Ascension : Conservation Weekly
Submitted by The Islander (Conservation Office) 20.12.2007 (Article Archived on 03.01.2008)

You may remember from previous Conservation Weekly articles, that our RSPB colleague, Dr. Mark Bolton, was coming to try and capture a few Madeiran storm petrels. Is it possible that the storm petrels on Ascension may be different from those in the North Atlantic.

Notes from a night at the Letterbox

You may remember from previous Conservation Weekly articles, that our RSPB colleague, Dr. Mark Bolton, was coming to try and capture a few Madeiran storm petrels. Is it possible that the storm petrels on Ascension may be different from those in the North Atlantic. In order to solve the mystery, we needed to collect some feather samples for genetic testing and take body measurements of the birds. Both of these required the capture of the birds themselves. For this reason, I had the pleasure of accompanying Dr. Bolton and volunteer Dr. Bob Langton to the Letterbox last Monday afternoon.

We started walking around 15:30 pm with our well-packed rucksacks, Mark definitely having a heavy load as his kit included a mist net, tagging materials, camera, loud speaker, sleeping bag, water, among other food and provisions. We hiked down the goat path, around the chalky cliffs, downhill in the scree until reaching the gut just before the Letterbox plateau. We followed the gut until it ended at an old lava flow.

After climbing down the flow we made a brief scramble up a cliff to scout for a good netting location, then followed the flow to its end at a sea cliff opposite Boatswain Bird Island. It was here that we set up camp and erected the temporary field station for the evening, just before it grew dark. The plan was to set up the net and play the storm petrel calls until a bird flew into the net. First to go up was the mist net. This fine net was erected on the cliff edge and stretched between two poles. The next step was playing the bird calls. Mark used a mp3 player attached to a megaphone. For the next 12 hours, we would play calls of Madeiran storm petrels at volumes loud enough to attract the birds from nearby Boatswain Bird Island. After a final check of the net, we grabbed a quick bite to eat and waited eagerly for the first storm petrel to arrive. Luckily, our wait was short as the circling frigate birds and boobies were soon joined by an occasional storm petrel. It was really exciting to watch these small birds flying low and calling. Soon the occasional bird grew to groups of 4 or 5, with more birds calling around us. Given that Madeiran storm petrels are typically nocturnal, we weren’t sure exactly how many were present on Boatswain Bird or nearby areas. It was very promising to hear and see so many of them.

Brood patch

Eventually, darkness fell and the mist net became less visible to the birds. Around 21:00, we caught the first storm petrel of the evening. Mark sprung into action (literally!), quickly and deftly freeing the bird from the net and safely securing it in a cloth bag. Bob was tasked with watching the net for more birds whilst Mark and I recorded data on the captured petrel. By 21:15 Mark had rung the first Madeiran storm petrel on the island since the1950’s! This truly was a historical event and gave us enthusiasm to continue capturing the birds throughout the night.

I was amazed to observe the petrels up close. They were much smaller than I expected, with soft feathers and tiny webbed feet. I got my first glimpse of a “brood patch”: a small square of bare skin, designed to keep the petrel parent’s warm bellies in close contact with their incubating eggs. Data collection involved taking several measurements of the bird: various wing and bill lengths, feather stages, and body weight. A few feathers were taken for samples for genetic analysis as well.

Around 3 am the loudspeaker batteries faded, giving us a momentary and admittedly most welcome respite from the recorded bird calls. Unfortunately, the quiet of the loudspeaker also gave way to quiet from the local petrels, so the loudspeaker was back on in a matter of minutes. Aside from a couple of rain showers, we had good working conditions and plenty of time to enjoy the unique setting. By 6 am, the sky grew light and the storm petrels stopped flying. For our evening’s efforts we had captured and rung 12 petrels in the first successful netting attempt in several decades. We began the long hike uphill to return to the Landrover, happy with the knowledge that storm petrels are still present on Ascension. The morphological data that we collected suggest that the Madeiran storm petrels on Ascension may be different from North Atlantic storm petrels. We’ll have to see if the genetic analysis will tell us more about our “stormies”.

HAPPY HOLIDAYS TO EVERYONE AND A SPECIAL THANK-YOU TO OUR VOLUNTEERS!!!