It’s an hour after darkness, the sky muted in dark greys on this overcast evening. There’s not a breath of wind, and yet the roaring sound of the Atlantic swell crashing on the base of the cliffs 15 metres below us would have you think otherwise.
Above the sound of the crashing surf, a chorus of mysterious calls begins to fill the air. Some are repetitive, stuttering calls, squeaky in tone like someone rubbing their finger up and down a pane of glass. These are the Band-rumped Storm-petrelsOceanodroma castro. Also appearing every now and then is a wailing cry very different in nature to these chirruping calls; slower in pace and sounding not unlike the construed ‘cock-a-doodle-do’ of a chicken. Or, as some would describe the Little Shearwater’s call: a cockerel on red bull.
Have a listen to a few of these calls in the above recording, though the quality isn’t amazing. You get a feel for the atmosphere of this seabird colony at night (and that’s in the winter!)
This chorus is a delight to listen to, but we must focus on the task at hand and try not to get distracted by the surrounding cacophony and ghostly shapes darting above the cliff edge like swallows. We are here to carry out an evenings’ mist netting session, with the purpose of catching some of these elusive birds returning to the islet by darkness. With the use of a fine mesh net strung up between two poles, we’re able to catch birds periodically as they fly unsuspecting into the soft pockets of the net.
It’s just light enough to pick out the wriggling shapes once birds have flown into the net, and we take it in turns to trundle over and delicately extract these amazing creatures for further study. What we hope to achieve through this procedure is a greater understanding of the population of ‘Madeiran’ Storm-petrels which utilise Praia Islet as a breeding site, and also a greater understanding of these birds’ biology: what their survival rate is like, how faithful they are to specific breeding colonies (or even nest sites) on islands like Praia, what they feed on (yes, they do throw up on you from time to time as you’re extracting them…), what patterns of moult they undertake, and even looking at identification features which build allow us to distinguish them from their newly-allocated cousin the Monteiro’s Storm-petrel (previously thought to be the same species). There are many questions which remain unanswered when it comes to these seafaring creatures.
The previous days have had us occupied helping Veronica Neve deploying GPS loggers onto some birds on the islet, but this evening we are fitting only standard metal rings to these birds: each ring with a unique code that will allow us to keep track of its movements and whereabouts should it appear again in our nets and nest boxes, or those anywhere else (fingers crossed). And we both hope they will indeed return, especially with over 160 nest boxes scattered across the islet, created specifically for these petrels to nest within. Many are occupied already, but there are still vacant ‘homes’ available for new breeders.
It’s now 8pm. The moon is just rising on the eastern horizon, visible as a lightening in the sky to the south of Terceira – another island the Azores whose light pollution casts a faint orange glow onto the clouds above it. As the darkness becomes less obsolete, the chorus of petrel chattering and shearwater wailing dies away, until it becomes bizarrely quiet. And yet simultaneously we’re suddenly met with a flurry of birds flying into the net over the coming hour, keeping us very busy with the constant extraction, ringing and processing of the Madeiran Stormies fluttering about. Why this change in activity occurred isn’t entirely clear. I would usually anticipate nocturnal seabird activity to die away as the moon rises, as the risk of predation from the likes of gulls increases.
Either way, there is a pulse of activity until well after 10pm, when we bring the ringing session to an end and close the net. Out last two birds have fairly typical weights for the night – 49.9 grams and 48.7 grams – barely half the weight of a blackbird. Yet these ocean-goers spend most of their time over the open seas, navigating featureless landscapes to find food, migrate and return to their breeding colonies. A spectacular feat for such a delicate little bird. It’s a real privilege to be able to study these petrels intimately as part of Hannah’s research, and it’s exciting to think of the mysteries and unanswered questions lingering over their lives even now.
We release the last bird of the night; it sits in the palm of Hannah’s hand and is silhouetted against the night sky after we switch our head-torches off. After a ruffle of feathers, it peers about and flutters off into the night, its bright white rump patch disappearing off in the direction of the cliff. Until next time…
Take a look at the sound approache’s introduction to the fascinating Band-rumped Storm-petrels and their vocalisations if you’re after a bit more information about these awesome seabirds, and there will be plenty more to come here too, so watch this space.