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Kanadagås av ukjent underart ved Østensjøvannet i Oslo Unidentified Canada Goose (B. canadensis ssp) at Østensjøvannet in Oslo, Norway  Den 3. februar oppdaget Jørn R. Gustad og Eirik Grønningsæter en avvikende kanadagås (fuglen til venstre) ved Østensjøvannet. Ut fra de karakterer den viser peker det dog i retning av underarten parvipes. The bird was obvious in pair with another Canada Goose (shown below), probably Branta canadensis canadensis, shown by close social contact in all situations, both by rest and in activity. The mate was believed to be the male, because it was chased by another bird/pair. The mate was not a big bird/male, and the suspected parvipes was a bit smaller than this.  The suspected parvipes (above) was immediate discovered by its buff breast, in great contrast to the surrounding birds. At closer inspection several noticeable details in head was noted; square-looking head, short and neat bill and tiny and "tilted" chin patch (shown in the illustration below). The neck of the bird was looking thick compared to the surrounding canadensis's, and also shorter may to this.  The bird was (may also to this looking) very eased, and was just stretching its neck when drinking. Even then the neck looked short and relatively thick. The bird has not a gular line (shown in the right picture below) like in taverneri, but a bib into the white of throat from the side of the bill was present. I think this is a character that even canadensis can show, but have not found prove on this. The upper side of mantle/wings was darker, maybe created by the broader lighter fringes to the feathers on the mate and/or longer spacing between this fringes lines on the back on the possible parvipes.  The bird is a suspected parvipes due to its large size (pro interior/parvipes), its buff breast (pro parvipes/taverneri/hutchinsii), its square-looking head (pro parvipes/taverneri/smaller ones), its bill size/shape (pro parvipes/taverneri?), its chin spot (pro interior/parvipes/taverneri), its neck shape (pro parvipes/taverneri) and its throat (pro interior/parvipes/taverneri?). The observation was made in comfortable weather, in good light at distance of 2-20 meters. Birds giving the same impression as the above presumed parvipes are depicted in Bird World vol 14: no 2 page 60 plate 10 and page 58 plates 4 and 5 (perfect chin patch), and no 12 page 517 plate 15 (all above characters but the character in throat is not properly seen). Text by Jørn R. Gustad.  Vi ønsker gjerne kommentarer vedrørende underartstilhørighet. Responder her hvis du har noen synspunkter. Evt kommentarer blir lagt ut løpende./If you have any comments about ssp, pls respond here. Kommentarer ... ... fra Søren Ulrich Thomsen, Danmark, 15. mars Jeg har en kommentar til artiklen om "Kanadagås af ukendt underart ved Østensjøvannet i Oslo". Jeg har kigget i en bog der heder "photograhic Handbook of the Wildfowl of the Wold". Her er der foto af alle 11 kanadagåse racer. Branta canadensis interior er det ikke, det er den af alle racer, der har mest hvidt i hovedet. Om det er en hybrid mellem grågås og kanadagås, de 4 jeg har set i Danmark, havde alle næsten helt hvid hoved. Mit bedste bud ud fra de foto der er i den bog er "Branta canadensis Parvipes". I 1999 så jeg en af de små racer af canadagås, i det danske vadehav, sammen med 3000 bramgæs som den ligner meget.
This is a short reply to Mr Grønningsæter just to tell that he has forgotten to read the whole text, when it de facto reads why the bird is suspected to be a parvipes... I am sure on that the birds are a pair, not a parent and
young. Familiary bounds are strong in breeding season (June-September), and are gradually
loosed up late in the year (September-October). Based upon experiences with Oslo birds
there are not observed strong familiary bounds between geese in mid winter. There are
sometimes family groups, e g seen by a hybridizing pair of Greylag and Canada Goose, and
their youngs. When you catch on of the youngs in winter in such family groups, you never
get the same reaction of the parents as you do in the breeding season. When releasing the
possible parvipes (a female), the male came honking in flight to it, and they had a
reunion consert. Quite cute and definately a seremony for a couple with sexual
relationship! ... fra Eirik Grønningsæter, 20. februar In the summary that Mr.Gustad gives at the end of his description of the bird, he has forgotten to mention the reason why we think this is a probably parvipes (Lesser Canada goose) and not an interior. The size of the bird makes it canadensis, parvipes or interior. But the length of the neck is in our opinion too short for both interior and canadensis. And pluss all the other features described on this bird, this sums up to a most likely parvipes. Some have commented that the bill is too short for a parvipes. But after a successful catch with some bread and impressing gymnastics, we took some meassurements. Bill with head: 124.2mm and Upper bill length: 51.6mm. Sex: Female As far as these meassurements shows, the bill of this bird is not at all too short for a parvipes. (I'm sorry not to remember my references at the moment). There has also been some discussion wether or not this is an adult bird or if the strong connection between the two birds is just because it is a mother (the more normal of the birds), and her young (the possible parvipes). Geese are known to show a strong family relationship even after their first winter, so deciding that this is a adult pair just because of their behaviour is a bit tricky if you ask me. The fringes of the coverts on the back are in my opinion not as pale as they should be for an adult. (But then again, I have noe excperience with other subspecies than canadensis. But even so, I think this bird is a 1. winter individual. If I'm right in my aging of this bird, it makes the parvipes theory a bit more unlikely. When said that, the partner (or parent) is a rather small canadagoose compared to most other canadensises, though some of them are as small as our partner/parent bird. Except for the relatively small size, the parent/partner show in my opinion no other signs that suggests anything other than canadensis. Copyright Andreas Gullberg © 2002 |
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