16.09.21 – Concluding remarks
Reality check: the initial phase of our Yelkouan program is now drawing to a close … due to the natural ‘death’ of our transmitters which survived anyway much beyond our wildest expectations.
Here are some key findings that clearly make a success of our eleven-week investigation. Some were totally unsuspected.
We have identified for the first time a seasonal axis of connectivity between the Adriatic and Black seas via a seabird species that leaves its nest in the central Mediterranean to travel as far as the northeastern corner of the Black Sea. The migratory flights of our tagged individuals were all distinct in time (asynchronous) but very similar in their trajectories, with the added discovery that they never flew overland, even avoiding the major shortcut offered by the Canal of Corinth. What are their main navigational tools ? The triggers for their individual departure ?
Expending such massive energetic costs (flying over 3,000 km a few meters above the waves !) is more than compensated by reaching the spawning grounds for millions of anchovies – the main staple food of the Shearwater – near the Azov Sea.
The individuals found migrating in our study did not exclude juveniles, born a few weeks previously. Are they travelling with parents ? With other elders ? With other juveniles? Other individuals studied were still flying in the north Adriatic when we lost, one by one, their signal. Distinct migration strategies ? Or just a delay in taking off for the Black Sea?
We have just retrieved the signal of A8 which made its entry into the Black Sea a week ago. After a foray in the open sea, it is now resting/flying (?) offshore close to the fishing town of Sinop on the Turkish side.
As we anticipated a few days ago, A8 finally made it to the Marmara Sea late yesterday.
It must be now in the Black Sea … which brings to five (A2, A7, A8, A11, J3) the number of Yelkouan that we tracked successfully all the way from their start in the central Adriatic two months ago.
Bingo ! Over two weeks ago, when we lost track of J3 near the entrance of the Dardanelles, we expressed the hope that ‘our’ bird had crossed the straits into the Black Sea prior to our next rv with the satellite. We were right : now this 4-month juvenile has reappeared near the Azov Sea, emitting distinctly and thus enabling us to precisely draw its recent North North East itinerary across the Back Sea. This is the first evidence to our knowledge of a migration by a juvenile yelkouan (likely led by an elder during its journey).
A8 appears to make its move towards the Marmara Sea (and ultimately the Black Sea).
We are keeping a close watch
During the past 48 hrs, a series of events unfolded which lead us to suppose (educated guess) that both A11 and J3 are now safely in the open Black Sea, far away from GSM relays. This is quite remarkable in the case of J3 – a 4 month juvenile – which left the fires in the region of Athens three days ago, crossed the Aegean Sea in direction of the Dardanelles Strait in less than 24h, and then likely crossed the Marmara Sea before our early morning rv with the satellite. Which is where we lost its signal, as happened before with A7 and A2, with the hope to retrieve some day.
A11 may be a late starter… but what a record flight… already in the Sea of Marmara in the space of three days!
A11 appears ready (at last) to leave the Adriatic. It is one of the eleven birds still emitting.
03.08.21 Where are we now ?
A quick synthesis, one month after ‘our birds’ took off from their nests in Croatian waters, appears in order. Two of ‘our’ Yelkouan (A7, A2) reached the Black Sea. We are still connected to A7 which clearly enjoys this anchovy-rich area near the entrance of the Azov Sea.
J3 is extending its stay in the Cyclades islands, where Yelkouan colonies abound. Most of the others never left the Adriatic (will they eventually migrate south?), although A9 and A1 are perhaps showing signs at last of moving out of the area.
Some of our emitters are showing signs of fatigue. It seems that we have lost the signals of A3, A5 and A10.
Stay in touch!
The past few days have consolidated the latest trends observed, with A7 positioned at the entrance of the Azov Sea (presumably feeding on tons of young anchovies), A2 is still missing in action somewhere in the Black Sea, and J3 our most advanced juvenile in the same area of the Aegean as A5.
BREAKING NEWS!! A7, our ‘front-runnner’ who reached the Black Sea on 14 July to disappear immediately from our radars, has just re-appeared late this morning in the vicinity of the Strait of Kerch where it was detected at last by a coastal GSM sensor. We retrieved not just its current position, but also his stored SW/NE route across the Black Sea during the past 12 days. To our knowledge this is the first confirmation of a Yelkouan migration from the Adriatic Sea to the mouth of the Azov Sea. Our early hypothesis that this bird underakes such a long journey in order to take advantage of the millions of sprat (young anchovies) present until October in the northeast Black Sea / Azov Sea appears validated. Hopefully A7 will continue to share with us his regular progress (will it enter the Azov Sea?) in coming days. We’ll keep you posted.
J4 left the Adriatic Sea and is now approaching the gulf of Corinth. Will he join the wide area of the Cyclades which J3 seems to like?
Is A9 ready to start its migration or is it just exploring for the first time the western shore of the Adriatic?
→ 11:30: Bingo! A2 concluded its non-stop flight across the straits and the Marmara Sea yesterday and reached the Black Sea just before sunset! Luckily for us, he/she has the ‘good idea’ to rest on the water during the night, just at the limit of our satellite coverage. We were therefore able to retrieve its track at the time of our 3:00 a.m. (GMT) rendez-vous with the satellite. We lost its signal since… With luck we will be able to locate it soon again (?) unless it is now flying over the high sea.
→ 17:30: Breaking news!! A2 did find its way into the Marmara Sea! Hopefully the satellite will not lose its track when it enters the Black Sea (most likely), five days after A7.
→ 11:30: We are now zooming our attention on three birds:
A7, still ‘missing in action’ over the Black Sea;
A2, which seems to search the narrow entrance of the Dardanelles strait;
J3, well engaged in the Aegean Sea, who surprises us by undertaking a ‘migration’ as a 2-month-old while the three other juveniles still linger in the south Adriatic Sea.
16.07.21 → We lost track of A7 on Wednesday morning (right upon its entry into the Black Sea) but not the hope to retrieve its path in a few hours (days?) once he gets closer to a GSM antenna on the mainland.
A5 is the likely candidate for the next crossing of the Dardanelles and Bosphorus straits. But when? We follow that closely.
Two of our juveniles (J1, J3) are now almost in sight of one another, at the south of Corfu while J2 and J4 still linger in northern Albanian waters. For how long?
15.07.21 → A7 has disappeared from our radar since he emerged out of the Bosphorus into the Black Sea 24 hrs ago. Hopefully it is simply because it is flying across towards one of the main anchovy spawning grounds in the region (Crimea, Sea of Azov, or central Anatolia). We should know fairly soon once a coastal GSM sensor picks up the signal.
Otherwise A2 is getting closer to the entry to the Dardanelles Strait.
14.07.21 → A7 has now arrived in the Black Sea, after having crossed the Dardanelles, the Marmara Sea and now the Bosphorus in the last 24 hrs hardly without stopping… Its trajectory so far appears optimal: it took him exactly one week to fly over 2’000 km since leaving its nesting site in Croatian waters !
This is quite a feat, compared to other Yelkouan on our radar (A2, A5) which have paused (or ended their journey ?) in the Aegean Sea, in the vicinity of known Greek colonies. For how long?
All the juveniles are back on our radar, but are making little geographic progress at this time.
Where will A7 go now? Hopefully we shall receive his signal for a while more and so gain key information about the wintering zones of (some) yelkouan shearwaters.
13.07.21 → A7 has just entered the Dardanelles Strait!
12.07.21 → A7 continues to lead the way (presumably towards the Marmara and Black Seas), having left Mytilene island a few hours ago. Will it now engage directly into the narrow entrance of the Dardanelles Strait – some 150 km north? Key question, considering that the yelkouan avoids flying overland.
We (temporarily ?) lost the signal of our juveniles J1 and J2 over the south Adriatic and northern Ionian Sea. We hope that they will reappear soon on our radar screen. On the other hand our fourth juvenile J4 made its first appearance.
11.07.21 → A7 is the most active right now, pursuing his advance towards the north-east in the direction of Chios; will he cross between the island and the mainland?
10.07.21 → Some movements in the last 24 hrs !
Three adults in or near the Aegan Sea: A5 has now resumed its journey towards the north, finally bypassing Andros island. A7 is not far behind, with a more direct NE trajectory, whereas A2 is making a long pause southwest of Athens.
Three juveniles are now on our radar as J3 has emerged of its burrow and is flying close to the nesting site. J1 has bypassed Corfu, and J2 – seemingly a day or two behind – has entered Albanian waters.
09.07.21 → Our most active adults (A2, A5, A7) are clearly pursuing their migrations. Where will they stop?
A second juvenile (J2) is showing early signs to leave the Adriatic on the tracks perhaps of J1.
08.07.21 → A5 is well ahead in the mid Aegan Sea (will it stop here or pursue towards the north?)
A2 has now entered the Aegean Sea and is not far behind.
A7 passed the strait of Otranto during the night and is now south of Corfu.
J1, only a few weeks old (!), left behind its nesting site ca. 500 km north. Do juveniles migrate? (they fly solo presumably)
07.07.21 → Two adults (A2 and A5) are now well engaged in their migration, having reached the Peloponese, one day apart. Most of the others still hover around their colony site in Dalmatian waters but some have crossed the Adriatic westward to forage near the Italian coast. Will they soon migrate to their wintering site(s)? Two of the four juveniles (J1 and J2) tagged have started to explore the area between their nesting site in the Lastovo Archipelago and Dubrovnik. We have no data yet from the two other juveniles (probably still in their burrows and therefore not transmitting).