Puffins in peril

The puffin seems poised to join the list of British seabirds whose numbers are declining. So Mike Harris spent a year studying a colony to pinpoint the cause of the problem.

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The much-loved puffin seems poised to join the list of British seabirds whose numbers are declining. Many experts blame climate change for reducing food during the breeding season, but Mike Harris believes that we have to experience a whole year in a puffin colony to really pinpoint the problem.

 
It’s a grey overcast day in early April on the Isle of May. The Edinburgh skyline and outline of the Forth bridges are just visible to the west and, far out to sea, a small dot appears on the horizon. It rapidly increases in size, suddenly turning into a puffin that lands with a splash on the water 50 metres away.
 
This bird has probably not seen land for five months and, for part of that time, it will have been flightless while moulting its main wing feathers. Now it can fly again, it is returning to its colony.
 
Little friar of the sea
 
Except for a few black smudges on its face – the remnants of its winter plumage – this bird looks immaculate, having regrown the bright feathers, eye ornaments and bill plates that give it such a distinctive appearance.
 
Swiss naturalist Konrad Gessner’s original scientific description from 1570 is very apt: “If you imagine that this bird was white, and that you then put on a black cloak with a cowl, you could give this bird the name of ‘little friar of the sea’ Fratercula marina.”
 
The specific name marina was replaced with arctica by the Swedish taxonomist Linnaeus in 1758 to reflect its northern range. Today, it also suggests a species that may not cope with rising sea temperatures.
 
Return to land
 
The first puffin is soon joined by others and together they bob on the sea – it will be up to a week before they take their first tentative steps on land. Newly returned birds are nervous but, as the days pass, they gain confidence and begin reclaiming the nesting burrows they used the previous year.
 
Puffins are among the earliest seabirds to lay eggs. They are in a hurry because it takes three months to rear a chick and all the birds must leave by early August to spend time feeding intensively before the winter.
 
If a bird has lost its mate since the last breeding season, there is usually just enough time to find a new partner and clean out an unused burrow, but rarely sufficient time to dig a new one.
 
Together forever?
 
Most puffins court and mate at sea before returning to land, so there is great scope for infidelity. But DNA studies on Norwegian puffins suggest that, once birds pair off, they exhibit a high degree of faithfulness.
 
By early May, the colony is very quiet. Each couple now has a single egg and the only birds to be seen are those relieving their incubating partners in the mornings and evenings, or those still trying to find a mate or burrow.
 
Welcome home
 
I visit the island every spring, eager to see how many of the puffins we ringed in previous seasons have survived the winter. Last year, there was an added incentive. With the help of colleagues from the Centre for Ecology and Hydrology, I also counted every occupied burrow on the island – a task we undertake once every five years as it’s such a huge colony and the job has to be carried out quickly before spring vegetation hides the nesthole entrances.
 
The Isle of May’s puffin population had been increasing by 11 per cent per annum for 40 years, and we anticipated at least 100,000 pairs in 2008. To our dismay, we found just 42,000 and I fear there will be a similar decline in 2009.
 
But why is this happening?
 
Usually, 85 per cent of our ringed puffins return. We always miss a few birds and some may take a year off breeding, so the true annual survival rate is likely to have been more than 90 per cent. But for the past two years it has fallen to below 60 per cent.
 
In 2008, we caught and weighed returning puffins and found that they were significantly lighter than the birds we captured 10 years ago – further evidence that something untoward is happening at sea before they arrive at the colony. Puffins are long-lived and can cope with a few poor reproductive seasons, but not with such a large loss of breeding adults.
 
Something fishy
 
As I walked across the island in late May, an odd-looking puffin circling overhead caught my eye. A glance through my binoculars revealed that it was carrying fish – proof that the colony’s first egg had hatched. The bird landed and shot down its burrow to feed its chick before it could be accosted by any thieving gulls.
 
Within days, fish-laden puffins filled the skies, and my colleagues could start collecting discarded booty to examine the catch of the day. As ever, sandeels were predominant, but they were smaller than last year’s, continuing a 30-year trend. Today, the sandeels brought in by puffins measure just 5cm long, compared to 7–8cm in the 1970s.
 
A meagre meal
 
If the sandeels are small, a puffin must increase the number it catches per trip in order to provide enough food for its chick. In 2008, the average catch was 15, up from 5 when the study began in 1972. Since a puffin can carry 70 or more sandeels in one beakful, this is a very small load, and weighing in at just 1–2g, it is of limited value to a growing chick.
 
Puffins also bring in other fish. Some, such as sprats, are highly nutritious, but others, such as snake pipefish, can only be described as junk food.
 
Clearly, something is going on in the seas nearby. In the past 20 years, the temperature of the UK’s coastal waters has risen by up to 2°C, particularly the North Sea. This is driving out coldwater plankton, the key prey of sandeels, and encouraging organisms that favour warm conditions.
 
Snake pipefish are increasing, too, presumably because there is more food for them. But while this explains breeding failures, it doesn’t tell us why adults are disappearing over the winter. To find out more, we have to follow the birds for the rest of the year.
 
Crash landing
 
One early morning in late June, I was intrigued by a rustling in the nettles behind my house on May. Moments later, I discovered a three-quarter-sized adult puffin with a sooty bill – the first fledgling of the year.
 
Chicks usually leave their burrows and head out to sea at night to escape predators. But this one had obviously made a mess of things, perhaps lured by the noise of our generators (we turned them off at night from then on), and was very vulnerable. We rescued it, launched it from a clifftop and watched it fly away with a whirr of wings.
 
There is a myth that young puffins are deserted by their parents, but, if anything, the opposite is true. A chick leaves when it wants to, and its parents return with fish the next morning to find an empty nest.
 
Even after their offspring has fled, they will continue to visit their burrow to ensure that another bird doesn’t take possession of it in anticipation of the breeding season the following year.
 
Summer in the colony
 
July is the busiest month at the puffinry, since the birds spend more time ashore where they are joined by immature birds from previous years.
 
We ring many chicks in their burrows before they fledge and our records show that if a youngster survives the winter, it will come back to the general area where it was born the following July. However, it will only visit land briefly, preferring to spend most of its time at sea with thousands of other birds.

 

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