Shetland can be a magical place in the summer. Catherine Munro writes about the storm petrels at Mousa Broch.
We stepped onto the small boat as the sun dipped below the horizon, filling the sky with the colours of fire. The mirror sea, feeling no wind, reflected the fading colours of the day. As the island drew nearer, anticipation rose, we were about to experience a very special seabird encounter.
The island of Mousa is home to 12,000 breeding pairs of storm petrels, around 40% of the UK population. A distant relation to the albatross, these tiny birds spend their winter months around the coast of Africa, and thousands return to Mousa each year to breed.
We followed a rugged path towards the nest site. The reds in the sky have begun to change, replaced by subtler shades of grey and blue. The green of the island was surprisingly vibrant, remaining bright, even as the light of the day began to fade. Our guide stopped us by a tumbled down wall. ‘listen’ he said. As from behind the stones came the strangest sounds. A rusty rumble, insistent, continuous, punctuated with a regular, almost indignant sounding, squeak. We were told that a previous visitor had said it sounds like a fairy being sick. Surprisingly this seemed to accurately describe the sounds we heard.
As we stood, we were told about the Storm Petrel’s amazing survival strategies. The birds, on their search for food, can travel hundreds of miles, regularly leaving their nests for days at a time. While incubating an egg, birds take it in turns to stay on the nest while the other searches for food. The bird on the nest can lose 20% of its body mass. Should the partner be away to long, and the remaining adult face starvation, they may have to go fishing, leaving their egg, alone and exposed. Amazingly, the chick inside the egg can survive several days while both parents are away. Once hatched, the chick retains this ability to survive. When short of food, the chick can enter a state of torpor to conserve energy. Often appearing dead to worried human observers, a few drops of fish oil provided by returning parents, is enough to revive these chicks.
As he spoke, the guide’s affection towards these birds was clear. He confessed that for a long time he hadn’t been a very ‘birdy’ person but then he started to regularly work on the island. Through sharing his life with the petrels, his respect and admiration for them had grown.
The group walked in near silence, listening out for sounds in the walls and stony beaches beside the path. The petrels stayed quiet while the drumming of snipe and piercing call of a distant oystercatcher filled the still night air. As we followed the path downhill, the broch suddenly towered above us, silhouetted against the light grey sky. Standing at 13 meters high, this Iron Age tower, is the best preserved in the world, and two thousand years after it was last inhabited by humans, it is now home to storm petrels.
Placing a hand on the Broch, the smooth lichen covered rocks felt cold. How many hands have touched these walls? The presence of history was all around, the past close enough to touch. From within the walls, came the sound of petrels, making the building and the very air around us seem to vibrate. The Broch itself becomes a living being.
The first fleeting shapes began to arrive on silent wings. I stood close to the Broch looking up, the silhouettes of birds fill the luminescent sky, flitting around the ancient walls. As the night grew darker, more and more birds joined the dance. There were sounds of scrabbling as birds land clumsily against the walls, before disappearing through gaps between the stones. Birds were everywhere, we were surrounded. Some swooped surprisingly close, the wind from their wings the only motion in the still night air.
Too soon, it is time to go. In a line we wound our way back along the path towards the boat. The rocky beaches that seemed so empty on our arrival were alive with the calls of petrels waiting for their mates to return with food. I stand for a moment listening to the song of a tiny bird, a worldwide traveller and born survivor, each one incubating an egg, from which a new life will soon emerge.