Náttúrufræðingurinn - 1984, Side 98

tween Ross’ Geese and Lesser Snow
Geese. - Auk 88: 856-875.
Voous, K. 1973. List of recent Holarctic
bird species. Non-passerines. — Ibis
115: 612-638.
Ævar Petersen. 1970. Fuglalíf í Skógum á
óshólmasvæði Héraðsvatna í Skaga-
firði. — Náttúrufræðingurinn 40: 26—
46.
SUMMARY
A pair of white geese (Anser
caerulescenslrossii) nesting in
North Iceland.*
by
Ævar Petersen
lcelandic Museum of Natural History
Laugavegur 105
P.O. Box 5320
125 Reykjavík
In the summer of 1963 a pair of white
geese was discovered nesting in
Skagafjörður, N-Iceland (Fig. 1). They
were at first believed to be Lesser Snow
Geese (Anser caerulescens), which at that
time were only known as rare vagrants in
Iceland, let alone breeders. Later the idea
developed that the geese were Ross’ Geese
(Anser rossii).
This first nesting attempt was termin-
ated by the sudden swelling of the river
Héraðsvötn, flooding the nesting locality
named Skógar (Fig. 2), a delta area rich in
bird life (Ævar Petersen 1970).
The pair returned in summer 1964. The
last report of the birds that summer (from
June 12th), states the pair incubating 5
fertile eggs. The final breeding result is
* Rare and vagrant birds in Iceland. Report
2: Icelandic Museum of Natural History.
therefore unknown. This summer the pair
was photographed at nest (Figs 3, 4, 5, and
7).
The third consecutive year, 1965, only
one of the geese was seen, and again in
1966. The mate was found dead in summer
1965, probably shot by a hunter.
From the beginning there were doubts
about the identity of the geese at Skógar.
They were considered most likely to be
Ross’ Geese, but this was not certain (Finn-
ur Guðmundsson, unpubl. diary). Cer-
tainly the pair’s eggs pointed to that spe-
cies, those secured measuring 76.30 x
45.25 mm, 69.45 x 45.80, and 71.20 x
47.60 mm (cf. Ryder 1971). The eggs are
now in the Icelandic Museum of Natural
History, Reykjavík.
In 1979, upon seeing for the first time,
the photographs published here, I realized
the geese could not be Ross’ Geese.
Neither did they tally with Lesser Snow. I
therefore consulted Dr. J. Ryder, Canada,
who further asked the opinion of two col-
leagues, Drs A. Dzubin and D. Trauger,
the three of them having published a joint
paper on Lesser Snow x Ross’ hybrids
(Trauger, Dzubin and Ryder 1971). Their
verdict was unanimous with my opinion
that the birds were hybrids of the two
above species, possibly F2 or F3 back-
crosses.
A clue to the origin of these geese, was
provided when sightings were made in
Scotland of white geese in the same years
as when the pair nested in Iceland. The
specific identity of the Scottish birds was
much debated, most likely because they
were hybrids (cf. Macmillan et al. 1963,
Crawford et al. 1963, Macmillan 1964). A
pair of ringed white geese was seen in
successive winters in Scotland during this
period. This pair was believed to be the
same as that nesting in Iceland (Macmillan
1964, Ogilvie 1978). Althougth not fully
proven this is refuted. The circumstantial
evidence for this, includes: (1) Finnur
Guðmundsson (unpubl. diary) described
the Skógar pair as being of very unequal
size. This contrasts with that of the Scott-
ish pair (Macmillan et al. 1963, Crawford
188