White-billed
Diver - Gulnebblom
- Gavia
adamsii Vitnäbbad
Islom - Hvidnæbbet Lom -
Jääkuikka - Plongeon
à bec blanc
Above and below: Adult White-billed Divers (Yellow-billed Loon) heading
north past Skogsøy, May 2016
The
White-billed Diver is a regular migrant in both spring and autumn
at
Skogsøy, although appears more numerous in spring when it is
the
second commonest diver species. The first birds turn up towards the end
of April, though most pass in May with a peak in the first half of the
month; occasional birds are observed
into June. Daily counts of less than 10 are the norm but during the
peak passage period double figure counts are not
unusual - the record count is over 40
individuals in one day.
During the autumn White-billed Diver appear to be a lot less regular
with occadional singles being noted. This could indicate some kind of
loop migration whereby the autumn migration takes place further to the
west.
The diagram below shows the maximum counts per 3-day period using my
own sporadic and non-systematic counts. The blue line shows the number
of visits and the orange the number of days White-billed Diver have
occured - the two are almost concurrent in the first half of May
indicating that is quite normal to see this species at this time at
Skogsøy. The green line shows the maximum count per three
day
period.
The above diagram is somewhat out of date but still shows the pattern
of occurrence and liklihood of seeing this species
Number of
White-billed Divers seen at Skogsøy by week number. Source:
artsobs
During the spring the vast majority of birds are adults and they often
pass
at close range.
Based on my 8 visits during the spring of 2005 well in excess
of
200 individuals are estimated to have passed Skogsøy. This
estimate was derived using the same method as Folvik and
Mjøs
used (see references).
Numbers of White-billed Diver at Skogsøy far exceed those at
Utsira and in the Shetlands and relatviely few are observed further
south so this species either has a secret wintering ground in the North
Sea, which I consider to be unlikely, or, more likely they come in from
the west, "over the top" of Scotland, hit the Norwegian coast and head
north along it.
Large numbers of White-billed Diver are observed at Slettnes each
spring as they head east. The number of sightings off Shetland also
seem to be increasing as the numbers at Skogsøy also appear
to
be doing. Trends
in the population are poorly known as is the location of the species
wintering grounds.
Spring
migration in Alaska is 15 May-9 June; in Canada 28 May-15
June. Fall migration in Alaska is late August-early October,
in Canada late Aug and Sept.; along Pacific coast of Asia is
October. (Michael North pers. comm.)
Sometimes
the White-billed Divers pass in small flocks, May 2020
Migrating White-billed Divers, May 2020
Migrating White-billed Diver, May 2020
Migrating White-billed Diver, May 2020
The subject of being out in a boat to watch White-billed Divers is a subject that often comes up at Skogsøy......
Here from April 2018
References Folvik, A., Mjøs,
A.T. 1995. Spring
migration of White-billed Divers past southwestern Norway.
British
Birds 88: 125-129
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.
