ENR 5.6  Bird migration and areas with sensitive fauna

1   Bird migration

Bird migration occurs during the whole year, but culminates in the periods from the end of February until end of May, or beginning of June (spring migration) and from the end of August until October, sometimes even November (autumn migration).
The concentration of birds is also higher during some meteorological conditions such as Cyclone in Trieste bay, when the concentration of sea gulls increases, or in the time of bad weather (rain or snow), when birds land to rest or feed. Third condition is wet RWY, which attracts birds, especially river gulls.
Above field and forest areas there is constant danger of buzzards and falcons, which also prefer to concentrate around airports and RWY areas.
1.1   Spring migration
Spring migration intensity in period between February and June differs from the kind of birds. The number of birds is very different (gulls and geese in flock of few hundreds). Very noticeable movements are also very big flocks of swallows and jackdaws.
There is also a danger of cranes, which appear irregularly and sometimes in very large flocks of 30 to 50 birds and sometimes appearance of storks and herons in small flocks of 2 to 10 birds. Migration of birds is fluent during night or day time, depending on the sort of the bird.Movements are noticeable in the direction from Southwest to Northeast.
In the area of Ljubljana airport direction of movement is more Eastern, because of attempt of birds to avoid Kamnik mountains and because of attraction of area between Komenda, Mengeš and Duplica at Kamnik.
1.2   Autumn migration
Autumn migration culminates between end of August until beginning of November. It is not so recognisable as spring migration as density of movements is not so high. Direction of movements is from NE to SW.
1.3   Information on densities
There are some areas which are known as assembling of those birds, especially at the time of migration or in the case of bad weather.
This areas are, saline at Sečovlje, Koper bay, Vipava valley, lake of Cerknica, Marsh of Ljubljana, fields at Kamnik, Ptuj and Ormož accumulation, rivers Sava, Mura, Drava and all other water accumulation and open water surface, especially lakes and larger puddles.
1.4   Height of movement
Crows are flying mostly not higher than 150 m from GND in different densities, depending on weather or migration time. Flocks of smaller birds as finches are very often between 600 m and 800 m from GND. Big birds as falcons are in the vicinity of the mountains usually at a height of 1000 m to 1500 m from GND. At the area of Maribor and Murska Sobota there is high possibility of falcons and storks, which fly 300 m to 500 m from GND. In the spring time there is intensive flow of titmouse and sparrow around 1000 m above GND and in the autumn time crows, jackdaws and ravens.
Migration of birds usually takes place above height 500 m, with exemptions of rest landings.
1.5   Caution note
Permanent caution advised at aerodrome Portorož due to gulls and danger at the wet weather period (rain) at aerodrome Ljubljana due to danger of river gulls and jackdaws. At Ljubljana airport also permanent caution advised due to falcon danger. During night there is permanent danger from GND to 100 m of owls, especially in the vicinity of the forests.
1.6   Reporting of bird strike
To achieve more comprehensive statistics of Bird strike, the Ministry of Infrastructure and Spatial Planning, Civil Aviation Directorate (DCA) wants to collect information about this from the civil aviation. All pilots on flights within LJUBLJANA FIR are therefore requested to report all cases of Bird strike or incidents where a risk of Bird strike has been present to the Ministry of Infrastructure, Civil Aviation Directorate (DCA).
For the use of reporting a BIRD STRIKE REPORTING FORM has been produced (ICAO DOC. 9332-AN/909). This form may be obtained from airport offices at public aerodromes or from the Ministry of Infrastructure and Spatial Planning, Civil Aviation Directorate (DCA).
Remark: All data will be updated according to the latest statistic data obtained by Bird strike report.
Chart Bird Migration Routes (ENR 6.4-1) shows the main migration routes and chart Bird Concentration Areas (ENR 6.4-3) the main assembling areas.

2   Areas with sensitive fauna

2.1  Many species of birds as well as mammals are sensitive to noise from aircraft and overflying their breeding and resting places may be critical. Overflying of such areas
2.2  The area is shown on the Sensitive Fauna and Flora Area Chart, see ENR 6.5-1.