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Nature in Wales


Vol. 11, no. 1 March 1968

Visible autumn migration at St. David's Head

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Most of the sea-watching was done in the morning, 171 hours
being before 9.00 hours and only 51 hours after mid-day. Move-
ments of most seabirds were apparent shortly after dawn, quickly
built up to their maximum within an hour or so, and had usually
begun to wane by 9.00 hours. Generally only small numbers
passed after 11.00 hours. Almost all the seabird movement was
south-westerly (i.e., right to left). A much smaller number of
seabirds flew in other directions; these birds are sometimes recorded
in this paper as "flying to the right" as their direction was less
consistent than the main south-westerly passage and varies between
north and east. In general, the direction of movement was inde-
pendent of tide and of wind direction, and passage occurred at
all times of day, though mostly in the morning. Though these
observations suggest true migration, P. Davis (personal communi-
cation) points out that there is little evidence that many seabirds
pass south through the gap between Northern Ireland and Gallo-
way. Possibly the seabirds passing St. David's Head, and those
observed on passage elsewhere in the Irish Sea, are blown there by
strong south-west or south winds, and subsequently evacuate to
the south through St. George's Channel. However, the feeding
movements of seabirds are not well known and it is possible that
some of the movements observed were associated with local birds
feeding. The evening passage of Manx Shearwaters, noted in
August, may be an example of this.
In addition to the species detailed below, other seabirds such
as Shag (Phalacrocorax aristotelis) were frequently seen but no con-
sistent direction to their movement was noted.
Divers. Eleven divers passed south-west between 10th September and
1st December, while only 1 was seen flying in the opposite direction. Most
passed in the early morning flying low over the sea but a party of 4 on 30th
September was flying at a height of 80 feet. None was specifically identified
but most appeared rather pale and were probably Red-throated Divers (Gavia
Shearwaters. In August there was a considerable south-westerly passage
of Manx Shearwaters (Procellaria puffinus) mainly in the late evening. The
highest count was 231 between 18.30 and 19.00 hours on 22nd August. This
was the only evening peak noticed in any species and these birds, passing in
small flocks of up to 20 or 30, may have been going to return to their burrows
on Skomer or Skokholm after dark.
The only shearwaters definitely identified as Manx in September, occurred
during force 5 north-westerly winds on the 17th when 230 passed between 6.00
and 7.00 hours with smaller numbers later in the morning. A Balearic Shear-
water (P. p. mauretanicus) was seen on 10th and 2 on 17th September and a
large unidentified shearwater on 23rd. All shearwaters were heading south-
west and flew low over the sea. No shearwaters were seen after September.
Fulmar (Fulmarus glacialis). During August a total of 22 flew south-west and
10 flew in the opposite direction. During September, in 8 hours of sea-watching,
up to 17th, 54 flew south-west, mainly as singles or twos, and only 3 passed to
the north-east. None was seen after 17th September.
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