BACKGROUND
East Canadian High Arctic Light-bellied Brent Geese (Branta bernicla hrota) are amongst Ireland's most important waterbird species. Breeding in the archipelago of the eastern Queen Elizabeth Islands, well north of the arctic circle in Canada's extreme north-east (Nunavut), this population spend the winter primarily at sites located around the Irish coastline but as far south as northern Spain and northern France. On both spring and autumn migrations they traverse the enormous Greenland ice-cap and spend some weeks staging in the bays and fjords of western Iceland. Irish wetlands hold almost over 90% of the entire flyway population and are exceedingly important between October and March of each year.During April and May and again primarily in September/October the population is concentrated in the fjords of western Iceland. On both spring and autumn migrations the abundant food resources in Faxafloi and Breidafjordur are extremely important to the population, providing the most abundant food resources the birds have access to before the birds cross the arctic circle for the summer. It is likely that many of the resources acquired in spring staging areas are used for 'capital' investment in breeding. At this time of year the birds are feeding for a great deal of the day (it never fully gets dark in May) on intertidal Zostera, green algae (Enteromorpha and Ulva), saltmarsh grasses and terrestrial species on agricultural and amenity grasslands.
POPULATION STATUS AND DISTRIBUTION
The flyway map shows the broad migratory route and general areas of importance to this and other North American Brent populations. Brent have a circumpolar breeding distribution and all populations winter in sub-arctic to temperate areas in N America or Europe. The 'Irish' population is one of four recognised flyway populations of Branta bernicla hrota and six populations of Branta bernicla bernicla. These are mostly separated by a combination of their geographical flyway and plumage characteristics (particularly belly colours - see pictures below). More detail on these population is given in key references Robinson et al. 2004 and Reed et al. (1998).
Three of these N American Brant flyway populations are distinguishable by plumage as illustrated in the pictures below - Atlantic and Irish (Eastern High Arctic) are inseperable, but the more westerly breeding species get progressively darker - Western High Arctic (Grey-bellied) Brent breeding in the central Queen Elizabeth Islands being intermediate between Eastern High Arctic and the very dark Black Brant nigricans.
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WESTERN HIGH ARCTIC
Around 35 sites around the Irish coast are used from November through to March/April {Map X}. Surveys of the Icelandic west coast have also established the importance of key sites there {Map 1}. The situation in Greenland and Arctic Canada is much more poorly known, however. Historically the population has undergone fluctuations from lows in the 1960s of 10,000 to the recent peaks approaching 40,000 birds {GRAPH}. Similar to many other arctic-nesting species there are considerable between-year differences in productivity.
THE BRENT GOOSE YEAR
There are few times in the year when all Brent are in one country; at most times the first birds to migrate have moved to our beyond the main destination and there are stragglers. It is fair to say however that between October and April the majority of Brent are in Ireland, in May in Iceland, between June and August in Canada, and in September in Iceland. This section describes the annual cycle.WINTERING
Between October and March, most birds are in Ireland and the other parts of the wintering range (western parts of Scotland, Wales and England in small numbers, Jersey and northern France). In October some birds typically remain in Iceland and some birds - probably the earliest migrants are as far south as France. As numbers decrease in Iceland so they increase to peaks of around 4,000 at Lough Foyle and 25,000 at Strangford Lough, decreasing at these sites through November as the wave of birds moves farther south, splitting into smaller numbers and flocks occupy many coastal sites in Ireland and beyond.Birds are strictly distributed around the coast, feeding on inter-tidal habitats for the first part of the year and making increasing use of grasslands and saltmarsh habitats as the season progresses. From December onwards flocks at many sites are increasingly using grassland habitats and there they form especially dense flocks.
SPRING MIGRATION
In late March the first birds will have arrived in Iceland, numbers peaking there in mid-May. In the latter half of that month the vast majority of birds will be in western Iceland fattening in preparation for the onward migration to the breeding grounds. In late May the entire population head west destined for Greenland, the ice-cap crossing and crossing the Davis Strait and Baffin Bay. Only small numbers remain in Iceland and these birds are probably unfit to migrate to Canada.
The sites used in western Iceland are similar in spring and autumn, extending from the Reykjanes peninsula in the south-west to the north Snaefellsness peninsula. Aside from small numbers on the south coast on passage, all staging Brent use west coast sites. These are the most typically estuarine bays in Iceland and of course are the closest to the Canada-Greenland-Ireland migratory route.
The sites marked 1-16 are all important and vary considerably, ranging from the accessible sites around Reykjavik (Sites 1-3) where birds feed on golf courses, the Presidential grounds and in close proximity to the public, to the wild and inaccessible flocks at Myrar/Straumfjordur in Faxafloi and Alftafjordur in Breidafjordur.
This stage of the annual cycle is especially interesting and consequently are fair amount of research work has been undertaken, especially in spring. Further details are available on the Staging Ecology page.
BREEDING SEASON
The first arrivals in the Queen Elizabeth Islands are in early June and at this stage our knowledge of how and when the birds move around remains poor (though our satellite telemetry studies have shed some light). Given the time limitations to breeding before having to depart south in August, we suspect that breeding birds search out suitable nesting areas quickly and initiate nesting by mid-June. After laying and incubation over a period of around 25 days eggs hatch and birds move to brood-rearing locations. 40 or so days later the adults have undergone their annual moult (rendering them flightless) and young have fledged.
Information from this time of year is notably limited but recent work in 2005 (Bathurst and Devon Island) and especially in summer 2007 (Ellesmere, Axel Heiberg and Bathurst Islands) has added to our knowledge. Further details are on the Breeding Biology page.
AUTUMN MIGRATION
The first departures from the breeding range are likely to occur from mid-August onwards, kicking-off in earnest at the end of the month and probably peaking in early September. Peaks numbers in Iceland occur in mid-September and from then onwards (when late-arriving birds may still be in Greenland) the largest proportion of the population gravitates southward. There is some evidence that some birds may even bypass Iceland on the southern migration (we think those birds which are seen in Ireland in late August/early September might be doing this). By mid to late October most birds have left Iceland for areas to the south and the presice timing of main southerly movements is probably largely determined by weather conditions (birds awaiting favourable conditions for migration).
