Migration and breeding biology of Arctic terns in Greenland

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3 Future research
The study on the long-distance migration of the Arctic tern (Manus I) revealed
a number of new facts not previously known about the impressive
annual migration and verifi ed existing knowledge obtained from ringing
recoveries. This study also raises some new questions that would be interesting
to pursue in future studies: 1) at the breeding areas, the Arctic
tern is known to be on the wing most of the time. When it rests, it sits
on the ground or alternatively on an iceberg. Unlike most other seabirds,
the Arctic tern rarely rests on the water and only in very calm weather.
The geolocators used in the migration study also record dry or wet condition
during the period of deployment, which can be used to indicate
the individual’s behaviour during migration (Guilford et al. 2009). From
a both physiological and energetic perspective it could be interesting to
investigate whether Arctic terns manage the long stretches of migration
between the polar areas without long periods of resting on the water; 2)
The migration study identifi ed a divide into two different southbound
routes. This divide could be coincidental, where wind systems drive the
birds to take a western or eastern route. This would mean that the same
individual may migrate south by either of the two different routes each
year. An alternative explanation would be that the route may be genetically
coded or learned in the individual and the same bird will choose the
same route each year. The geolocators have the capacity to log for two
years and are cable of storing data for up to ten years. In theory, loggers
applied in 2007 and not retrieved in 2008 (potentially up to 40 loggers)
should contain data on two round trips which could help shed light on
which of the two hypotheses is most plausible. An attempt to retrieve loggers
at Sand Island was made in 2009, but was unsuccessful due to a year
of breeding failure. Hopefully, an attempt in 2010 will prove to have more
success; 3) The migration study identifi ed an area in the central part of the
Atlantic Ocean to be of high importance for the terns on their southbound
migration. It seems likely that this area may be important for other surface
feeding seabirds as an at-sea foraging hot-spot, and it could be interesting
to expand the number of study species in a migration study using geolocators.
Such a study could prove to be an effi cient tool to identify at-sea
areas of high biodiversity otherwise diffi cult or cost-prohibitive to obtain.
Although the study on relaying in Arctic terns (Manus III) did produce
estimates of the species’ ability to produce a replacement clutch when the
fi rst clutch was removed, additional detailed information is needed in order
to address the impact of harvesting and relaying at the population
level. However, large logistical diffi culties are associated with a study of
this kind. Relaying Arctic terns may easily move within or even well out
of the colony to place their new nest. The chances of detection of the new
nest site, and establishing an accurate estimate of what proportion of the
population will relay, decreases with distance from the original nest site.
Unless devices, such as radio transmitters, that are able to track the location
of the bird in a study are used, it will be diffi cult to obtain accurate
estimates of relaying in Arctic terns.