Gull do not breed in the vicinity of Skogsøy so it is easy
to spot the migrants....The first birds can be seen in early March and
the majority pass during April. There are two peaks to the autumn
migration - one in late July / early August and another much later in
the season in October / November.
It would seem that this species is noted in larger numbers at
Utsira than at Skogsøy.
The blue line shows number of visits, the orange one the number of
visits when Black-headed Gull have been recorded and the green one
(numbers on right hand axis) shows the maximum
numbers I have recorded in any three day period.