SEA TRANSECTS – What is that in the distance?

Author: Dries Engelen

One part of the LIFE Artina project is doing sea transects around the Lastovo archipelago to get a better understanding of the spatial distribution of (sea)birds during their breeding season. The transects are triangle-shaped and start and end at the border of the Lastovo Nature Park. From March to October we do twelve different sea transects each month and this is repeated for three years in a row. We dont only record the species, but also the number of birds and their behaviour, because for some birds the sea is an important place to feed or rest while for others it is not more than a large body of water they need to pass during their migration.

Sea transect 82/ 288; 3rd of April 2020

So here we are, me, Imogen (one of our volunteers) and our boatsman Stjepan of course. For the next three hours we will be cruising with a speed of 15 km/h doing the transect called TI. It’s 8:30 and the sea state is almost like a mirror (or bonaca as they say in Croatian). There are some clouds but other than that the visibility is great. ˝We see Mljet to the left of us, Sušac to the right, here we are doing a transect on sea-hea.˝ as Stealers Wheel would sing.

Island Sušac (Author: D. Engelen)

Anyway, despite the good mood and beautiful sea, our expectations of this transect are not too high. Previous transects to the south of Lastovo have often been pretty bare of birds namely. Surprisingly, within 5 minutes we observe a first bird resting in the distance. It’s a big gull, but too far to tell which species, and because of the chance of encountering Audouin’s Gull (Ichthyaetus audouinii) in these waters, we should be conservative and write it down as Larus spec. Some ten minutes later a similar observation. Half an hour goes by and the only other thing we see are two plastic buckets floating by. At this point the bird vs rubbish ratio is 2:2, pretty disappointing…

Audouin’s Gull (Author: N. Budageshvili)

Then, some 50 minutes into the transect, Imogen spots a low flying bird… it’s a Hoopoe (Upupa epops), or ‘zebrabird’ as she calls it! It’s quickly followed by a group of 15 Little Gulls (Hydrocoloeus minutus) going north. After 20 km from Lastovo we make a turn and enter the second part of the transect. Again Little Gulls! This time it’s a group of ~50 birds and they seem to be feasting on something in the sea. The feeding frenzy gets traversed by a group of 20 Cormorants (Phalacrocorax carbo), quite a nice sighting as the Lastovo archipelago is actually the kingdom of its smaller relative, the Shag (P. aristotelis). After some more bird observations, mostly gulls and some unidentifiable groups of distant migratoy passerines, we spot the first mammals of the transect. Three Bottlenose Dolphins (Tursiops truncatus) pop up close to the boat! Even if we see them more often around Lastovo, it always brings excitement to the observers.

We make another turn to do the third and final part of the transect. The sea is getting rougher and the wind is getting colder and is blowing straight in our faces. However, the surprising diversity thus far and the fact that Lastovo is slowly closing in on us, keep us motivated for the last 70 minutes. Our efforts get rewarded with some more nice sightings to spice up the day’s diversity, such as migratory raptors Marsh Harrier (Circus aeroginosus) and Kestrel (Falco tinnunculus), our third gull species of the day – Mediterranean Gulls (Ichthyaetus melanocephalus) in perfect breeding plumage – and three foraging Yelkouan Shearwaters (Puffinus yelkouan): one of the focal species of the LIFE Artina project.

Yelkouan shearwater (Author: B. Ječmenica)

At the end of the transect the sea is turning into bonaca state again, but even though it looks like we are floating over silk, the northern wind is still cold and continues to cut through our clothes. Luckily before our fingers lose all their feeling, we arrive at the lighthouse near Skrivena Luka and are finished! Ironically, now that the transect is done there are hundreds of Yellow-legged Gulls (Larus michahellis) feeding amongst a school of fish. Nonetheless, it seems that the southern transects become alive during spring (migration) time! It is exactly this, the element of surprise, which keeps you going during three years of sea transects. So, on to the next one (and the other 205 transects that are still to come) with hopefully some eagerly wanted observations, such as Storm Petrel (Hydrobatus pelagicus), Monk Seal (Monachus monachus) and Fin Whale (Balaenoptera physalus)!