Depleted fish stocks threaten seabird survival

Brian Unwin, The Telegraph 11 Jul 08;

Mass nesting failure year after year is threatening the future of world famous spectacular seabird colonies - and climate change could be the cause.

The warning signs may not be apparent to the tourists enjoying views of kittiwakes, guillemots and puffins on the cliffs of Sumburgh Head at the southern tip of Scotland's Shetland Isles or at remote Fair Isle, 25 miles out to sea.

"Wildlife is a major reason why people take holidays on Shetland and during a short visit there's so much to see at Sumburgh that many possibly don't realise there's a serious problem as they enjoy the sights", said Martin Heubeck an Aberdeen University seabird specialist based on the islands.

"But anyone spending all afternoon observing the sea birds closely through a telescope soon realises something is wrong - the birds aren't actually doing anything other than, in effect, hanging around and being photographed.

"They aren't repeatedly flying in from the sea with fish, nor are they busy feeding or giving other care to their chicks. Most likely they don't have any youngsters - and probably any that do won't be feeding them because they're struggling to find fish.

"Clearly this cannot continue indefinitely. Repeated breeding failure means an increasing proportion of older birds in populations - and with no young birds coming through to replace them when they die, the future survival of their colonies is threatened."

This crisis has been taking shape since the mid-1980s with the disappearance of the immense sand-eel shoals that used to sustain the birds through the breeding season.

Commercial overfishing was initially blamed but stocks didn't recover after it was banned. This led to new suspicion that climate change could be responsible; perhaps sea temperature changes were causing the fish to move to new waters, or affecting their own survival, leaving the birds without their staple diet.

Mr Heubeck is "depressed" about the impact on the colonies on which his whole working life has been focused. While the birds keep returning each spring to follow their instinct to nest, he detects signs of decline in their commitment level.

"Nesting success depends to a great extent on being in a good condition", he explained. "If they return to the colonies and there is insufficient fish around, they are liable to concentrate on finding food rather than breeding or attending their nest sites.

"The stress on them in the pre-breeding period is such that they are not socialising and forming proper colonies as in the past. They need to establish their nest sites and get to know their neighbours on the cliff ledges.

"But all that is breaking down now. Increasingly we see birds returning to the colonies in spring then deciding not to breed - putting their own survival first. The situation is leading to irreversible declines - the results of the next Northern Isles seabird census will be dramatically different to those of the last one during 1998-2001."

It's hard to work out the full effect of the sand-eel famine on seabirds throughout Shetland, which is made up of more than 100 islands spread over almost 600 square miles. However, a grim impression has emerged from detailed studies on Fair Isle, Britain's most isolated inhabitated spot 25 miles south of Sumburgh.

Deryk Shaw, warden of the bird observatory on the 3.5 miles by 1.5 miles isle that has been home to up to 250,000 seabirds of 18 species, has just produced a report about the unfolding cataclysm. It includes two graphs tracing the decline of two common species since the 1980s.

In the case of the shag, nesting numbers have risen just six times in 25 years; mostly progress has been downwards and now it's at a new low point. With kittiwakes, it's even worse - an almost continuous slide from around 23,000 nests to under 3,000.

Summaries of performances this summer produce no signs of hope for the long-term strugglers:

• Shag: Nest numbers on monitoring plots have fallen by 58 per cent since last year to an all-time low and the vast majority of these were abandoned at an early stage. In a "normal year" up to 400 chicks are fitted with leg rings to help trace future movements - this summer only five have been ringed.

• Arctic skua: After several poor breeding seasons the number of territories has plummeted to just 37 (the lowest since the colony's establishment in the 1950s - apart from equally disastrous year 2004 when there were only 33). No young have been produced.

• Kittiwake: The number of nests is only half of that counted as recently as 2005 (2,688 compared to 5,433) with many birds just standing on bare ledges.

• Guillemot: The number of eggs on monitored plots was 57 per cent down on last year. Of 92 eggs there, just two chicks were produced and both were predated. "It was a similar story on trips into colonies around the isle with hardly any chicks to be found and those that were present being small and weak, unlikely to fledge."

• Razorbill: Many eggs and chicks were produced but they have been dying steadily. None is expected to fledge from the entire island.

• Puffin: Many eggs laid but results are expected to be poor. Food is scarce - adults returning mostly with rockling (a tiny silvery fish) and gadoids (mainly whiting fry) with a very few small sand-eels.

Significantly his reports don't mention Arctic terns. That's because they arrived in the spring only to depart due to failure to find fish - a particularly tragic end to their journey from their winter territory in the southern oceans to nest in this far north location.

The picture was similar last year - after their return only a few eggs hatched and all the chicks died. In 2006, 300 chicks fledged, a notable exception after five consecutive years of total failure, with the number of nesting birds declining annually.

Mr Shaw told how visiting colonies has become a gloomy operation. "A normal descent into a big guillemot colony armed with hundreds of rings and measuring gear is a highlight of our season and the noise has to be experienced to be believed.

"Recent years have been met with an eerie silence - the only sounds have been the plaintive cries of a few weak and dying chicks. Normally the first visit into one of these colonies alone would see us ring up to 500 chicks but this year, not one was ringed from the entire island. The only rings fitted were to the few adults we managed to catch."

The significance of the sand-eel in this disaster is underlined by the fact two of Fair Isle's breeding seabirds - gannet and the internationally rare great skua - that don't depend on them are doing well.

Apparently occupied great skua territories have increased from 224 in 2007 to 294 this summer, a rise of 31 per cent. The world population is only about 17,000 pairs and 40 per cent are on the Shetland Isles so this rise represents a big plus.

This species is bucking the trend through being a predator and a scavenger - with rabbits and other seabirds included in its diet. Rising gannet numbers are linked to their widespread foraging and ability to catch larger fish like mackerel and herring.

Mr Shaw stresses research into what is happening to the food chain is "desperately needed" because there were crucial questions in need of answers.

"Why can't birds find enough food? Are sand-eels just not there any more and why? Is it due to 'climate change' and/or is it over fishing or something else entirely? Are the sand-eels simply not breeding or has their breeding season shifted such that their presence no longer coincides with the seabird breeding season?"

There is a further question that emphasises his and Mr Heubeck's growing concern that the declining colonies may be heading towards total collapse. It is: "Are we too late to save our seabirds?"

Seabird colonies on the Orkney Isles, 50 miles south of Shetland, are similarly in dire straits.

The picture there is also of nests abandoned and empty cliffs, says the Royal Society for the Protection of Birds while urging the Scottish government to put the environment at the heart of planned new marine legislation.

RSPB Scotland ecologist Doug Gilbert said: "Regrettably the poor breeding performance of our internationally important seabird colonies is now an annual theme. When you look at the evidence over the last 15 years it is quite startling and cause for serious concern.

"At our Copinsay reserve on Orkney the kittiwake population has plummeted drastically since the mid 1980s, when there were at least 10,000 birds on the cliffs, but today there are just under 2,000, a pattern repeated in many areas of Scotland and the UK.

"This decline is a major conservation problem, as Scotland supports 45 per cent of the nesting seabirds in the EU, and the colonies attract many visitors to marvel at the sight of the massed colonies."

As on Shetland, the lack of sand-eels and other small fish such as sprats, is the problem.

"Adult birds are having to spend more time away from their eggs and chicks to find food and many are just giving up their breeding attempts this year. “These changes are almost certainly being driven by changes in the sea environment about which we still know little. Seabirds are indicators of the health of the marine environment - and, like the canary in the coalmine, the decline in their fortunes should be a wake-up call to which we must all pay attention."