Environmental Engineering Reference
In-Depth Information
is composed of both benthivorous (chiefly common scoter
Melanitta nigra
) and
piscivorous species of seabirds, while at Rødsand large scale bird migration takes
place both along-shore (waterbirds) and cross-shore (landbirds).
Tracking of Bird Movements
Real-time tracking of bird movements was made from shore by two observers.
As no selective tracking was applied, the obtained sample of tracks is considered
representative of diurnal migration patterns. Laser rangefinders (Vectronix 21 Aero®)
were used to collect three-dimensional species-specific data on migrating birds.
The laser rangefinder is comparable to a handheld binocular, but is equipped with a
built-in, battery driven laser system, which makes it possible to make recordings of
distance, altitude and direction to a given object. Under optimal conditions, laser
rangefinders can be used out to a distance of between 2 and 3 km for the largest bird
species, depending on the angle of view and on bird flight behaviour (gliding,
soaring or flapping). Laser rangefinders can be operated or “fired” with approximately
10-15 s intervals and positions and altitudes are logged automatically via a GPS,
and can provide long series of recordings for an individual focal bird or bird flock.
A horizontal radar was used for tracking two-dimensional movements at larger
distances, up to 2-6 km from the observer. One observer followed the tracks on the
radar screen, and recorded the information into a database. The second observer
attempted to find the objects in the field, using binoculars or telescope, and identified
species, number of birds and flying altitude using the rangefinder. Using the
horizontal radar, but adding species information by visual identification was
accomplished by a so-called “Real-time tracking” procedure, in which a dedicated
software program “BirdTracker” made it possible to draw/follow tracks of identified
individual birds or flocks on real-time videos from the horizontal surveillance radar.
The videos were produced using a frame grabber connected to the surveillance radar
and tailor-made software which provided the video as a background image on the
PC-screen with the radar position in the centre. A radar range of 6.0 km was used.
During tracking the PC screen was divided into two parts, the radar video and the
window to record data. Start and end time, number of nodes (location of fix) and
coordinates per node were recorded automatically.
Weather Model Data
For the purpose of analysing the influence of weather conditions on the migratory
behaviour of birds, modelled weather data from StormGeo was used (
www.storm.no
)
.
This regional weather model is based on the global weather model run by the
European Centre for Medium-Range Weather Forecasts (UK). The spatial resolu-
tion of the model is 0.1 × 0.1°, and the temporal resolution is 1 h. Zonal (U) and
