I've just about finished the shearwater survey and it seems the numbers in our four monitoring plots are stable. The survey doesn't involve a telescope or binoculars or sitting at cliff edges like most of my other work. Instead I crawl around a grassy slope stopping at anything which looks like a burrow and listen to see if anyone is home! Ok, so that's not the exact methods...
Shearwaters nest in burrows on the large grassy slopes on the western side of the island. It's sometimes easy to tell if a burrow is occupied due to broken vegetation, squirts, disturbed soil or feathers, but not always. It's made more complicated because puffins nest in the same area which means these obvious clues could belong to either species. This is why a simple count of 'active' burrows isn't an option and why we rely on other methods.
Shearwaters are active at night and mostly silent during the day but will respond to the call of another bird if prompted. The survey takes advantage of this and involves playing a call at each burrow and then waiting to hear if something responds. The call of a shearwater is a most ridiculous sound probably best described as a loud shrill wheezing noise which is peculiar to hear seeping out of the grass slopes (click here to hear for yourself).
A burrow at the bottom of the plot had clear signs of use but there was always silence in response to the tape. That was until a few days ago when after playing the call for what felt like the one millionth time a bird appeared at the entrance and starting pecking at the tape player. That's never happened before and it caught me totally by surprise!
I took the tape player away as I now clearly knew the burrow was occupied but the wee chap poked his head out a bit further for a few more seconds before he turned around and waddled back to his egg.
Just another day surveying seabirds!