Barnacle Geese - answer .........................................................Chas Holt

Chas Holt Barnacle Geese at Landguard – a contribution from WeBS to the question of ‘what’s going on?’

As described in Nigel Odin’s article, the UK hosts three relatively discrete populations of Barnacle Goose: two migratory populations that breed in Greenland and Svalbard, respectively, and a third naturalised population that is steadily spreading across lowland Britain. The Greenland population winters almost exclusively in Ireland and western Scotland (where the peak on Islay can reach over 50,000 birds), while the Svalbard population winters primarily on the Solway Estuary (c.30,000 birds) with a smaller number at Lindisfarne and Loch of Strathbeg. Both the migratory populations and the naturalised population have increased in recent decades (see Fig. 1). A quick search of the new online WeBS report (Austin et al. 2014), now searchable by county, reveals that the number of Barnacle Geese recorded during WeBS counts in Suffolk has increased in recent years. This concurs with Nigel’s summary of counts as sourced from Landguard Bird Observatory’s records. Favoured WeBS sites in Suffolk are Minsmere, North Warren, Benacre and Lound Waterworks. The suggestion that the east coast of England may receive birds from the growing Dutch population seems reasonable, and this would also help to explain the increasing numbers that have been observed in some other areas, particularly the Humber Estuary where annual maxima tend to peak in autumn or early winter. In the most recent WeBS report, covering 2011/12, the highest count of naturalised Barnacle Geese in the UK was 812 on the Humber Estuary in October (for additional evidence supporting this estimate, see STOP PRESS below). To summarise, it is therefore likely that birds seen passing Landguard may represent a combination of birds from the Netherlands, with movements of a more ‘local’ population that tends to be centred on the Minsmere area.

Fig. 1 - Population trends for bio-geographic populations of Barnacle Goose in the UK, 1966/67 to 2011/12 (Greenland population censused annually since 1988/89).

WeBS report Austin, G.E., Read, W.J., Calbrade, N.A., Mellan, H.J., Musgrove, A.J., Skellorn, W., Hearn, R.D., Stroud, D.A., Wotton, S.R. & Holt, C.A. 2014. Waterbirds in the UK 2011/12: The Wetland Bird Survey. BTO/RSPB/ JNCC, Thetford. http://blx1.bto.org/webs-reporting/

STOP PRESS In a recent British Birds article it was stated that Musgrove et al (2013) derived their breeding estimate for the naturalised population from the number of apparently naturalised birds counted in the winter. RBBP (Holling et al 2014) data records a minimum of 164 pairs but, as breeding pairs are poorly recorded, considered that an estimate of around 1000 breeding pairs was not unrealistic.

Holling, M. & the Rare Breeding Birds Panel (RBBP) 2014 ‘Non-native Breeding Birds in the UK, 2009-11’ British Birds 107: 130-131.