The breeding range of Snow Buntings is circum-polar running through Greenland, Iceland, Northern Europe, Alaska and northern Canada.
Three races are recognised, two of which occur regularly in Europe. These are the Scandinavian/Greenland race Plectrophenax nivalis nivalis and the Icelandic race Plectrophenax nivalis insulae. The Siberian race P.n. vlasowae is a vagrant to western Europe.
Prior to the commencement of ringing studies, it was thought that the majority of Snow Buntings wintering in Britain were from Scandinavia and Greenland. However studies in Scotland revealed that only about 20% of the birds caught were of the Scandinavian/Greenland race, with the majority being of the Icelandic race. Similar studies in The Netherlands have also shown that both races winter there but the ratio of nivalis is usually greater.
This project was begun in 1991 to study the racial composition and sex ratio of Snow Buntings wintering on the north Norfolk coast. We have found that both the Scandinavian/Greenland race and the Icelandic race occur in mixed flocks on the Norfolk coast in winter. They tend to favour certain locations with flocks sometimes numbering several hundred at Snettisham/Heacham, Holkham and Salthouse. The foraging range of these flocks is large and there is often considerable interchange between flocks with small groups and individuals leaving one flock and joining another. Trapping has relied on providing patches of seed, to which the flocks are readily attracted, in areas already frequented by Snow Bunting flocks.
The Project ran from 1991 until 2000 and over 1800 were caught and ringed, and also colour ringed with individually recognisable combinations. This has generated an incredible number of sightings of ringed birds, which has enabled us to build a large database of movements of these individuals both within and between winters. Colour ringing has also produced an incredible number of recoveries, far more than could be expected from metal rings alone.
Birds were marked with a combination of three colours on one leg and with either just a metal (BTO) ring or with the addition of a single colour (which can be above or below metal) on the other. These combinations identify individuals uniquely.
Photo © John Middleton
Snow Buntings ringed in Norfolk have been recovered in:
Snow Buntings originally ringed abroad have come from Belgium (3) and from The Netherlands (1).
The Dutch ringed bird was re-trapped in two consecutive winters at Salthouse and a Belgian ringed bird to which the Group added a colour combination was seen the next winter at Dunkirque, France
Map showing the distribution of Snow Bunting recoveries.
This 1st winter female Snow Bunting that we had colour ringed at Salthouse in Norfolk on 5th December 1997 was seen back in Iceland on 17th March 1998, 1731 km away.
Another remarkable Icelandic race female VN81690 set a British longevity record and you can view those details here
How the race is determined.
The race of females is determined using a feather scoring system which scores the percentage of black on the ninth primary (second innermost), nivalis tending to have a larger proportion of white. Male birds can be raced according to the underlying colour of the rump which is white in Scandinavian/Greenland birds and black in the Icelandic race.
The results indicated that Norfolk is at the southern edge of their range. The flocks consist mainly of females which varies between 81 - 87% of all the birds captured. These are mostly young birds in their first winter (80% of all females), with virtually all the males trapped being in their first winter (90-95% of all males). There tends to be a higher ratio of adults within females. In some years we get almost exclusively the dark Icelandic (insulae) race which follows that of the Scottish pattern, but in others we can get a 50:50 ratio of Icelandic/Scandinavian (nivalis) birds in Norfolk. Nivalis birds tend to arrive later and some have come across the North Sea via Belgium & Holland. We have found this late arrival to be typical of the Scandinavian race. The Icelandic race tends to arrive earlier and also to leave slightly earlier.
The sex ratio of males averaged over the first four years of the study was 16% compared to females and this is one of the lowest recorded anywhere amongst wintering Snow Buntings. Although this is similar to some results obtained in the Netherlands over three years in the seventies which showed an average of 24.3%, and 18.5% in 1989/90. Whereas data for Scotland showed the average percentage to be 35.5%. Work carried out in the first year of our study on flock dominance and hierarchy showed that adult birds were dominant over first winter birds and males over females. It has been suggested that the more dominant birds winter further north with males remaining nearer the breeding areas. Progressing south through the wintering range there are fewer males and also fewer adults and when reaching Norfolk - near the southern extreme of the wintering range - the vast majority of the birds are first winter females.
Whilst the racial composition varies from year to year, in most years the flocks are mainly first-winter Icelandic females. Males show a completely different pattern as the majority, (at least 75%) of males, have been of the Scandinavian/Greenland race. It seems that Icelandic males may not come much further south than Scotland/northern England. Some Scandinavian/Greenland males winter much further south, whether they come through Scotland or across the North Sea is unclear. Recoveries of nivalis males in spring, controlled on migration tend to suggest that they may follow the east coast to Scotland. Whether they turn west to Greenland or east to Scandinavia is not known. It has been suggested that nivalis wintering in the Netherlands come from Greenland and it has been shown that birds from both breeding areas are found in Britain, but at present we cannot state the breeding origin of nivalis birds found wintering in Norfolk.
We have already mentioned some aspects of flock dominance and hierarchy and these studies utilised the colour-ringing project to obtain results. Amounts of seed provided at the sites used to capture Snow Buntings were manipulated to see how the flock reacted to such changes. How aggression and interaction between individuals varies with changes in food availability were observed using visual aids such as telescopes or recorded using video cameras. These results were published by Paul Dolman in Oecologia (1995) Volume 102, Number 4. Pages 511 -514. The intensity of interference varies with resource density: evidence fom a field study with snow buntings, https://link.springer.com/article/10.1007/BF00341364