Info received from Declan Troy, Troy Ecological Research Associates,
Anchorage, Alaska, (slightly edited).
The Pomarine Jaeger (Stercorarius pomarinus) is a specialized predator while
on its arctic breeding grounds. Nesting occurs only in areas experiencing
peaks in lemming (Lemmus) abundance, the primary prey. This leads to large
fluctuations in
nest densities to the extent that 3-4 years can elapse between significant
breeding events at a given location.
The species is thought to be nomadic, moving to new nesting locations
searching for lemming peaks. Outside the breeding season Pomarine Jaegers
are pelagic. Their nomadism during breeding and marine distribution
movements make tracking
using conventional methods challenging, thus limiting any detailed
understanding of Pomarine Jaeger migration.
The summer of 2004 was a breeding year for Pomarine Jaegers in northern
Alaska providing the opportunity to investigate the feasibility of tracking
this species using satellite telemetry. Four birds were trapped at their
nests near Barrow, Alaska (71°N). Their 18g solar PTTs were attached with
strips of Teflon ribbon forming "fanny-pack" harnesses. All the birds
remained near their nest sites into September then exploded away from
Barrow. The birds dispersed widely to the extent that during much of the
fall there was an individual in each quartisphere of the globe (all in the
Pacific Ocean). The migration of one individual is illustrated. This bird
quickly crossed into the eastern hemisphere and remained in Russian waters
until reaching Japan. It loitered around eastern Japan until mid-November
then proceeded rather directly south though the Solomon Islands to
Australia. This individual made a U-turn around 35°S (south of Sydney) and
back-tracked north off the Australian coast. In total, the fall migration
from Barrow to the southern limit of its movements was approximately 15,000
km. The reversal in direction was thought to be a local movement rather than
the start of spring migration but this will remain unknown as contact with
this individual was lost in February 2007. Although our knowledge of the
movements of this bird were terminated prematurely it transmitted long
enough to allow us to add Pomarine Jaeger to the short list of birds known
to migrate between North America and Australia.
Mike Carter
30 Canadian Bay Road
Mount Eliza VIC 3930
Tel (03) 9787 7136
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