Table 6.2: Number of tracking devices mounted on seabirds Audouin’s Gull
Mediterranean Shag
19
24
GPS dataloggers
8
8
Geolocators
5
Tracking method Radio-tags
Yelkouan Shearwater
16
2
5
Compass dataloggers Number of colonies
Cory’s Shearwater
3 6
5
4
1
in Greece, were taken in consideration. Overall, radio-tags, geolocators, GPS dataloggers and compass-data loggers were mounted on Audouin’s Gulls, Mediterranean Shags, Cory’s Shearwaters and Yelkouan Shearwaters at 16 colonies in the Aegean and Ionian Sea (Table 6.2).
6.1.3.1 Radio-tracking Radio-tracking using radio-tags was the main method for tracking individual Audouin’s Gulls and Mediterranean Shags. Radio-tags were mounted on birds trapped at their nesting sites early in the breeding season. The tagged birds were then tracked during the rest of the breeding season and post-breeding season. Individuals equipped with radio-tags were initially tracked by mobile antennas from land. However, due to low reception range at sea level, the majority of tracking was carried out from a speed-boat which followed the course of the birds, coupled by fixing of location using a handheld or boat GPS device together with visual recording of the tracked birds’ behaviour. The latter approach overcame the restrictions of standard radio-tracking, such as limited reception range, medium accuracy and limited information on seabird behaviour. It also provided the high spatial resolution required for the delineation of marine IBAs for Audouin’s Gulls and Mediterranean Shags, most of which were relatively small in size.
Radiotracking from land 54
Mediterranean Shag equiped with a radio-tag
Radiotracking at sea