Náttúrufræðingurinn - 2021, Side 23

Tímarit Hins íslenska náttúrufræðifélags
23
Ritrýnd grein / Peer reviewed
Vöktun súlustofnsins
Fylgst hefur verið með stærð súluvarpa
og breytingum á þeim lengur en vörpum
annarra sjófuglategunda hér á landi.
Hingað til hafa íslensk súluvörp verið
vöktuð fyrst og fremst með ljósmynda-
tækni, fyrst þegar bandaríski herinn á
Keflavíkurflugvelli tók loftmyndir af
Eldey árið 1953.9 Þar áður var um beinar
talningar að ræða eða áætlanir.
Til er mat á einstökum súlubyggðum
frá ýmsum árum á 19. öld43 þótt draga
megi í efa hve áreiðanlegar þær tölur
eru. Fyrsta matið fyrir íslenska súlu-
stofninn í heild er að finna hjá Gurney44
sem taldi hér vera 13.600 varppör í sjö
byggðum árið 1913 en sagði tölurnar
þó ekki með öllu ábyggilegar. Tuttugu
árum síðar voru metin um 13.600 pör í
sex byggðum á Íslandi6 eða sami fjöldi
og Gurney gaf upp. Fyrsta skipulagða
heildartalning á íslenska súlustofn-
inum fór fram árið 1939 og voru þá álitin
13.732 varppör í landinu.7 Síðasta birta
matið fyrir íslenska súlustofninn er frá
Arnþóri Garðarssyni sem taldi hann
nema 37.216 varppörum 2013–2014.5
Stofninn hefur því nær þrefaldast frá
því fyrsta áætlunin var sett fram í byrjun
20. aldar. Hann virðist lítið hafa breyst
fyrstu áratugi þeirrar aldar.
Árið 2017 var súluvarp í Eldey í fyrsta
sinn talið með dróna og reyndust setrin
vera 14.982.45 Árin 2013–14 voru þar
14.810 setur samkvæmt loftljósmyndum
úr flugvél.5 Samsvörun er því ágæt.
Þessi nýja tækni verður vonandi notuð
við vöktun annarra súlubyggða þegar
fram í sækir, enda eflaust bæði ódýrari
og ekki eins tímafrek og ljósmyndun úr
flugvél. Drónar verða vonandi líka not-
aðir í framtíðinni við vöktun annarra
sjófuglastofna. Fyrir utan talningar í
þekktum vörpum er full ástæða til að
fylgjast með nýjum stöðum þar sem
súlur geta numið land, svo sem og á
Hornströndum, sem hluta af almennri
stofnvöktun.
SUMMARY
Northern Gannets attempt to
re-colonize former nesting area
Although far away from present-day
colonies, Northern Gannets are seen
now and then in flight off Hornstrandir
(NW-Iceland), like elsewhere around
Iceland.21-22 The current paper describes
the available observations on a possible
breeding attempt at Langikambur at the
Hornstrandir Nature Reserve (Figs 1–2).
First indication of nesting is from
2014 when a photograph was taken of
what later turned out to be a Gannet
nest (Fig. 3). In the summer of 2016, a
Gannet was first seen on nest at Langi-
kambur (Fig. 4) while nest building was
also noted in 2017–2020 (Figs 6-8), all
these years at exactly same place. This
site, which is on a dyke extending about
230 m out from the mainland, is located
about 280 km from the nearest Gan-
net colony in NE-Iceland (Rauðinúpur
on the Melrakkaslétta peninsula), and
around 370 km from the nearest colony
off Iceland’s SW corner (Eldey island),
cf. Figs 1–2. This is the first time since
the end of the 17th or early 18th century
that Northern Gannets show signs of
breeding in this part of Iceland. His-
torically, Gannets bred on Súlnastapi
stack, which is only about 500 m from
Langikambur.14,15
No eggs have been recorded in these
new nests so far but hopefully these are
the first steps towards a new Gannet
colony for Iceland. The former colony
on Súlnastapi is said to have been dec-
imated by Icelandic fishermen about
two centuries ago.15 That site is thought
to take its name from súla, which is the
Icelandic name for the Gannet. Súlna-
stapi as a place name is known at least
as far back as to year 1327 which may
indicate Gannets nested there as early
as in the 14th century.31-33
It is important to document the
establishment of new seabird colonies
as detailed as possible as part of general
population monitoring. At present nine
colonies of Northern Gannets exist in
Iceland (sometimes counted as eight,
as two of them, Stóri-Geldungur and
Litli-Geldungur in the Westman Islands,
are often counted as one, Geldungur,
being close to each other).5 Three of
these sites are relatively recent, first col-
onized in the 1940s and 1950s; Skrúður
(E-Iceland),34 Rauðinúpur on the Mel-
rakkaslétta peninsula (NE-Iceland),35
and Stóri-Karl by Skoruvíkurbjarg on
the Langanes peninsula (NE-Iceland).36
In addition, at least four colonies were
in use in the past but are now extinct
besides Súlnastapi. These colonies were
located at Geirfuglasker off Reykjanes
peninsula (SW-Iceland),37 the stack
Kerling in Skagafjörður38-39 and Gríms-
ey island (both in N-Iceland),6,40 and
Máfadrangur stack (S-Iceland).1,10,12,41
Gannets are known to frequent cer-
tain roosting sites, but not breed. Such
sites include Ingólfshöfði headland
(SE-Iceland), the stack Karl or Karlinn
off Reykjanes peninsula (SW-Iceland),
Svörtuloft bird cliff on the Snæfellsnes
peninsula (W-Iceland),1,11 Dyrhólaey
peninsula, the stacks Lundadrangur,
and Reynisdrangar (all in S-Iceland).13,42
Counts for some Icelandic Gannet
colonies date as far back as the 19th cen-
tury.43 The Icelandic population was
first estimated in 1913,44 but the first
systematic census using direct counts
took place in 1939.6 Arnþór Garðarsson
has monitored the Icelandic Gannet
population for the last four decades, the
most recent census giving 37.216 pairs
in 2013–2014.1–5 This is the longest mon-
itoring series for any seabird species
breeding in Iceland.