The great seabird mystery
Post categories: In depth
| 16:05 UK time, Monday, 8 June 2009
This year for Springwatch I'm investigating the great seabird mystery: why are some colonies doing fine while others are in crisis?
With some of the world's biggest and best colonies found on our coastlines, Britain is internationally important for seabirds. 90% of the world's Manx shearwaters, 68% of the world's northern gannets, and 60% of the world's great skuas are found in Great Britain and Ireland.
Although this year things are looking good, Britain's seabirds have been having a hard time recently. Last year, kittiwakes, Arctic terns and Arctic skuas had a terrible breeding season. In the far north of the UK, almost no chicks were reared to fledging. Guillemots, puffins and razorbills also suffered.
Initially, the problem was thought to be caused by their food. Many seabirds feed on sand eels. Although not really exploited for human food, sand eels are used for animal feed and fertilizer so they are a target for industrial fishing.
This fishing, some argued, was affecting seabird levels, especially that of auks because they take sand eels in deeper water. Because of this, fishing for sand eels was banned in the North Sea, and the seabird populations improved.
But when the seabird population subsequently crashed again, it became clear fishing could not be the major cause. Research carried out points to other factors.
The Centre for Ecology and Hydrology carried out studies on the Isle of May. It found links between declining kittiwake productivity and higher local sea temperatures. For sand eel eggs to hatch into larvae in winter, they need the right sort of plankton, at the right time. But higher winter sea temperatures change the composition of the plankton, so the right sort of plankton wasn't available for the sand eels.
The Sir Alister Hardy Foundation For Ocean Science recently announced a staggering 70% reduction in the biomass of zooplankton in the north east Atlantic since the 1960s. On top of this, the cold water zooplankton Calanus finmarchicus is being replaced by a warmer-water species, Calanus helgolandicus.
This is changing the range of animals such as basking sharks, turtles, several species such as sunfish and swordfish and invertebrates such as octopus and squid. It's also possible that climate change is responsible for the population explosion of pipefish in the past five years, which seabirds mistake for palatable prey, resulting in chick deaths and starvation.
According to BirdLife's Climatic Atlas of Breeding Birds, which scopes the impact of various climate scenarios, "five seabird species (which spend some or all of their lives at sea) are projected to 'lose suitable climate' (and thus habitat) and therefore likely to suffer extinction from the UK: Leach's petrel, Arctic and great skuas, red-throated and black-throated diver."
It might also be to do with what's happening to the birds when they are elsewhere in winter.
Herring gull numbers have declined by more than 50% in the last 25 years. The RSPB says the boom in urban gull populations has masked an overall decline in herring gulls nationally. Surveys carried out on the Isle of Man show there was a 28% drop in the number of breeding herring gulls between 1985 and 1999.
Their decline could be linked to the decline of the fishing industry, because traditionally they have fed from the discards from trawlers. Their eggs and young are also vulnerable to foxes and rodents and they may be losing out to other species, particularly the lesser black-backed gull.
Thankfully, there are some success stories. Seabirds on the Farne Islands had a successful breeding season last year. The internationally important population of shags there had their best breeding season for over a decade.
The seabird colonies in Wales have remained largely stable and in Shetland, where I've spent a lot of time lately, numbers of Arctic terns are higher than they have been for many years. Of course we'll have to wait for the results of the breeding season before we know for sure.
Let's hope for some more happy news like this soon. Overall, it's a complex and dynamic problem and one that we should be open-minded about, while looking at all the different influences to try do something positive for seabirds in Britain.
It's also worth remembering that seabirds are long-lived so they only have to produce two young in a lifetime in order to maintain a stable population. So long term these bad years may not be such a problem.
More information about Britain's seabird colonies:
- The National Trust Farne Islands
- Manx shearwaters on Skomer
- Manx shearwaters on Bardsey
- Terns on the Skerries
- Ynys Feurig, Cemlyn Bay and The Skerries
- South Stack Cliffs
- Cemlyn Nature Reserve
- Gannets on Grassholm
© MMIX~RS~q~RS~~RS~z~RS~22~RS~)
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It's really good news to hear that some colonies had a good breeding season last year; it's been so worrying how bad a time they've been having lately. I think that the problems seabirds are having really illustrates why conservation can't be narrow-minded; one species can't be saved unless the whole food chain is protected; however much we try to preserve one habitat, it won't be safe unless the whole planet is healthy. That is a sobering thought.
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I read this article with great interest and saw the program tonight, and having been at South Stack this weekend, agree with Simon that sea birds are Great.However having been to St Bees Head, 100+ miles up the Coast at Easter (April) there was very little to see, other than Gulls and a few Shags. Can someone explain, the difference, I can't see why St Bees would not be equally attractive to sea birds, than South Stack, but then I'm not a Bird?
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I live in a small town in Lancashire and when we first moved here 20 odd years ago we used to see lots of different types of Gulls but now there are only one or two pairs around and they are small with black heads, not the herring gulls which were here in great numbers. Where would they nest if they are at leasat 50 miles from any cliffs?
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I have listened to both Kate and Simon suggesting that the lack of breeding success in seabirds is due to global warming causing a crash in the sand eel population. I don't believe that this is a proven fact, there is evidence to the contrary, and a truly scientific approach would be to base one's theories on observable facts. While I am sure that there IS a crash in sand eel numbers in places, I think that it is debatable whether this is due to global warming rather than some other more obscure cause.
Langstone harbour, on the south coast, has traditionally been a source of sand eels, which local fishermen have relied on, for many years. This harbour is relatively shallow and is one of the most southernmost stretches of seawater in Britain. Although I have not taken its temperature, I am sure that it must be several degrees warmer than more northerly stretches of sea. In spite of all this though, local fishermen tell me that the harbour is still thick with sand eels, and I have seen bins full of them in their boats, as evidence. Surely if warming is a cause of sandeel crashes, they would have become extinct in this harbour years ago?
Somewhere here the theory of global warming is not working, or are the Langstone sandeels a different species?
I am very wary of glib explanations of natural phenomena, I think the evidence needs to be very carefully examined, and in my opinion the exception does not prove the rule - it disproves it. It is too easy to use an accepted fact, such as global warming, and use it as a blanket excuse to cover everything else.
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Simon Kings staement about the decline of The sandeel does not take into account the industrial fishing for this species taking place in the north sea, Denmark have been particularly busy in this respect
using what is known as silk stocking mesh to target this species, just imagine what else they catch :( breacuaig
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I go birding at Rye Harbour where the Sandwich terns seem to be having no trouble finding sand eels to feed their young with - every bird that flew past on Monday had a large sand eel.
I understand the evidence for global warming but why would the Rye Bay sand eels be so unaffected.
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Climate change could just be a red herring for overfishing -
Most people accept that the North Sea has been subjected to the most appalling overfishing. Whitefish stocks, such as cod and haddock, have collapsed and the mackerel and herring fisheries are all but commercially extinct.
Under normal circumstances the removal of whole rafts of large predatory fish would allow room for species such as sandeel, the favoured prey species of these fish, to increase their numbers dramatically, but this is not the case.
And why is this? Well, the sandeel fishery has now become by far the biggest single-species fishery in the North Sea, with landings accounting for one-third of all fish landed. The vast majority of this catch is landed and processed in Denmark. Such fundamental changes in the fabric of the marine ecosystem are what ecologists refer to as 'fishing down the food web'.
Since 1977, total yearly North Sea sandeel catches have fluctuated around 600,000-800,000 tonnes, but since 2003 catches have crashed dramatically to between 200,000-300,000 tonnes. The collapse of the fishery was particularly severe in the Norwegian economical zone with a 95% reduction in landings in 2005.
You will not have eaten a sandeel knowingly (unwittingly perhaps as a fish-oil supplement), so what exactly are sandeels used for? The sandeel is an exceptionally oily fish and is harvested for the rapidly expanding fish-oil and fish-meal industries and used in everything from food for farmed salmon to animal feed and health supplements. At one stage sandeels were even used to fuel Danish power stations. And demand is set to increase.
Recent forecasts by the FAO (UN Food & Agriculture Organisation) indicate that aquaculture and its insatiable appetite for fish-oil, will dominate world fish supplies by 2030, fuelling pressure for a high level of industrial sandeel fishing in the North Sea. It takes, for example, 4kg of wild caught sandeel to produce 1kg of farmed salmon.
This does not bode well for the marine species in the North Sea that depend on sandeels for food. Many scientists and ecologists believe that the recent disastrous breeding seasons for many of Europe's seabird colonies can be directly linked to the industrial fishing of sandeels in the North Sea.
As early as 1997, two respected Danish fisheries scientists - Henrik Gislason and Eskild Kirkegaard - were highly critical of the North Sea sandeel fishery, and they concluded that "it cannot be ruled out that (sandeel) fishing could adversely effect (sic) the breeding success of the birds. It would therefore be precautionary to close areas to fishing until more is known about sandeel stock structure and interactions between sandeels and seabirds".
And a report published by the International Council for Exploration of the Seas (ICES) suggests that "the amount of industrial fish species taken by fishermen in the North Sea appears to leave little for seabirds and marine mammals".
It would not be unreasonable then to suggest that the overfishing of sandeel stocks may represent the single greatest threat to seabirds in the North Sea, especially in the breeding season when seabirds forage close to their colonies.
And it is not only the seabirds that are suffering. Studies into the diet of common dolphins, grey seals and harbour porpoises in Scottish waters have shown that they feed mainly on sandeels in the spring and early summer. The affects on these species if they cannot find sandeels to eat at this time of year can be disastrous. For example, spring is a critical time for dolphins and porpoises in terms of energy requirements. Some of the lowest sea temperatures occur in the North Sea in March, putting a great strain on dolphins and porpoises as they require the thickest blubber layer to limit heat loss at this time. In addition, young animals are weaned and become independent foragers in spring, placing them at the mercy of changes in sandeel availability.
Ironically the long-term overfishing of sandeels in the North Sea may also inhibit a return to the former healthy status of predatory fish stocks such as cod and haddock, as these stocks can only recover if there are sufficient prey fish for them to feed upon. This is what ecologists refer to as a 'negative feedback loop', a vicious circle of exploitation that renders an ecosystem incapable of a recovery to anywhere near its former productivity.
It may not yet be too late however, but our attitudes and tolerance to an industry that has got perilously close to destroying the very fabric of the North Sea must change dramatically. No longer can we view the commercial fishing industry with the romantic notion of hard working fishermen risking everything to put fish on our plates. It must now be seen for what it is, a ruthless, efficient, hi-tech industry of destruction, that is prepared to wipe out whole species for profit with almost no long-term consideration for the health of the marine environment.
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Simon - What about Filey, Bempton and Flamborough? good news or bad re
numbers. Is it also true Guillemots, normaly sociable birds are turning
on unattended neighbours chicks in a bid to secure their owns survival?
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Thank you, marineBlueplanet, its depressing news, but you do explain the cause of our small south coast harbours and inlets still having sandeels, while the open sea areas to the north don't have them any more. The easy global warming explanation has never made sense to me, there is too much evidence to the contrary.
Is it too much to ask, I wonder, if the pro's and cons of this issue could be brought to the attention of Kate, and Simon, and re-aired, for the sake of accurate public information.
The global warming theory is looking dangerously fallacious, Springwatch can inject some truly scientific thinking by examining the evidence rather than trotting out undigested conclusions not based on factual observations. Now that really would be educational!!
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I do partly agree with marineblueplanets comments saying that the overfishing of the baitfish industry is likely to be responsible for the decline in seabirds and other marine life that feeds on it. However I feel that it is unfair to blame the overfishing on the Aquaculture industry.
While it is true to say that aquaculture, more specifically the production of fish for human consumption utilises sand eel and other bait fish in its feed and that it is also unsustainable to produce certain species of fish in captivity; it is folly to suggest that aquaculture is to blame for the decline in bait fish in the oceans.
Lest we forget that we have been removing baitfish from the sea mainly for use in the animal feeds industry for a very long time and as long as there is competition in the agriculture sector there will be a need for use of baitfish in animal feeds. There is of course no evolutionary benefit or reason to feed fish to cattle, sheep and poultry. When was the last time you saw a chicken stooping down from the sky to scoop a trout out of a mountain lake? or a sheep bouncing around in the highland rapids with its head under the river only to be seen emerging with a salmon in its jaws?
I jest you not, this may sound funny but the fact is that cattle, sheep and poultry simply don't eat fish! The only reason that fishmeal and oil is added to animal feed is to make the animals grow faster. This is because fish protein is the most digestible form of protein on the face of the planet, ours and other animals bodies can convert the energy in fish into muscle faster than any other form of protien.
Of course the animal production industry will have you believe that its for the health of the animals and that the use of fish oil in animal feed passes on this goodness to the human consumer and therefore eating eggs impregnated with omega 3 fish oil is good for you. This is nonsense! Most animals convert fish oil back into lower forms of omega fatty acids when they consume it and therefore by the time it gets to your stomach it is no more use than cereal. If you want to gain the benefits of omega 3 fish oils there is simply only one healthy and natural way to get it - eat fish!
Yet the food production industry and feed companies insist on piling tonnes of fishmeal and oil into the animal feeds that produce the meat we eat because its more profitable.
The animal producers know that if they feed their animals with feed that includes fishmeal / oil, their animals will grow faster, they will bring more animals to slaughter quicker and therefore they will MAKE MORE MONEY!!!!!!!!!
The feed industry insist on including fishmeal in their animal feeds because farmers will buy this product at a higher price than feed that doesnt include fishmeal for the very reasons already stated and therefore the feed producers will MAKE MORE MONEY!!!!!!!
Aquaculture is another story all together. At this time the only efficient means of producing the marine carnivorous fish we love to eat, like cod, in captivity is to feed it with feed containing fish because, strangely enough cod in the wild eat fish and have done throughout their evolution.
This DOES NOT make the farming of carnivorous fish species a sustainable method of farming food for our mouths. However, if the use of fishmeal/fishoil in other animal feeds was banned or seriously curtailed then more fishmeal would be available to aquaculture at least until a synthetic or organic equivilent of fishmeal/oil can be found.
Once again, as with the likes of the fisheries themselves; until the FAO/WFO and governments get a handle on this complete misuse of the worlds valuable resources and start thinking about conservation over profit the situation is not going to get any better.
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