Spring stopover routines in Russian Barnacle Geese Branta leucopsis tracked by resightings and geolocation

By attaching 9-g loggers (recording dusk and dawn times to a memory chip) to the coded leg rings of Barnacle Geese Branta leucopsis caught in a breeding colony at Tobseda (68°35'N, 52°20'E) on the arctic coast of the Russian Federation in 2003 and by their recapture and retrieval in the 2004 season, we reconstructed the year-round movements of 19 females. We analysed spring migration movements of logged birds until they entered the zone of continuous daylight (c. 20 May), supplemented by ring reading in the colony. The technique also enabled description of incubation rhythm in these arctic breeders, allowing inferences about attempt and timing of breeding without the necessity of direct observation. Although the birds did not necessarily travel together, most travelled on 14–15 (9 individuals) and 17–18 May (10 birds) when favourable conditions for long-distance flights prevailed. The majority of birds remained in the Wadden Sea well into May, and only 6 staged more than a week anywhere in the Baltic (median staging period 4 days). The majority reached the White Sea by mid-May (latest 23 May) after which near-continuous light precluded further locations. Most tracked individuals spotted in the colony arrived during 6–11 June (mean 8), on average 4 days before first egg date. The median laying date for 17 ‘logger’ birds (from direct observation or backdating from start of incubation) was 13 June (range 5–19), the same as for the colony as a whole in 2004 (n = 385). We conclude that most Tobseda birds tend to overfly the Baltic, and eastern White Sea staging areas are used for on average three weeks before arrival at the breeding colony. Judging from the timing in 2004, rapid follicular development must commence at pre-colony staging sites, and from observations in 2002 we suspect these to be on the Kanin Peninsula 360 km W of the nesting area. The Barnacle Geese from the newly established Tobseda colony have apparently pioneered a modified spring migratory routine, possibly partly under the influence of their shorter travel distance. The extended stay in the Wadden Sea fits with the trends in May census data over the past 15 years and may indicate that spring feeding conditions are better than formerly, that the Baltic staging sites are filled to capacity, or some combination of these factors.

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