Pomarine
Skua is a relatively scarce, though regular spring migrant at
Skogsøy with a peak sometime in the second half of May.
Large numbers can be seen under strong onshore winds but this is a
relatively rare event. Often this species comes past at close range
following the coast and the sight of these fantastic birds with their
remarkable tails is a real experience. As with all locations the
numbers passing vary
enormously and it seems only a small fraction of the
population happen to pass Skogsøy - this species is
probably
of more birding interest than any monitoring studies at this locality.
It seems that Skogsøy gets as many poms as most other places
and
seems to do better than Utsira, at least during the spring. It even
appears to out-perform the Shetland Isles where in most springs only
singles are recorded (there have been more than 100
individuals recorded annually there during only four years).
Although I may have been lucky I have recorded this species on
approximately half of the "in season" visits.
The following diagram shows the maximum recorded in a given three day
period (green line, scale on right hand axis). In order to give an idea
of the frequency of observation observer effort is presented as the
blue line (number of visits) and the orange lines (number of days the
species was recorded). More comprehensive data is available on the
Skogsøy downloads page.
Number of Pomarine Skua observed at Skogsøy by week number. Source: artsobs
The species is predominantly a spring migrant at Skogsøy
with generally few noted in the autumn. One
of the best days to see this species is 17 May - the Norwegian
national holiday; this holiday is taken very seriously by the
Norwegians so it is not often that I find other birders at
Skogsøy on this particular date.....
Pomarine Skuas populations are poorly monitored
throughout their lifecycle; spending the breeding season wandering the
far north and the non-breeding season living a pelagic lifestyle out in
the Atlantic.
One thing I have noted is that this species often tends to pass early
in the morning, and on days when Arctic Skua are also passing there
regularly seems to be something of a changeover around 0800 after which
few "poms" are seen. This shows up well in the diagram below, only days
where both Pomarine and Arctic Skua passed have been included. Why is
this and do the two species really have markedly differing migration
strategies? It should be noted that the amount of data this diagram is
based on is somewhat limited.
Record:
The record day count is 80 individuals (late May).
Weather:
There seems to be a slight tendency for more to be seen during
headwinds, but they can also be seen during southerly winds.
References:
Tveit, B.O., Mobakken, G. og Bryne, O. 2004 Fugler
og fuglafolk på
Utsira.
Utsira Fuglestasjon
Ellis,P., Harvey, P.,Heubeck,M.,Okill, D., Osborn,
K.,Pennington,M.,Riddington, R. Birds
of Shetland.
2004.
