Náttúrufræðingurinn - 1969, Blaðsíða 45

NÁTTÚRUFRÆÐ I NOURINN
39
S U M M A R Y
The possible dispersal of seed by snow buntings to Surtsey in 1967
by Sturla Friðriksson and Haraldur Sigurðsson
Distant islands must to a great extent owe tlieir plant and animal life to
long distance dispersal of living material. The role played by birds in such
a transport has been a matter of some dispute among biologists.
It was suggested that the almost sterile liabitat of the new volcanic island
of Surtsey might offer a unique opportunity for studying the possible role
birds play in transporting plants and lower animals across wide stretches
of ocean.
Surtsey being the southernmost dryland of Iceland might become the first
landing place for migratory birds arriving in the spring from European
countries. For this reason migration of birds to the island was rccorded and
a variety of birds were collected on Surtsey as they arrived during the period
March 31 to May 12 1967.
The birds cauglit were identified, sexed, and weighed. They were then
closely searched for any possible seeds or other organisms which might be
attached to the exterior of the body, after which the birds were dissected and
their alimentary tract cleaned of content. This content was then measured by
volume and weight and inspected for organisms. 11' there were seeds ])resem
tliey were identified and tested for germination. Finally the grit from the
gizzard was inspected as its minerals or rock types might reveal its origin and
thus the location where the last intake of food had occurred.
From the total number of 97 birds of 14 different species, none of the birds
carried seed on tlieir exterior. A few birds, however, carried nematodes or
other parasites which are not of direct interest in the transport of colonizing
organisms.
Of the total birds caught 32 were snow buntings of the nominate race which
differs from the Icelandic race. Of these, ten individuals liad in addition to
grit seeds in their gizzard.
In Table I these snow buntings are listed witli information on measure-
ments of birds and content of their alimentary tract. The ten birds carried
with thern 87 seeds, the majority of wliich seemed viable and of which two
were grown to maturity. The plants grown were those of Polygonum persi-
caria L. and Carex fusca All. (C. Goodenowii Gay). (Table II.)
Grit from the ten snow buntings was examined under the petrographic
microscope. The number of grains identified in each thin section ranged l'rom
97 to 511. Table III shows that the number of mineral or rocktypes is high
but the grit grains can, however, be divided into tliree clearly separated
groiij)s: basaltic ash from Surtsey, metamorphic rocktypes and younger sedi-
ments.
The ash from Surtsey stands out clearly in the microscope as angular of