01/01/2010
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Pink-footed and bean geese

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Tundra Bean Geese by Steve Young (www.birdsonfilm.com)
Tundra Bean Geese by Steve Young (www.birdsonfilm.com)

Key featured species

  • Pink-footed Goose Anser brachyrhynchus
  • Tundra Bean Goose Anser serrirostris
  • Taiga Bean Goose Anser fabalis
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The problem

Pink-footed and Tundra Bean Geese are similar in both size and appearance. Tundra also has to be separated from the much rarer and more localised Taiga Bean Goose. The three species are closely related – in fact at times they have been treated as a single species (see Birdwatch 129:26-29 for more details of their taxonomy).

pinkfoot.jpgClick here for larger image. Illustration by Ren Hathaway.

The solutions

Pink-footed Goose

Pink-footed Goose is Britain’s most abundant wintering goose, with a population approaching a quarter of a million. The bulk of these occur in Scotland, northern England – particularly Lancashire – and Norfolk. The species is surprisingly rare in Wales and southern England. Large flocks present one of the finest bird spectacles to be seen in this country. Our birds breed in Greenland and Iceland and are here from September to May, with stragglers staying into June.

Being so abundant, Pink-footed Goose must act as the yardstick when identifying the two bean geese. It is a small, compact goose with a short neck and a small, rather triangular bill. On the ground, adults are best identified by their rather dark brown head and neck, which form a marked contrast with their pale bodies with grey-toned upperparts. The most distinctive features are the black bill, which is crossed by a pink subterminalband near the tip, sometimes extending back along the lower edge of the bill, and by their pink legs and feet.

Juveniles show paler heads that contrast much less with their more uniform bodies. They also have plainer, less well-patterned upperparts, the more rounded feathers showing duller buff fringes, and they lack the darker subterminal bars shown by adults. As a consequence, they look duller and more uniform at a distance, and moulting individuals in winter may look rather scruffy.

In flight, Pink-footed Geese again look compact and short-necked, with rather pointed wings. Their contrastingly dark heads and necks usually stand out and they show noticeably pale grey upper-wing coverts. Their most distinctive call is a high-pitched, double-noted ang-ank.

Tundra Bean Goose

Tundra Bean Goose is an erratic winter visitor, usually in small parties. Flocks of more than 10 are unusual. Unlike Pink-footed Goose, it does not have many regular wintering sites, the north Norfolk coast probably being the most reliable area in which to encounter it. Cold winter weather often produces small influxes, usually concentrated in eastern England.

Whereas Pink-footed Goose breeds in Greenland, Iceland and Svalbard (this last population wintering mainly in The Netherlands) it is replaced on the tundra of Russia by Tundra Bean Goose. As the latter has similar ecological and environmental requirements, it is structurally similar to Pink-footed Goose, with a short neck, rounded head and deep, rather triangular bill. It is also similar in size, being only about 2 per cent larger.

Like Pink-footed, Tundra Bean usually shows a discrete subterminal band across the end of the bill, but this is orange rather than pink. Similarly, the legs are also bright orange (duller on juveniles). Although the differences in the bare-part colours are diagnostic, some care needs to be taken, as pink and orange can look surprisingly similar in certain lights or at a distance.

Although Tundra Bean Goose also has a dark brown head and neck, this does not contrast as much with the body, which is browner than that of Pink-footed, with more contrasting pale feather fringing to the darker upperparts. It also has more strongly barred flanks. Adults have rather square upperpart feathers, with brown subterminal bars and neat whitish-buff tips tha tproduce a regular pattern of narrow whitish lines. Like Pink-footed Goose, juveniles have rounded upperpart feathers with less prominent buff feather fringes, they lack the adults’ dark subterminal bars and they show plainer, less barred flanks.

In flight, Tundra Bean lacks Pink-foot’s pale grey forewing, its darker, browner forewing contrasting much less with the rest of the wing, although the primary coverts and bases of the primaries are greyer. Its calls are similar to those of Pink-foot, but slightly deeper.

Taiga Bean Goose

Taiga Bean Goose is now generally regarded as a separate species from Tundra Bean Goose. As its name suggests, it breeds in bogs ,marshes and pools in the taiga forest belt from northern Scandinavia east across Russia. It is very rare in Britain apart from two regular flocks – both of about 200 – that winter on the Slammanan Plateau in Stirlingshire and in the Yare Valley in Norfolk. Unlike Tundra Bean Goose, it is less prone to crossing the North Sea during spells of cold weather, so a trip to the two main wintering sites is the most reliable way of connecting with the species.

Although superficially similar to Tundra Bean Goose, concentrate on size and structure when identifying this species. It is a large goose, similar in size to a Greylag and averaging about 6 per cent larger than Tundra Bean and about 15 per cent heavier. It has a long neck and a longer, less triangular bill that creates a flatter-headed, almost swan-like impression. It also has a long body, which produces a more lumbering gait and more of a side-to-side ‘swagger’ when walking. The important point to remember about Taiga Bean Goose is that many have a bill pattern very similar to that of Tundra Bean Goose, with a discrete subterminal orange band near the tip. However, many others have more extensive orange on the bill, sometimes covering virtually the whole bill, and such individuals are much more distinctive.

As well as having a proportionately longer and shallower-based bill than Tundra, another feature of Taiga Bean’s bill is that it virtually lacks a ‘grinning patch’. On Tundra Bean Goose, the lower mandible bulges, creating a distinct oval gap between the two mandibles. On Taiga Bean the two mandibles fit more closely together so that it lacks this prominent gap.

Whereas Tundra Bean Goose tends to feed in similar environments to Pink- footed Goose – stubble fields, sugar beet fields and so on – Taiga Bean is more likely to be found feeding in longer, coarser vegetation in wetter, marshier environments, where it likes to feed on the roots and seeds of aquatic plants, often burrowing its head into the mud to do so. Also, whereas Tundra Bean Geese tend to associate with Pink-footed or Eurasian White-fronted Geese, Taiga Beans often associate with Greylags.

In flight, Taiga Bean resembles Tundra Bean except that it is heavier-bodied, noticeably longer-necked and has slower wing beats. It has distinctive calls that are deeper and more similar to the honking calls of Greylag Goose, and obviously deeper than those of Tundra Bean. To me they sound like a deep ur-ur.

Moult and sexing

Juveniles of all three species commence their post-juvenile body moult in about October, starting with their head, neck, lower scapular and flank feathers. The moult varies individually, with some birds renewing all their body feathers, at least some tail feathers and some median coverts by late winter, while others retain some juvenile body feathering and most wing coverts into the following summer (Cramp 1977). The moult means that young birds become progressively more difficult to age as the winter advances. When judging the size of these geese, remember that males average about 5 per cent larger than females and that they also average about 10 per cent heavier. This is particularly significant when judging the size of lone bean geese, male Tundra being closer in size to female Taiga.


Refences

  • Cramp, S. 1977. Birds of the Western Palearctic. Vol 1. Oxford University Press, Oxford.