Greater white-fronted goose in CaliforniaGreater white-fronted geese,Texel, Netherlands (2013)
Thegreater white-fronted goose (Anser albifrons) is aspecies ofgoose, closely related to the smallerlesser white-fronted goose (A. erythropus).[2] The greater white-fronted goose ismigratory, breeding in northernCanada,Alaska,Greenland and Russia, and winters farther south in North America, Europe and Asia.[1] It is named for the patch of white feathers bordering the base of its bill:albifrons comes from the Latinalbus "white" andfrons "forehead".[3] In the United Kingdom and Ireland, it has been known as thewhite-fronted goose; in North America it is known as the greater white-fronted goose (or "greater whitefront"), and this name is also increasingly adopted internationally.[1] Even more distinctive are the salt-and-pepper markings on the breast of adult birds, which is why the goose is colloquially called the "specklebelly" in North America.
Greater white-fronted geese are 64–81 cm (25–32 in) in length, have a 130–165 cm (51–65 in) wingspan, and weigh 1.93–3.31 kg (4 lb 4 oz – 7 lb 5 oz).[4][5] They have bright orange legs and mouse-coloured upper wing-coverts. They are smaller thangreylag geese. As well as being larger than the lesser white-fronted goose, the greater white-fronted goose lacks the yellow eye-ring of that species, and the white facial blaze does not extend upwards so far as in the lesser.[6]
The male is typical larger in size, both sexes are similar in appearance—greyish brown birds with light grey breasts dappled with dark brown to black blotches and bars. Both males and females also have a pinkish bill and orange legs and feet.[7]
Greater white-fronted geese make a variation of sounds, but notably the most recognizable is the high pitched cackle that can be imitated by the sounds "he-he." There is a distinct breaking of the note from the first cackle to the second.
The appearance of European or Russian white-fronted geese, of thesubspeciesalbifrons and Greenland white-fronted geese, of the subspeciesflavirostris (which winters in the British Isles and occasionally reaches the northwest European mainland), differ in a number of ways. The Greenland white-fronted goose, in all plumages, looks darker and more "oily-looking" than the European and Asian white-fronted goose, both at rest and in flight.[8]
The following are the differences which apply to first-winter plumage:[8][9]
The mantle and scapulars offlavirostris have narrow, indistinct pale fringes creating a uniform appearance to the birds' upperparts, whereasalbifrons has noticeable whitish fringes creating obviously barred upperparts
The tertials offlavirostris have indistinct pale fringes, whereas these pale fringes are more noticeable onalbifrons
The lesser- and median-upperwing-coverts offlavirostris have narrow, indistinct pale fringes, creating a rather uniform appearance to the wing, whereas onalbifrons, these fringes are prominent and broad, creating wing-bars
The greater-coverts offlavirostris are dark grey, with a narrow white tip, forming a narrow wing-bar; onalbifrons they are blue-grey, with prominent white tips, forming a bold wing-bar
The flank-line is narrows and white onflavirostris, but broad and bright white onalbifrons
The tail offlavirostris is dark brown, with a very narrow white tip and sides; that ofalbifrons is dark grey, and the white tip and sides are at least double the width of the corresponding areas onflavirostris
The bill offlavirostris is orange-yellow with a dark nail, compared with the bright pink bill ofalbifrons which has only a hint of dark on the nail; in addition the bill offlavirostris is longer and appears slimmer than that ofalbifrons
The belly-barring on adult birds is on average more extensive onflavirostris than onalbifrons, but the individual variation in both forms renders this of limited use as an identification feature.[8]
The bill of adult Greenland white-fronts are also orange-yellow at the base, but can be more pinkish-yellow on the outer-half, thus close in colour to European white-fronts; the colour difference is more easily determined in dull, flat light rather than bright sunshine.[8]
The Greenland white-fronts are of conservation concern. While most populations of the species have been increasing, the Greenland population continuously declined in the first two decades of the 2000s (after having continuously increased in the two preceding decades). The reason for this decline is not entirely clear, but likely related to more extreme weather conditions.[10]
The greater white-fronted goose is divided into fivesubspecies. The nominate subspecies, the European white-fronted goose (A. a. albifrons) breeds in the far north of Russia and winters further south and west in Europe and Asia.
Three other restricted-range subspecies occur in northern North America: Gambel's white-fronted goose (A. a. gambeli) in interior northwestern Canada and wintering on the coast of the Gulf of Mexico, slightly larger than the nominate form, the Pacific white-fronted goose (A. a. frontalis) and the tule goose (A. a. elgasi) in southwestAlaska, largest and longest-billed of all, both wintering inCalifornia. All these subspecies are similar in plumage, differing only in size.[11]
The very distinct Greenland white-fronted goose (A. a. flavirostris) breeding in western Greenland, is much darker overall, with only a very narrow white tip to the tail (broader on the other subspecies), more black barring on its belly and usually has an orange (not pink) bill. It winters inIreland and westernScotland.
Birds breeding in the far east ofSiberia east to Arctic Canada, wintering in the United States and Japan, have been described asA. a. frontalis on the basis of their slightly larger size and a marginally longer bill. Another putative East Asian subspecies (A. a. albicans) has also been described. A 2012 study has found thatfrontalis andalbicans do not merit subspecies status, the former being synonymised withgambeli and the latter with the nominate subspecies; this study found that these forms had been named on the wintering grounds from specimens whose breeding grounds were unknown.[12]
Ecological studies conducted in 2002 suggest the Greenland birds should probably be considered a separate species fromA. albifrons.[13] Of particular interest is its unusually long period of parental care and association, which may last several years and can include grandparenting, possibly unique among theAnseriformes.
The North American midcontinent birds of the subspeciesA. a. gambeli – which in 2010 had a fall population of about 710,000 birds – breeds from theAlaska North Slope across the western and central Canadian Arctic.[citation needed] The Pacific white-fronted goose of the American Pacific coast, which in 2010 numbered approximately 650,000 birds,[citation needed] and the tule geese, which are estimated to number 10,000 birds, nest in western Alaska. The midcontinent geese gather in early fall on the prairies of westernSaskatchewan and easternAlberta, spending several weeks feeding before heading to wintering areas near the Gulf of Mexico, into northern Mexico.[7] The Pacific birds migrate south down the Pacific coast, staging primarily in theKlamath Basin of southern Oregon and northern California and wintering, eventually, in California'sCentral Valley.[7] The tule goose is somewhat rare and has been since the latter half of the 19th century,[14] presumably it was affected by destruction of its wintering habitat due to human settlement.[11]
In theBritish Isles, two subspecies overwinter: Greenland birds in Scotland and Ireland, and Russian birds in England andWales. They gather on farmland at favoured traditional sites, with a famous flock gathering atWWT Slimbridge,Gloucestershire, England.[15] Greenland birds also overwinter in Ireland and from late September and through the winter months, Ireland is home to almost 50% of the Greenland population of white-fronted geese.[16]
A. a. albifrons andA. a. flavirostis are among thetaxa to which theAgreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.
Weather conditions are a key factor in the annual breeding success of white-fronted geese. In the Arctic, the window of opportunity for nesting, incubating eggs, and raising a brood to flight state is open briefly, for about three months. Arriving in late May or early June, white-fronted geese begin departing for fall staging areas in early September. This means that a delayed snowmelt or late spring storm can significantly reduce the birds' reproductive success.[7]
Midcontinental white-fronted geese in North America have many breeding areas and each group in each breeding area differs in its migration time and wintering location. There are six breeding areas, including interior Alaska, the North Slope of Alaska, westernNorthwest Territories, westernNunavut, central Nunavut, and eastern Nunavut. These spatial differences lead to different departure times for white-fronted geese leaving their breeding areas. Birds from interior Alaska start migrating earlier during autumn and fly farther south to winter.[17] Due to their migration, white-fronted geese are commonly sought after by waterfowl hunters, all across the country.
A technique using stable isotope analysis from a white-fronted goose has shown promise in providing a way to determine the migratory route birds take from their wintering to breeding grounds.[18]
^Banks, R.C. (2011). "Taxonomy of Greater White-fronted Geese (Aves: Anatidae)".Proceedings of the Biological Society of Washington.124 (3):226–233.doi:10.2988/11-14.1.S2CID85077293.
^Fox, A.D.; Stroud, D.A. (2002). "Greenland White-fronted Goose".Birds of the Western Palearctic Update.4 (2):65–88.
^Horacek, Micha (2011). "Backtracking the movements of a migratory bird: a case study of a white-fronted goose (Anser albifrons)".Rapid Communications in Mass Spectrometry.25 (20):3146–3150.Bibcode:2011RCMS...25.3146H.doi:10.1002/rcm.5209.PMID21953970.
.jpg)
_(cropped).jpg)
