Tweeters,

I am inclined to agree with Stuart MacKay's point of view about the
"Scottish seabird disaster".

I am not familiar with the long-term history of seabird populations,
or breeding success, in northern Scotland or in the larger North Sea
area. However, if the situation is at all similar to that in the
Pacific Northwest, widespread breeding failures affecting several
species should not be at all unusual. In Washington, Oregon, and B.C.,
there have been years of almost total breeding failure in Common
Murres (="guillemots") and other species, usually associated with the
"El Nino" phenomenon. This periodic change in sea conditions results
in warmer than normal water temperatures, associated with dramatic
drops in the abundance of some key fish species, and a resultant
scarcity of food for fish-dependent seabirds, which causes breeding
failures. One or two years of unsuccessful breeding are usually
followed by a return of normal cold-water conditions, a return of the
usual fish species, and a resumption of successful breeding.

It may be that Britain does not have such regular, predictable cycles
of warm water and cold water as the Pacific Northwest, and that
seabird breeding failures are less frequent and more alarming than in
the Pacific Northwest. However, the situation sounds suspiciously like
that close to home.

Most seabird species-- this includes gulls, terns, alcids, and
tubenoses, at
least-- are very long-lived, and are adapted to deal with periodic,
even frequent, breeding failures brought on by food shortage. For many
of these species, 90% or more of the adult birds will be alive next
year, and will attempt to breed again then, probably with greater
success. A total breeding failure for several species in one year may
be a cause for concern, but it is not a "disaster", nor is it
necessarily evidence for global warming.

The above statements need to be viewed in a broader context. If
breeding failures continue for 2 or 3 years in a row (as they
sometimes have), there is much greater cause for concern. If the food
shortages are due to overfishing rather than climatic changes, this is
also a serious cause for concern. (This has also happened, as pointed
out by Stuart.) Also, if the average ocean temperatures are increasing
over a period of decades, this is cause for alarm. It looks like this
may well be true in some areas. The net result could be simply that
some seabird species end up shifting their range father to the north.
However, those species that breed largely in the Arctic or subarctic
(e.g. Dovekies and Thick-billed Murres) may not have many "farther
north" areas to move to.

The factors affecting the numbers and breeding success of seabirds are
complex, imperfectly understood, and are somewhat different for each
species. However, I agree with Stuart that it is premature and
irresponsible to label a one-year breeding failure a "disaster". This
idea may result simply from the fact that many people do not realize
that periodic breeding failures are a normal part of the breeding
ecology of many seabird species in many parts of the world. On the
other hand, an event that causes major mortality of adults, such as a
serious oil spill, will lead to a long-term reduction in populations,
and in my view, deserves the "disaster" label.


Wayne C. Weber
Delta, BC
contopus at telus.net




----- Original Message -----
From: Stuart MacKay <stuart at blarg.net>
To: <tweeters at u.washington.edu>
Sent: Friday, July 30, 2004 8:16 PM
Subject: Re: Scottish seabird disaster


> There are few points which should be taken into consideration when
> reading this article.
>
> 1. In the late 1970s and 1980s there was a similar pattern of poor
> breeding success in seabird colonies in the Orkney and Shetland
> Islands. Some arctic tern and kittiwake colonies had poor success
for
> nearly 10 years in a row.
>
> The "cause" was supposed to be the large industrial fishery for
> sandeels - the main food source for a lot of seabirds in the area.
> Eventually the fishery was severely restricted. The year following
the
> ban the seabird colonies had good breeding success.
>
> Was this the root cause? Possibly, however it could also have been a
> coincidence since there was no direct evidence of the fishery
causing
> harm. There was no direct evidence as most of the fishery was taking
> place far offshore whereas most seabirds foraged relatively close to
> their colonies. Also several colonies in the Orkney and Shetland
> Islands and in nearby Caithness (on the Scottish mainland, where I
am
> from) were not showing the same level of decline. Some colonies were
> stable if not increasing.
>
> 2. Seabirds are long-lived and such patterns of poor success may in
> fact be "normal" - though they are alarming. Research has been
carried
> out in northern Scotland for the past 40-50 years with more
extensive
> datasets available since the late 1970's. What the natural cycle is
> still unknown.
>
> 3. Guillemot numbers in particular and most seabird species in
general
> are at an all time high - as far as can be ascertained. Numbers of
> guillemots in particular have exploded in recent years. This is
mostly
> likely due to the decimation of the top predator fish resulting in
> booming numbers of species such as sand-eels. The decline in food
> supply could be linked to general imbalances in the marine
environment
> caused by large-scale overfishing.
>
> 4. The numbers of bird affected as quoted in the article are small.
> 172,000 pairs of guillemots are a small, though not insignificant,
> percentage of the population. There are several colonies in northern
> Scotland with more than 50,000 pairs. Also 16,700 pairs of
kittiwakes
> is tiny. There are probably a couple of million breeding pairs of
> seabirds in northern Scotland.
>
>
>
> After the first "disaster" was averted the seabirds were not the
only
> ones saved, so were more than a few reputations of scientists who
had
> been fore-telling disaster with the first priority being of course,
> more money for research. There is a history of accentuating the
> negative when it comes to environmental problems of breeding
seabirds
> in the North Sea area. So as with politics, you should always be
> careful to "follow the money".
>
> The changes in the North Sea due to climate change will be bad.
> Overfishing and pollution has made things worse. However the data is
> not conclusive that global warming or overfishing is the direct
cause.
> We simply do not know.
>
> The downside to all this is that hype and scare-mongering will
result
> in scientists get treated as Cassandras and nothing will get done.
>
> Stuart
> --
> Stuart MacKay, Seattle, WA, USA
>