CHANGES IN TROMSØ AVIFAUNA AT DIFFERENT TIME SCALES
In Tromsø, N.Norway (69*50'N) we have had two weeks of beautiful winter
weather: cold, crisp and clear, with sun during the days (every day a bit
longer) and magnificent spectacles of Northern Lights in the evenings.
Fifteen man-hours got most of the snow off my roof, but the youths who did
it were by then so exhausted that they shied away from the necessity to
move the same snow once more, this time from the driveway. So my
action-radius is still quite restricted these days, and my bird year list
as stable as the snow level, although at a much lower level.
Today somebody called and reported a European Jay from his feeders, on the
large island of Senja, south of here. If you look at the available
literature, that should be a sensation, as for ex. the Norwegian Bird Atlas
has no dots at all in Troms of this resident bird, and only one in the
northern part of Nordland, the province south of here. But things change
all the time, and Jays have during the last few years gradually become more
and more wide-spread in Troms, although I have yet to see one here on the
island. (They do occur, however, also north of here, but with a gradient
of decreasing frequency from inland to outer coast)
In a paper I wrote some years ago on N.Norway as a habitat for birds I
chose 'changeability' as the one word that best described the area here. As
they say on Iceland: ' the Lord did not give us a climate, just
samples!' It may snow in every month of the year, and it may rain in every
month. Last winter, and the one before that, were easy, with little snow
and few bad storms, while this winter competes with 96-97 for the honour of
becoming the snowiest ever.
These changes occur in all kinds of different time-scales. The ravens that
cavorted over the roof of the museum when I arrived this morning, are an
example of seasonal changes. Although ravens are resident birds, we see
them in town predominantly in the winter half year, and they retreat to
quieter surroundings in the nesting season. Similarly our harbour is full
of Cormorants now in winter, but for some reason few nest around here, so
they disappear in April-May. These movements are pretty regular, but others
vary from year to year. Thrushes (Fieldfares and Redwings) stay around
until late in winter in years with bumper crops of Rowanberries, but leave
in October when there are very few berries. (This year is in between, and
there are still a few isolated Fieldfares hanging around in town.) Other
birds, the so-called invasion birds, are common one year and absent the
next: the best examples here are Great Spotted Woodpeckers, that were quite
common last winter, and scarce this year, and also the Redpolls that I
mentioned in an earlier mail, that react apparently mainly to the amount of
birch seeds, and that are more numerous than usual this winter.
. Other changes are at an annual scale. Even common birds
numbers may
vary a lot in numbers from year to year. A good example of that is the
Goldcrest, our smallest bird, and unexpectedly the one that keeps most
strictly to insect food also in winter. Severe winters, especially such
with all trees glazed over with ice for longer periods, take a heavy toll
of our Goldcrests, and after such a winter it may take a year or two before
numbers again approach normal. Long-tailed tits are also very nomadic, but
I do not know what governs their movements.
In a few cases such sudden invasions from the inland may lead
to a
temporary nesting population here in the fir plantations nearer the coast.
We have had nesting Red Crossbills here in some years, and after an
enormous influx of Coal Tits some ten years ago, these conifer-loving small
tits nested in Folkeparken for almost five years--now they are gone again.
The Collared Doves that reached Tromsø at the end of their amazing march
across Europe (now being repeated in the US) in the early seventies, have
amazingly enough clung tenaciously to this tiny far north bridgehead ever
since, with the kind help of some ladies in town, who feed the few pairs
throughout the long winter.
But the Jays are an example of changes at a longer time-scale,
and of
those we have had quite a few too. When I first traveled in N.Norway,
during my honeymoon in 1965, we noted everywhere the House Sparrows, Great
Tits, and Pied Flycatchers, as those species then just were penetrating
into the area, helped by increased traffic, more and more feeders around
the houses, and the increased use of nest boxes. When I moved to Tromsø in
1973, the town was still too far north for the Greenfinch, but it took only
few years before we noted the first ones, and now they occur all over
N.Norway; they too profit from feeders, but I suspect that in their case
the maturation of the many fir plantations many places has been an
important factor, both for nesting and for shelter in winter.
Together with the Jay also the Blue Tit is steadily spreading
in our
area; again feeders will have much to say. but also the climate seems to be
changing, with a trend towards milder and still more changeable winters.
That may be one of the reasons, why the Grey Heron is getting steadily more
and more common in our area, and also has started to nest on the island of
Tromsøya (also in a fir plantation, by the way)--these herons stay here
year round, and in winter they must of course get all their food from the
intertidal of the fjords. Another newcomer to the area, although a few may
have been overlooked earlier, is the Red-necked Grebe (Our common nesting
grebe is the Horned (=Slavonian) Grebe). We had seen a few of these grebes
for many years in the open fjords in late winter and spring, and have now
finally also discovered them nesting in inland fresh water---numbers seem
to increase every year, and last week in the Balsfjord record numbers were
counted.
Of course not all bird species increase in numbers. Starlings for ex. we
have clearly far fewer than fifty years ago, and a species as the
Yellowhammer I have not seen on the island in years, while it was regular
in early spring earlier. And locally, on the heavily built-up southern part
of the island of Tromsøya the Willow Grouse, that used to be regular in my
garden, have disappeared, while last spring I also missed the Woodcock that
used to have its display route over my garden, too many dogs and cats, no
doubt!
So even in an area like ours, where the diversity of birds is much lower
than many other places, the picture is never static. Birds come and go!
Wim Vader, Tromsø Museum
9037 Tromsø, Norway
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