Rewind to 6 February 2020 and my girlfriend and I had just visited Raso on Cape Verde. We had just seen the endemic Raso Lark and were heading back to São Nicolau on the charter boat. As we followed the east coast of Raso, checking the Brown Booby and Red-billed Tropicbird colony there, I caught sight of a seabird flying away from us. All I could see at first is a thin white rump in the silhouette of the bird. I casually said to my girlfriend that it "looks like a Great Shearwater", to which she appeared disinterested and headed below deck. Sometime later she reappeared on deck to see a scene of chaos, me getting very sweary and yelling at the captain to follow that bird and the boat at full speed in pursuit. The bird had subsequently banked and the 'thin white rump' had become a thick, white – gleaming, blindingly white – rump. If you are in the Western Palearctic and you see a Pterodroma with a white rump, it is time to get very excited.
Peter 'lucked in' onto this Black-capped Petrel when returning from Raso on 6 February 2020 (Peter Stronach).
The next 17 minutes were a blur – a good blur! The bird, a Black-capped Petrel, was targeting Red-billed Tropicbirds returning to the colony and harassing them till they dropped their catch. Eventually it flew away out of sight. This sighting was incredible but there were a few details that didn't sit right with me.
The current thinking is that Black-capped Petrel – or 'Little Devil' as it is colloquially named – is a rare vagrant to Cape Verde and the wider Western Palearctic from West Atlantic haunts and Caribbean breeding grounds. At times, this bird was flying right over the land and along the cliffs during broad daylight. Its targeting of tropicbirds was deliberate; after it had parasitised one it flew back out to intercept another knowing full well another would be incoming to the colony. Would a vagrant seabird engage in this behaviour? To me, it felt that it knew that coast and used that knowledge to maximise the food it stole. Maybe it was just a vagrant, perhaps its hunting technique was a spur-of-the-moment decision. Either way, it was enough to get me thinking.
I like projects. I like studying subjects, getting deep down into the details and working out solutions. Recent birding projects with others included proving early autumn is just as good as late autumn for transatlantic passerine vagrants on Corvo, Azores, and a quest to see whether it would be possible to intercept 'Omid', the Siberian Crane, on its spring migration north from Iran (more on that here). So back to Black-capped Petrels and Cape Verde ... is there a chance they are breeding here? Here is a review of the records to date.
- 6 February 2016 – one found by children in the middle of Santa Antão (photo).
- 11 March 2017 – one from a seawatch off El Barril, São Nicolau (account).
- 13 February 2018 – one mistnetted on Santa Antão (photo).
- 28 April 2019 – one at sea between Fogo and Ilhéu de Cima (photo).
- 6 February 2020 – one at sea between Raso and São Nicolau (photo).
- 29 January 2021 – one at sea between Fogo and Ilhéu de Cima (photo).
The interior of Santa Antão. Might the chorus of 'Little Devils' echo around these mountaintops? (Peter Stronach).
To turn the problem on its head, I decided to assume they were breeding and then work out where they were most likely to breed. All known Black-capped Petrel nesting sites are in mountainous areas between 1,500 and 2,000 m above sea level in the thick understorey of steep montane forests of Caribbean islands. It is here where the name 'Diablotín' or 'Little Devil' originates, owing to its eerie call and the sound produced by air moving over its wings during nocturnal flights. A modelling exercise of Caribbean breeding areas identified higher-elevation sites with increased forest cover and those closer to the coast as being ideal. Although this model isn't directly translatable, as the ecology and climate of Cape Verde are very different to the Caribbean, I looked for areas that were forested and above 1,400 m in altitude.
The islands of Cape Verde aren't very large so the near-the-coast factor doesn't really apply. Although São Nicolau does have high areas which are forested in part, the area is small. The island that really stood out as being suitable was Santo Antão, which had large areas above 1,400 m and still with extensive native forest. This island also has the largest population of breeding Fea's Petrels and – most notably – hosts two intriguing inland records of Black-capped Petrel, one mistnetted during a session targeting Fea's Petrels and the other found by children. The decision was made …
The picturesque Ponta do Sol, Santa Antão (Peter Stronach).
We arrived on Santo Antão on 17 February 2023, a trip I had planned to coincide with the new moon and peak petrel activity. After leaving baggage at our accommodation we drove to Ponta do Sol in the island's north-west to get some food and to try an evening seawatch. As I started seawatching at around 4.30 pm from the point by the lighthouse, a very obvious passage of Fea's Petrels was in progress heading east along the coast.
I moved higher along the coast road, counting up the Fea's Petrels got to a total of 134, all of which were either rafting on the surface of the sea or flying east. Remarkably, they apparently have never been seen rafting in the breeding season before! As I scanned through the flocks, a small group took flight and I was amazed to see a Black-capped Petrel among them. The birds would raft for several minutes, then take flight move a bit further east and land again in a raft. I couldn't quite believe it: our first day on the island and I had seen my second Black-capped Petrel in the Western Palearctic!
On 19th I tried again with the same tactic, seawatching off Ponta do Sol and checking the Fea's Petrels as they moved east along the coast. Again another Black-capped Petrel; this time I followed it a long way in the telescope until it was a distant dot. Rotating my scope back left, I started scanning again through the Fea's in front of me when I was amazed to see another Black-capped Petrel among them. There was no way the individual I had just seen as a dot in the distance could have returned so quickly – it was a second bird. Amazingly, when watching the footage back later a third bird is apparent in the melee – bird #2 disappears from shot at c 11 seconds, with bird #3 appearing from stage left at 18 seconds. A similar event occurred the following evening with two birds seen among the gathering Fea's. Just incredible!
Two of three Black-capped Petrels off Ponta do Sol, Santa Antão, on 19 February (Peter Stronach).
So, what do these sightings mean? Well, they don't definitively prove Black-capped Petrel is breeding here, but – and it's a big but – if this level of activity was seen directly offshore of an island in the Caribbean it would be a fair assumption that you had breeding Black-capped Petrels on it. The birds were not parasitising the Fea's Petrels and, there were no negative interactions between them. Both species were behaving in the same way: rafting up and gathering offshore, with the Fea's at least definitely going inland to breeding and courtship areas.
I reported the sightings to the wonderful seabird team from the University of Barcelona Seabird Ecology Lab and Projecto Vito. They very kindly offered to take me out on a ringing expedition to a Fea's Petrel colony and I spent two wonderful nights with Alexsandro and Admilton seeing their incredibly professional work up close. With their ongoing study of Fea's Petrels at nest sites on the island, it is they who provide the best hope of finally proving whether Black-capped Petrel breeds in the Western Palearctic.
Black-capped Petrel off Ponta do Sol, Santa Antão, on 20 February (Peter Stronach).
