Industrial Fishing Of Sandeels Is To Blame For Seabird Declines, Not Climate Change

By Paul Homewood

Back to that RSPB report:

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According to Yahoo:

The report went on: “The UK’s kittiwake population has declined by 70% since 1986 because of falling breeding success and adult survival.

“Climate change has reduced the availability of the sandeels they rely upon in the breeding season.

“Other species that feed largely on sandeels, such as Arctic skua, Arctic tern and puffin, are at high risk of climate-related decline.”

So let’s take a close look at puffins in particular.

The Joint Nature Conservation Committee (JNCC), published a report in 2011, based on the Seabird 2000 Census. They included two maps, showing the distribution of Atlantic puffins:

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The first thing to note is that puffins are well distributed around the British Isles. Although there are many more around Scotland, this is due to the ready availability of suitable habitats.

Waters around the the south west of Wales and Ireland are much warmer than in the North Sea off the east coast of Scotland. Yet that seems to have no effect on the puffins which live in the former.

The map below showing population change also indicates that around Scotland there has been a mixed bag where some locations have seen increases at the same time as other areas close by have seen the opposite.

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Since 2002, the puffins appear to have continued thriving in South Wales.

In 2009, the Telegraph reported:

Thousands of birds began leaving Skomer Island in Pembrokeshire over the weekend.

Unlike the rest of the UK, the number of puffins on the island has soared in recent years – leaving conservationists baffled.

The island currently has a puffin population of more than 13,500 – up from 10,000 last year – with more expected to arrive next March.

Jo Milborrow, from the Wildlife Trust of South and West Wales, said: “We’re delighted that the numbers keep growing but we don’t really know why.

We think it may be because of the increased numbers of sandeels which the puffins feed on.

And Latest estimates continue to show that puffins are thriving on Skomer.

Clearly there is no evidence here of a consistent climate change signal.

But there is a very real factor, which goes a long way to explain the decline in population in the North Sea.

Sandeels comprise a large proportion of the diet of Atlantic puffins, but since the 1970s they have been subject to heavy, industrial fishing in the North Sea, predominantly by Denmark.

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Although attempts have since been made to restrict the harvest of sandeels, the horse has already bolted.

In 2013, a study by the British Trust for Ornithology (BTO) and the Joint Nature Conservation Committee found that fishing of sandeels was still having a significant impact on the population of birds such as the Arctic tern, little tern, common tern, sandwich tern, kittiwake, common guillemot, shag and fulmar.

Significantly they also found that seabirds breeding on the UK’s western colonies were faring better than those on the North Sea coast.

One more study of relevance came in 1998, “Status of the Puffin Fratercula Acrtica on the Isle of May National Nature Preserve” by Harris and Wanless, which stated:

“The history of the puffin on the Isle of May is well documented … in 1883 there were 30-40 pairs … the population was put at 5-10 pairs in the early 1950s but in 1957-58 at least 50 pairs attempted to form a colony. This attempt was brief and unsuccessful and in 1960 there were only a few pairs.”

[The Isle of May is in the Firth of Forth, which has been one of the main areas of concern in recent years.]

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So this largest puffin colony in the UK barely existed until the 1970s when both global warming and the puffin population took off. Any population decrease since 1998 must be seen in this longer term context.

To be fair, this new RSPB study does admit that many species of birds are thriving because of a warmer climate.

Inevitably, rare species are, by definition, vulnerable to any environmental change, purely because their numbers are so small. But in these examples quoted, there is no evidence that they are under threat from climate change.

It is often claimed that animals are “forced” to migrate because the weather is too hot or not cold enough. In fact, this is usually a gross distortion of the truth. A warmer climate allows birds to populate areas previously too cold to live or breed in.

As such, the birds’ habitat range is generally expanded. When this happens, there may be a tendency to favour the new areas, where there is less competition for food. As a consequence, population levels may fall in some of the warmer regions previously inhabited.

Climate change may well see a redistribution of birds, with some species disappearing from certain regions to be replaced by others. But there is little evidence that any are under any direct threat as a result.

 

 

Footnote

There is one more study of relevance, Decline in an Atlantic Puffin Population: Evaluation of Magnitude and Mechanisms, by Miles et al in 2015.

They studied puffins on Fair Isle in the Shetlands, and found that the decline in the puffin population coincided with an increase in the numbers of Great Skuas, who just so happen to prey on the poor puffins and other seabirds.

 

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Great Skuas also like to eat other birds under threat, like Kittiwakes.

 

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It may be that the Skua population took off as a result of the increase in the number of puffins already noted in the 1970s.

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December 6, 2017 at 01:33PM

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