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Bird Ringing for Science and Conservation
The EURING Swallow Project
A worldwide symbol of bird migration all across
its vast geographical range and for different human cultures, the
Barn Swallow is also an important bio-indicator for habitat types
which are under threat in different continents.
It breeds colonially in farmlands, sharing this
habitat with a concentration of bird species showing worrying population
declines.
Before leaving the northern hemisphere for its
long migrations, the Swallow stores energy reserves during a
crucial roosting phase, when the birds congregate at dusk in reedbeds,
again a habitat which is facing severe reduction at a global scale.
Roosting behaviour is also typical of the winter
period spent in the southern hemisphere, in vast areas of sub-Saharan
Africa for the Western Palearctic populations. These areas of reeds
and elephant grass are also under threat from human activities and
agricultural development.
The fascination of its journeys makes the Barn
Swallow a very popular research subject among ringers. For all these
reasons the EURING Swallow Project (ESP) was launched in 1997. During
five years of activities on the breeding grounds, as well as along
the migratory routes and on the wintering grounds, nearly one million
Swallows have been ringed by many hundred ringers in 25 different
countries in Europe, Africa, and Asia. This amazing effort has allowed
the unravelling of different aspects of the lifecycle and migrations
of what used to be
regarded as a very well known species.
One million Swallows ringed in 25 different
countries have shown
the potential of large-scale EURING projects as a basis
for
scientifically sound international conservation policies.
The large-scale geographical coverage has also
offered a unique opportunity to test optimal migration theories.
Data gathered in Italy could confirm a tradeoff between the completion
of body moult and the accumulation of fat reserves during the pre-migratory
roosting phase. At an intensively studied roost in northern Italy
it has been shown that birds can only start accumulating fat when
their body moult approaches its final stages. Optimal migration
theory also predicts that birds will reach their final departure
conditions just before embarking
on the crossing of possible ecological barriers, like the Mediterranean
and Sahara for European Swallows flying
to Africa. By analysing data gathered from Finland southwards across
Europe it has been possible to confirm this theory. Swallows leave
Finland still with reduced fat stores, which are quite larger already
in birds analysed in Switzerland. Still across Italy and Spain,
the amount of fat reserves in birds in the north of these countries
is significantly lower than that of swallows leaving the southernmost
latitudes.
Even though it
had long been thought that an aerial feeder like the Swallow
would not need to store fat before migration, but rather adopt
a “fly and forage” strategy, the project has shown
that the amount of fat accumulation in European Swallows matches
that of other long-distance songbird migrants.
The network of EURING Swallow Project roost
ringing sites has also offered the first confirmation based
on field data, that the amount of fat reserves at departure
towards Africa is correlated to the distance that first-year
and totally un-experienced swallows will have to fly across
ecological barriers they have never seen before. |
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The Swallow - a symbol of international
co-operation
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Young swallows leaving southern Iberia, which
will cross the narrow stretch of the westernmost Mediterranean and
the Western Sahara, will depart with lower fat reserves than those
of swallows leaving southern Italy. Those departing from Italy will
fly a long distance over the sea and across the widest part of the
Sahara desert, and are in fact much fatter. The huge number of Swallows
ringed during the project has also produced a large number of recoveries
and described yet unknown wintering quarters for different geographical
European populations. This has also led to increased action for
Swallow conservation in Africa, where huge numbers of birds were
and still are killed for food in Nigeria, Central African Republic,
and Congo.
Thanks also to the EURING Swallow Project, the
Swallow is now, more than ever before, a global symbol not only
of bird migration but also of the need for internationally based
conservation efforts and strategies.
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