Monitoring

How many Mediterranean Shags are there in Slovenian sea?

Mediterranean Shags can be observed during the whole year in Slovenian sea, but their number is very much fluctuating. In winter and spring, when most of them are on the Croatian breeding grounds, only a few subadult individuals stay in Slovenia. The largest number of Mediterranean Shags in Slovenian sea can be observed in late summer and early autumn. Then, their number raises even over 2.000 indivudals. In the project SIMARINE-NATURA we monitor their numbers and where they occure in Slovenian sea.

All together at night – monitoring at roosts

With regular monthly monitoring in the evening at three communal roosts (at Debeli rtič, at Strunjan and at Sečovlje) we study how many individuals are roosting in Slovenia and how their numbers fluctuate during the year. We count simultaneously at all three roosts which gives us quite accurate assessment of their numbers. By their plumage we can distinguish between adults and young therefore we can also study the age structure of the roosting communities.

Number of Mediterranean Shags at roosts

Scattered at sea during the day – monitoring by boat

In the morning most of the Shags move from the communal roosts at sea where they forage on fish. We monitor their daily occurence at sea with the ESAS (European Seabirds at Sea) method. This is a standardized international method for monitoring sea birds at sea, which also includes notes on their behaviour. With this method we can find out whether there are areas at sea which are especially important for life needs of the birds, especially their feeding. Besides Mediterranean Shags we also monitor other sea birds in Slovenian sea, for example the Yellow-legged Gulls (Larus michahelis), Mediterranean Gulls (Larus melanocephalus), Yelkouan Shearwaters (Puffinus yelkouan) and other. The monitoring is conducted by boat at 40 nautical miles (74 km) long transect. The boat is travelling with constant speed 10 knots (18,5 km/h). Along the transect all seabirds which swim in the water or fly over the area are being noted down and as well their behaviour, direction of motion, their prey if caught etc. These data will be mapped and statistically analysed and will help define areas at sea which are regularly visited by birds and are potentially appropriate for designation of Natura 2000 sites.

Density of Mediterranean Shags at Slovenian sea in July 2012

Methodology in details

Both monitorings are conducted by special protocols elaborated for this project. They can be downloaded here. (Available in Slovenian language – translation available on request).