BLAGDON LAKE BIRDS

Canada Goose



Canada Goose Branta canadensis (Linnaeus, 1758)

Canada Goose Branta canadensis canadensis (Linnaeus, 1758)

(Common IR. B.)

Canada Goose Branta canadensis, Holt Bay © Nigel Milbourne, 2012

There are several recognised races of Canada Goose Branta canadensis and the taxonomy of the group is far from clear, though there is quite a lot of work being done to bring some clarity. Currently, the general consensus is that the group should be divided into 12 sub-species that are in turn divided into large and small race groups which have been named Canada Goose Branta canadensis and Cackling Goose Branta hutchinsii by the American Ornithologists Union (and subsequently followed by the BOU). The Greater Canada Goose group comprises seven races: Atlantic B. c. canadensis, Interior B. c. interior, Giant B. c. maxima, Moffit's B. c. moffitti, part of the 'lesser complex' B. c. parvipes,Vancouver B. c. fulva and Dusky B. c. occidentalis.

We know that genuine wild birds visit these shores, especially the more easily recognised smaller forms, and thanks to modern optical equipment and better field guides these are becoming easier to pick out. However, Cackling Goose has yet to be accepted onto the British List. A ♂ individual bearing neck-collar 6TU2 from Maryland, USA, provided the first confirmed evidence of transatlantic vagrancy for Canada Goose in Nov. 1992 as reported in the BOURC 39th Report (October 2010). The BOU has accepted Canada Goose onto the British List in categories A, C2 and E* as a result (vagrant, probably sub-species B. c. interior, and naturalised breeder B. c. canadensis).

Canada Geese were introduced into Britain over 300 years ago (Atkinson-Willes, 1963) with various authors commenting that they were present in London in the 1670's among the Kings Wildfowl in St. James's Park (e.g. Owen, 1977). It is suggested in BWP that birds introduced into Britain were, in the main, probably Atlantic Canada Goose (the nominate race) but some Giant Canada Geese may originally have been involved as well. Kear et al (2004) state the introduced sub-species is unclear and was possibly Interior Canada Goose and Giant Canada Goose. Later they were released on many large estates but these, more or less, remained sedentary and it wasn't until the middle of the last century that the Canada Goose was considered to be a feral species in Britain (Palmer 2000). British breeding birds undertake limited local movement subject to food availability and disturbance, though pairs spread out to breed. Most authors also make mention of moult migration and cite those, which since c. 1950, move from Yorkshire to the Beauly Firth in Scotland to moult. So it is interesting to note, therefore, that one found dead at Blagdon on 15th August 1988 had been ringed 690km away, on the Beauly Firth, Scotland on 7th July 1984.

Locally, it is reported that Canada Geese bred at East Clevedon in the 1860's and Wells Palace Moat in 1901 (Palmer & Ballance, 1968). In 1918, Donald Carr wrote "Five visited the lake on September 16th, three appeared to be birds of the year". Until I discovered Carr's record, the earliest record for Canada Goose at Blagdon was previously said to be of 9 seen at the water's edge at the south end in 1935 and, as this species was not admitted to the British list at the time, the record was annotated as "probably of 'escaped' birds". It was many years before the next record in 1962 which was commented on thus: "Single bird at water's edge, BL. Records Jan-Mar 1962, from widely separated localities evidently refer to wild birds (Wildfowl Trust, Slimbridge, reports there was no movement from the stock at Frampton-on-Severn, Glos.)." Indeed, subsequent evidence suggests that British birds had, on occasion, moved south to France during spells of cold weather. The next occurrence at Blagdon was in April 1969.

After a few sightings in the 1970s, the number of records really began to take-off in the mid-eighties. Canada Geese successfully bred at the lake for the first time in 1982 (four young reduced to two) but the absence of an island offering a safe nest site means this is an unusual event.

Looking at the monthly maxima (see below) it is evident that a flock starts to build in November and over-winters before departure in February. At the time of writing this flock numbers between 2-300 individuals. What is more puzzling, however, is the apparent autumn peak in September in some years for which I have no ready explanation at present. If one were to rely solely on the WeBS counts, then this fluctuation in numbers might be put down to disturbance or some other factors (e.g. farmers actively discouraging grazing on their pastures by using bird scarers). It is very noticeable that goose numbers vary from hour-to-hour as they move between lakes and farmland. In order to counteract this variation I have made regular counts each month in an effort to give a truer picture than the once a month, mid-morning, WeBS count that often takes place when many of the geese have left the lake. So, I suspect the peak may be real and an explanation needs to be sought.

Canada Goose Monthly Maxima

Canada Goose monthly maxima at Blagdon Lake 1994-2003

Like other geese, Canadas undergo a complete post-breeding moult and the wing feathers are replaced simultaneously over a period of 3-4 weeks during summer, with the precise timing said to be markedly dependent on latitude and climate (Cramp & Simmons, 1978). There is evidence of a flock of up to 200 birds coming to the lake to affect their post-breeding moult in June and July.  This is a relatively new phenomenon beginning in the last fifteen to twenty years (see below). Numbers built quickly in the late eighties but seem to have stabilised during the last decade. The timing of the influx accords with the known flightless period during the first week of July when the 'annual goose round-up' traditionally takes place at Chew Valley Lake. Careful notes made during 2003 suggest that the geese arrive at the local reservoirs at the end of May and by the middle of June they have decided at which lake they are going to moult. The flightless period lasts from the middle of June to the middle of July and a count made during the first week of July (or a week either side) would be a more accurate way of determining the moult flock size than averaging maximum counts made during June and July.

As Canada Geese usually feed out of the water on grass, the level of the lake seems to have little bearing on the numbers present. When flightless, it is said that they need to have access to short-cropped grass that they can walk to from the water, as they tend to shun higher vegetation where they would be at increased risk from concealed predators. The summer moult flock in years of high water levels, therefore, moves around the lake seeking areas where they can evade disturbance to graze because they don't have flight access to nearby farmland. However, when the water level drops sufficiently to allow access to the abundant weed growth that occurs at the lake, the geese spend much of their time feeding in the water during the flightless period - only coming ashore to preen and rest for short periods.

Size of Canada Goose Moult Flock

Size of Canada Goose Moult Flock

The Chew Valley Ringing Station kindly provided me access to their Canada Goose database. There are over 300 records involving birds ringed, controlled or recovered at Chew Valley and Blagdon Lakes. There was some Canada Goose ringing at Blagdon in the late 1980s and the information from this is too limited to draw any meaningful conclusions. However, analysis of the whole dataset shows that the majority of records concern birds that fly to and from the Bristol Reservoirs and Somerset / Devon. There is also evidence of a smaller movement to and from Dorset. If we consider the conventional wisdom that Canada Geese in Britain fly north to moult in summer then the movement to and from counties south of Bristol becomes logical. During recent years I have looked for ringing controls throughout the year and it is quite noticeable that birds in the moult flock do not seem to have been ringed. I feel that there are discreet occurrences of geese as follows (i) summer moult flock from southern counties e.g. Dorset and Devon, (ii) resident local flock that moves between CVL and BL, and (iii) migratory birds that stop-over during autumn when feeding conditions are good. The Avon Bird Report reported that the then Ministry of Agriculture Fisheries & Food granted a licence for shooting on nearby farmland in 1998 but I don't know the outcome at present.

The geese feed frequently on Holt Farm fields along the south shore in the winter.  When in moult, the birds move around the lake to find undisturbed areas in order to rest and preen on the bank.

Bibliography (sources of information)

  1. Atkinson-Willes G.L. (ed.). 1963. Wildfowl in Great Britain. London.
  2. Blathwayt, Rev. F.L. (ed.). Report on Somerset Birds, 1935. Somersetshire Archaeol. & Nat. Hist. Soc.
  3. British Ornithologists' Union. British Ornithologists' Union Records Committee 39th Report (October 2010). Ibis 153: 227-232, Jan. 2011.
  4. Chadwick, P.J. (ed.). Avon Bird Report, 1982. Avon Ornithological Group.
  5. Cramp S. & Simmons K.E.L. (eds.) 1978. Handbook of the Birds of Europe, the Middle East and North Africa. The Birds of the Western Palearctic. Volume I. Oxford.
  6. Davis, H.H. (ed.). Somerset Birds 1962. Somerset Ornithological Society.
  7. Davis, H.H. (ed.). Bristol Bird Report 1962. Bristol Naturalists' Society.
  8. Davis, H.H. (ed.). Somerset Birds 1969. Somerset Ornithological Society.
  9. Kear, J. (ed). 2005. Bird Families of the World. Ducks, Geese and Swans. Vol. 1. Oxford University Press.
  10. Owen M. 1977. Wildfowl of Europe. London.
  11. Palmer E.M. & Ballance D.K. 1968. The Birds of Somerset. London.
  12. Palmer P. 2000. First for Britain and Ireland 1600-1999. Chelmsford.

Updated 2 January, 2014