Doi: http://dx.doi.org/10.13157/arla.64.2.2017.ra2
Authors: Michele PANUCCIO, Antonino DUCHI, Giuseppe LUCIA and Nicolantonio AGOSTINI
E-mail: panucciomichele@gmail.com
Published: Volume 64.2, July 2017. Pages 305-324.
Language: English
Keywords: Bosphorus, Dardanelles Strait, raptor migration, Turkey and weather
Summary:
Afro-Palearctic migrants move between breeding
and wintering grounds along flyways determined by several factors (bird
morphology, geography, behavioural adaptations) and raptors often concentrate
at straits to avoid long sea crossings. Here we test the hypothesis that raptor
passages across different areas of the Turkish Straits are similar in species
composition as well as flight behaviour. We made simultaneous observations at
the Bosphorus and at the Dardanelles in autumn 2010. We tested the influence of
weather, time of day and flock size on the intensity and spatial shift of
migratory flow as well as the tendency to cross the Dardanelles Strait rather
than follow the peninsula. We also collected information of the flight altitude
of raptors using an optical range finder. The species composition observed at
the two sites was completely different, with eagles predominating at the
Bosphorus and small and medium-sized raptors predominating at the Dardanelles
Strait. Compensation for wind drift at the Bosphorus was species-specific, with
small and medium-sized raptors showing a drift effect by crosswinds, and eagles
showing compensation and overcompensation. Mean flight altitude was similar
among species, while the response to weather conditions varied, being mainly
affected by wind. In the case of Short-toed Snake-eagles, flight ability and
response to weather conditions was also age-dependent. These results show that the
flight strategies of migrating raptors are species-specific even if some flight
parameters may converge as a result of risk minimisation. The differences between
species and flyways probably reflect interspecific differences in the ability
to fly over water.
