since left the island after feasting on the four Cahows that we found on Nonsuch, so hopefully that is the end of this matter, at least for this season. The DENR, the Nonsuch Expeditions and project partner BioQuest will now attempt to extract DNA from the carcasses, which once compared to birds from their ongoing Cahow Genomic Population Study, should be able to determine if the victims were young prospecting Cahows or older ones, perhaps part of established pairs which would be far more disruptive to the ongoing recovery program.
Either way, Jeremy says that we should be on the lookout, as whilst the recovery program successfully increases the size of the Colonies, it will likely also attract more threats such as this.
For a bit more good news from Green Island: Jeremy was able to conduct a detailed nest check and the one burrow the lid from which had been knocked off during the hurricane, was left with an open roof until he replaced it, so its resident pair was not able to occupy it.
However when checking a nearby nest he did find the somewhat muddy female from that open nest and was able to return her to her now fixed burrow, and in doing so not only set her nesting season back on track, but avoided a potential fight when her temporary burrows regular occupants returned...
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