Is this a first for tracking analysis? And more on UV

UV is still at the southern end of the Gulf of Cintra. Paul identified him almost certainly ‘plunge-diving’ to catch an early supper on Monday. In Paul’s words.

It’s very seldom that we can spot the moment when an osprey plunge-dives to take a fish, just by looking at the satellite tracking. In fact, it may never have been done before.

This is that exact moment.

On the afternoon of 15.12.14, UV is on the south side of Gulf of Cintra,
flying along the beach at around 25 metres height. At 15:38 he spots
something, turns back towards it, drops down at 15:40 and then climbs back
to the same height. We know he went into the water because the temperature
telemetry from his tracker – which has been steady at around 24 DegC,
suddenly falls by five degrees.

But how do we know he actually caught one?

As soon as this hunting pass is completed, UV flies 900m inland, where he
stops for over an hour at ground level. Having presumably finished his
dinner, he then flies direct to his roost site (which is 12 km to the
southeast, among high dunes) arriving there at 18:35. He does nothing else
that evening.

UV fishing Courtesy Paul Wildlifewriter

UV fishing
Courtesy Paul Wildlifewriter

Many thanks to Paul for this great insight, and for more weather research today.

Since Wednesday’s post UV has remained on the SW side of the Gulf of Cintra and today is even further SW. But before discussing that, a couple of interesting points about his behaviour. On 17 December he was at the coast by 09.00 and spent most of the time around the shore, with one excursion about a km out to sea. Heading back inland he had a short roost then a long one for about 4 hours until just after 17.30. The image below shows both points.

Moving to keep in the shade?

Moving to keep in the shade?

You can see that during the longer stop UV is on the NE side of a large dune. He moved gradually along in a mainly E/SE direction – was he keeping in the shade?

From 14 to 16 December he used the same dune further inland for his overnight roost, but after starting off on it yesterday he moved in twilight to a new spot. From the image below it seems no better than his ‘usual’ one, although the landscape may not be quite the same now as when the image was captured.

Overnight roosts

Overnight roosts

Today he started moving towards the coast sometime after 09.30 but did not reach it before the data downloaded at 13.40. He was south of the headland, so outside the Gulf of Cintra, on the west side of a large dune. Although he sometimes doesn’t hunt until the afternoon he may have moved to this new spot because of the weather. The wind is from the east, and there were several large sandstorms inland south and east of UV. It is possible that more minor dust streams  have reached UV’s area in the airflow. So he may need to keep hunkered down for a few hours.

The unpredictable sandstorms at this time of year are a good reason why UV may be well advised to head south, but then again he could encounter them en route. Worry, worry!

Here is an image from early afternoon on 16 December until about the same time today. The yellow bull’s eye is the last fix before the download.

UV's range pm 16 Dec to pm 18 Dec

UV’s range pm 16 Dec to pm 18 Dec

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A brief bit on 7H

Remember 7H, the Nest 2 female juvenile with a likeness for a particular pond and plenty of pylons? With UV’s journey from Portugal to Western Sahara and his second stopover she hasn’t had a mention for almost a couple of weeks. All seems well with her despite some poor weather in Morocco, especially over the weekend and until 16 December. There was some rain every day, with the worst day being Sunday. She has ranged over a small area with not many visits to either the pylons or pond. Here are a couple of images of her last week or so.

7H on 9 and 10 Dec

7H on 9 and 10 Dec

No visits to pond or pylons either day when the weather was reasonable. Next, a longer period.

7H range 11-17 Dec

7H range 11-17 Dec

She roosted overnight  on the pylons twice in this time, once when it was dry and not especially windy, once when it was wetter. She visited the pond only briefly. Fixes are relatively infrequent, about every 30-40 minutes most of the time which mainly reflects her lack of activity.

So she seems very settled But then that was how UV seemed on the morning of his departure!

There will be a blog about him later which will include another piece of great detective work by Paul Wildlifewriter.

 

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UV: at second stopover still!

Before covering what we know of UV’s activity since the last post, here is an image provided by Paul showing UV using the flying technique known as ‘crosswind tacking’ as he pushed across to the coast last Thursday. You can read about other techniques in recent articles on Paul’s blog, some of which include data from the Kielder tracked juveniles.

UV 'crosswind tacking' in the Sahara Courtesy Paul Wildlifewriter

UV ‘crosswind tacking’ in the Sahara
Courtesy Paul Wildlifewriter

A further image from Paul illustrates a probable fish catch during UV’s Friday afternoon on Bajo Tortugo. High tide that day was at 17.40 UTC. (UTC is the same as GMT.)

Probably a successful catch Courtesy Paul Wildlifewriter

Probably a successful catch
Courtesy Paul Wildlifewriter

Moving forward in time, we left UV still at Bajo Tortugo early on Saturday. In the aerial photo of the Gulf of Cintra here; you can see the lagoon area on the left of the shot. UV stayed in that general area all day. His lack of activity reduced the number of fixes so at best they were around every 15 minutes, but he can’t have gone much further than the limits shown on the image below.

UV on 13 Dec

UV on 13 Dec

He left the western edge of Bajo Tortugo by about 16.00 GMT as soon after he was on the 12 December overnight roost. He moved further north by 18.11, shortly before sunset, but this was not his final roost. By 19.09 he was another 500m NE, his final journey of the day and made in nautical twilight.

On 14 December he appeared to remain at the roost site until well after 09.00; the first activity was a fix where he was crossing the Gulf of Cintra. This was at 09.54 and the next fix was 10.33 when he was stationary on the SW side of the Gulf a little way inland. He was in the same general area until just after noon when he moved slightly further inland for over an hour before going to the shore line and possibly fished as his speed was under 2 kph in consecutive fixes just offshore. Below is an image of his activity near the sea in the afternoon, which lasted less than 20 minutes. His longer roosts inland are the darker fixes, more obvious if you click to enlarge the image.

Catching lunch? Less than 20 mins at the shore

Catching lunch? Less than 20 mins at the shore

UV roosted near a track in the desert (the bottom point in the image above) until just after 16.00 when he flew initially in a SSE direction then adjusted to SSW as he reached 507m altitude before descending. Paul identified a frontal system passing over at sunset, which was at 18.20; just at that time UV moved a very short distance, maybe to a more sheltered spot in the dunes which probably have changed since the Google Earth image was captured. Here are the two roosts.

UV moves from one dune to another at sunset

UV moves from one dune to another at sunset

Did UV move over the Gulf because he was intending to head away from the stopover? The data on 15 December came in very early and he hadn’t left the roost. As this post was nearly finished it wasn’t clear if there would be data today – if he had continued his migration yesterday he could well be out of cell tower range.

But then an e-mail arrived, showing him exploring the SW corner of the Gulf over the past couple of days. Fish will be relatively easy to spot in the sheltered water near the headland. His behaviour both days has been similar with his journey to the water punctuated by long stops; the longest for each day have pins. On both days he arrived at the sea around 15.00. Yesterday he was only there for about 30 minutes before heading inland; today he was still there at the last fix at 15.16. Here is an image showing UV’s travel yesterday and today until soon after 15.00.

UV activity 15 and 16 Dec

UV activity 15 and 16 Dec

He doesn’t seem to be getting ready to move on. But there weren’t any signs of that in Portugal either!

 

 

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UV and the Gulf of Cintra

A data update came in early on Saturday for UV. And yes, he was continuing his mini-stopover in Western Sahara. A first, possibly, for an osprey from the UK (although are two nights an ‘official’ stopover) or will he stay? A tracked Swedish osprey overwintered about 200 km further north in Western Sahara.

Analysing his time on the bay south of Dakha shows some interesting aspects. But first here is some background, thanks to Paul Wildlifewriter for most of it. The bay is the Gulf of Cintra although it isn’t named on Google Earth. It is possibly still an important breeding ground for one of the rarest and critically endangered seals in the world, the Mediterranean Monk Seal.

UV is favouring a small area, more on that in a moment, but 2003 Google Earth images show there used to be a fishing village at the extreme SW on Puntillas de las Raimas. Paul has written about it here, well worth clicking through to read,  but for now here is a 2003 image showing the village at bottom left and also UV’s movements nearby.

Gulf of Cintra and the fishing village

Gulf of Cintra and the fishing village

UV arrived at the bay just before 17.00 GMT on 11 December after flying over desert. The sight of water must have been welcome, despite that long sea crossing on 7/8 December. At 17.14 he was over the sea, then ten minutes later was stationary on the beach. He explored up and down the central area of the bay before heading off NNW inland shortly before sunset. That night he used three roost points, shown on the image below.

UV roosts overnigth 11/12 Dec

UV roosts overnigth 11/12 Dec

The altitude readings indicated he could be on structures, but none are clear on Google Earth so they may be natural features.

On 12 December he was up at the coast by 08.20, and the next series of fixes (roughly 35 mins apart) showed him travelling down the shore until at 12.23 he was over the sea at the top of Puntillas de las Raimas – the most westerly point in the first image.

He went inland briefly but was soon back to the coast and all afternoon he frequented a small area with lagoons – Bajo Tortugo, or Bay of the Little Tortoise.

UV on the afternoon of 12 December

UV on the afternoon of 12 December

The red dots which appear bolder (more obvious if you click and enlarge the image) are ones where he spent between around 30 minutes and an hour. Were some of his moves caused by Mediterranean Monk Seals ‘inspecting’ him? We’ll never know but more probably he was moving as the tide altered the landscape.. The bold dot on the extreme left looks as though he was in the water, but historic images show a sand bar there.

Between 17.25 and 17.48 he flew inland and established his overnight roost. Almost certainly on a pole for telephone lines. 7H would approve of the use of man made structures! On the image below you can see the white dots which are the foundations for the poles, and also the distance between Bajo Tortugo and his roost.

UV's roost 12 Dec

UV’s roost 12 Dec

On 13 December he left the roost area between 07.15 and 07.57, when he was flying near the sea – the yellow bull’s eye in the close up image of the lagoons. Quite an early start as sunrise was 07.37. What next, we wonder? No e-mail yet (16.00) so perhaps he has moved on.

Even if he did stay only a couple of days it was interesting to follow his behaviour – sweeping the bay to the south immediately on arrival, roosting inland then flying slowly down the coast on the west before focussing on what is almost certainly the most productive area for fish.

 

 

 

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UV, one very interesting Osprey

There was another data drop from UV late today, again unexpected given lack of cell towers in Western Sahara. But as soon as the data file opened it was clear how this had happened. He has gone nowhere! Here is an image of him today.

UV hangs around the bay

UV hangs around the bay

That northern part of the bay is the area fish are most likely to be. His decision to stay could be wise because there is a large dust storm (equalization event in techspeak) in the mid Sahara. Thanks to Paul for this info.

Also today the backfill data on his journey from Portugal downloaded. Here is his sea crossing.

UV sea crossing to Africa

UV sea crossing to Africa

He flew non stop over ocean for just over 24 hours. And covered about 1100 km. But he didn’t pause when he reached Africa, carrying on (with possibly one very brief halt at 14.48) until 16.49 GMT.  He then roosted on the desert floor until sometime after 10.00 on 9 December when he set off again flying without a break (as far as quite frequent fixes show) until 15.50 when he had a half hour stop in the desert, then he flew a bit further before finding an overnight roost. Here is an image of the area.

 UV overnight roost 9 Dec

UV overnight roost 9 Dec

The rest is history, as they say. He left the roost area at soon after 10.00 and was within range of a cell tower later that day which is when we first knew he had reached Africa.

The final image shows his overall travel from leaving Portugal until tonight. In that time he has flown about 2000 km.

UV from Portugal to Western Sahara

UV from Portugal to Western Sahara

 

 

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FLASH 2! More data on UV, unexpectedly

Resigned to a couple of data-less days given limited cell tower coverage in Western Sahara it was a welcome surprise to receive news a short while ago. Here is what UV did today!

UV's travel 11 Dec

UV’s travel 11 Dec

The roost point was actually the second of two on the desert floor. UV then had a bit of a lie in, setting off between 11.30 and noon GMT.

As Paul predicted, the easterly winds almost certainly affected the route. Again UV flew strongly at up to 70 kph and at altitudes of over 1000m.

This image shows him either trying to catch supper (there is surf fishing in the area, here is some info and photos of some tiddlers at Dakhla, a bit further north) or else looking for a suitable cliff to roost on.

UV at the coast

UV at the coast

 

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FLASH! UV is in Western Sahara

The last post mentioned that no other UK osprey was known to have had a longer stopover than either UV or 7H, which was perhaps an indication that they would overwinter in Portugal and Morocco respectively.

Well, by mid afternoon today, 10 December, UV was flying SSW over Western Sahara. And travelling at pace.

Most of the data is missing for his journey. On Sunday the last fix showed him about 14 km off the SW tip of Portugal. He had gone out to sea about 100 km further north, so it did look as if he might be moving on.

There has been no data since then until this afternoon, and given his location we are lucky to have received the very limited download that came in. Here is an image of the gap!

A large gap in data between 7-10 December

A large gap in data between 7-10 December

And here is a closer view of the travel today between 12.50 and 15.17.

UV during just over 2 hours today

UV during just over 2 hours today

Paul Wildlifewriter (to whom my personal thanks for keeping me as sane as possible during a worrying time) has provided daily weather information. The winds have been mainly NNE during his onward migration, so roughly tailwind. There was a clear night and the moon was just past full on Sunday, which must have been spent over the sea. (No ships appeared to be in the area!)

Hopefully more data will backfill when he reaches cell towers again. Which could be quite a while.

Paul also noted that yesterday there was a diurnal sandstorm on the coast of Mauritania: satellite imagery showed the dust being blown out to sea. Fortunately that has now subsided and UV was about 500 km away at last fix. He was flying strongly during the data window, speeds at up to 66 kph, and at altitudes up to just short of 1000m.

Since Sunday he has travelled at least 1570 km – that is the straight line measurement. He is about 900 km from the Mauritania-Senegal border. The winds will be less favourable tomorrow, more easterly and fresher. Paul has estimated that if he maintains today’s heading and with the wind direction he could arrive at the Banc d’Arguin, a UNESCO World Heritage Centre and migration hot spot.

Keen osprey followers will be aware that UV’s route is probably quite similar to those of Millie, the 2014 Loch Garten juvenile currently wintering on the Mauritania-Senegal border, and Alba, a 2012 juvenile from that nest. How similar can only be determined if the missing data is backfilled.

Tomorrow there will be a post with a bit more about UV’s time in Portugal. Which is now the record for a stopover for a UK osprey, as far as is known.

 

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