Eider numbers on the decline

The population of eider ducks in the isles has declined dramatically over the last 30 years, with a marked decrease between 2009 and 2012, when the latest survey was carried out.

Eider ducks are vulnerable to inshore oil pollution, and the Shetland Oil Terminal Environmental Advisory Group (SOTEAG) has monitored their numbers since the oil terminal was built.

Surveys in the 1970s found flocks used the same headlands or offshore skerries each year, where they could feed, roost ashore and find shelter in varying wind directions.

The population was estimated at 17,000 birds in 1977, but the Esso Bernicia oil spill in winter 1978/79 and an unexplained die-off in the main Bluemull Sound wintering flock in 1979/80 reduced this to 12,000 by the early 1980s, with a further decline to 6,000 by 1997.

The Braer oil spill in January 1993 and oiling incidents around Bressay between 1992-96 from eastern European fish factory ships contributed to this decrease to some extent, but could not account for this halving of the population. Predation of ducklings by gulls and skuas is another probable contributory factor.

Eider ducks are common in northern Britain but genetic studies suggest those in Shetland are closer to the Faroese race than those breeding in mainland Scotland, which makes them of special conservation concern.

They are resident in Shetland but make seasonal movements around the isles and shift their feeding locations in response to short-term weather conditions. However, in late summer adults become flightless during their annual moult, and by August flocks are restricted to a swimming distance of about three kilometres, and are therefore relatively easy to locate and count.

The situation became complicated in the early 2000s as increasing numbers of eiders began spending the summer near aquaculture sites. A survey in 2009 counted 5,800 birds, little changed since 1997, but they had changed their location, with 70 per cent near aquaculture sites in the inner voes.

For example, only 164 birds were counted in 2009 at “traditional” sites in the South Mainland compared to 1,580 in 1997, whereas numbers between Burra and Vaila Sound had increased from 370 to 2,650.

Eiders have generally been tolerated at salmon farms, where they feed on mussels growing on the infrastructure, and find shelter. However, there has certainly been conflict with eiders feeding at mussel lines, and while various anti-predation measures have been tried out, it is difficult to see how these could have been responsible for the loss of 1,000 birds in just three years.

One contributory factor could be increased predation by killer whales. Although few attacks on eider flocks have been witnessed, they have resulted in the death of up to 50 birds in a matter of minutes – this has happened in Faroe.

The 2012 survey was funded by the Sullom Voe Association Ltd, and David Parnaby (FIBO), Penny and Sheila Gear (Foula), Rory Tallack and Howard Towll (Shetland Amenity Trust) and Newton Harper (RSPB) participated. Thanks also to boatmen Jim Dickson, Victor Gray, Jerry Ramsay, George Williamson and Jonathan Wills.

The next census is planned for August 2015 and hopefully there will be no further decline in numbers to report then.

Martin Heubeck and Mick Mellor

11 comments

  1. Winnie. Tribe

    I blame the blackback gulls for the decline in lots of our breeding birds

    Reply
  2. David Spence

    Winnie, the biggest threat to wildlife and this planet is human beings. Especially those who only think of themselves, greed and profit at all costs (typical trait of capitalism).

    If humans continue with the mindset of only looking after their own as a consequence of a system purely designed to destroy no matter what (the monetary system – the crown of capitalism) then nature, quite rightly, will take matters into a situation where (with any luck) nature will obliterate any existence that humans were ever on this planet.

    Humans (as a consequence of capitalism) are destroying the world and life on this planet (at the present rate 1 species every 2 days) at a rate faster than ever before (excluding the meteorite which caused the extinction of the dinosaurs 65 million years ago) and at the present rate again, by the year 2050 over 30% of all mammals will become extinct as a result of human activity.

    If you include this fact of mass extinction of wildlife as well as the damage we are causing to the environment, then there is going to come a tipping point where nature will put into action events which will, and there will be nothing we can do about it, eventually lead to the extinction of us as a species……and quite rightly so.

    As Keanu Reeves in the movie ‘ The Day the Earth Stood Still ‘ said ‘ I didn’t come here to save you from Earth, I came here to save Earth from you. If you live (humans) the Earth Dies, If you die, the Earth Lives ‘. Never a truer word said.

    Reply
    • Ali Inkster

      You seem to be delighted at the idea of an earth without humans David, small steps david small steps and may I be first to congratulate you in advance when you show us the way by taking that first small step.

      Reply
  3. rosa steppanova

    There used to be large rafts of Eiders in Tresta Voe, including the occasional King Eider. The distinctive mating call of the males could be heard each and every spring. Then mussel rafts were installed in the voe, and for years, day in and day out, there were the loud booms of the anti-predator warning shots, followed by frightened birds taking to the air. The ducks were driven away and now the voe is silent in spring.

    Reply
  4. David Spence

    I can remember being many, many eider ducks just off Unst, and between Unst and Yell in Bluemill Sound, and like you Rosa, the distinct call of the eider duck was heard all the time……now, the waters are silent.

    Winnie, putting my previous comments aside, I would say it was still more to do with human activity, as Rosa has mentioned, Mussell Farms as well as Salmon Farms, contributing to the downfall of the Eider Duck as well as many other species. I would not necessarily blame it on either the Greater or Lesser BlackBack Gulls being solely the cause of the decline.

    This trend is applicable to many species and not just the Eider Duck.

    Reply
  5. Christopher Ritch

    From the Shetland Nature facebook page yesterday (Bluemull sound was not silent)

    “Wow, what a day! We found a Female KING EIDER, which I like to call a ‘queen’, in same Eider flock as the wintering King, saw two White-billed Diver, the wintering drake Smew and a Glaucous Gull and an exhilarating total of seven Otters!!”

    https://www.facebook.com/shetlandnature?ref=stream&hc_location=stream

    Reply
  6. Ali Inkster

    My god david we agree on something its not just the black back that’s responsible for the decline of our many bird species, the bonxie and the scooty alan are right up there with the buggers killing everything in range. Just as well some environmentalist got them protected because soon their all that be left

    Reply
  7. Ivor poleson

    I live on the edge of Ronas voe where every spring the eider ducks gorge themselves on small mussles from the many mussel lines in the voe . Completely free from any molestation from the mussel farmers I might add.
    The eiders then head of into the hills to nest and without fail every year since ive been here bring rafts of young ducklings back to the sea in late summer. I cant remember them having a bad breading season in over 20 years.
    And without exception every year since ive lived here over the next few weeks the blackbacks and the bonxies eat them all. They also eat small gillimots ,razorbills, puffins, tirricks ,shalders , kittywakes and even the odd fulmar.
    To anyone who cares to open their eyes nature is very a very cruel place.
    If the RSPB insist on protecting swabies and bonxies I don’t know what else they expect to happen.
    Then again sadly ive never met an “environmentalist” yet who new the slightest thing about the environment.

    Reply
  8. Ali Inkster

    Yes Ivor i the UK sparrow hawks were endangered during the 70s then the city dwelling environmentalists got them protected from those nasty rural farmers, now there are 35,000 breeding pairs in the UK and the city dwelling environmentalists are now blaming the nasty rural farmers for the sharp decline in sparrows and song birds. They can’t accept that having 70,000 predators where before there were virtually none can have any effect on populations. It must be the fault of all those nasty farmers, just like we keep hearing how its the fishermens fault up here for the decline in bird numbers.The environmentalists have done a very good job in reducing fishermen and farmers numbers but have not managed to eradicate them yet, but if at first you don’t succeed then try try again.

    Reply
  9. Robin Barclay

    The comment on swabbies may not be far off the mark, but has anyone considered bonxies? The swabbie population has declined in the area I am familiar with (Noness, in Sandwick), as have other gulls, but bonxies now teem there (they previously nested only on nearby Mousa, but only started to colonise Noness in the 1970′s). Dunters nested there every year until the bonxies moved in, and now no longer nest there (neither do former nesters sandy loogs and peeseiweeps – and shalder nests have declined, as have scootie allins). Maybe they are also responsible for the reduction in gulls which nested extensively around the point of Noness. Bonxies are very predatory – not just on birds – I saw them kill two newborn lambs in different locations on the same May morning a few years ago. Maybe it is time to be less tolerant of them?

    Reply
  10. Scott Gray

    What many people fail to appreciate is the fact that there is no real wild environment in the UK. Land and wildlife management has been going on for generations. People need to decide what wildlife they want to prosper and this is managed through predator control. The sad fact for me is that the likes of the RSPB and others have put a value on top level predators like raptors above other wildlife only because they generate more income for their cause. This imbalance is a real threat to prey species. You only have to extrapolate how many polecats and hedgehogs which are seen dead on our roads, run over by cars, to understand what is happening to ground nesting birds on our hills. I for one value grouse, golden plover, snipe, etc much more than predictor species such precisely because I like to hunt and eat them. Unfortunately it is these top level predators which are used to generate income for environmental charities. Don’t be fooled the best custodians of the environment are farmers, gamekeepers. I

    Reply

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