Osprey AW

Male Osprey AW fledged from the Site B nest in 2006. He bred for the first time in 2010 at Site O (a nest on private land near Rutland Water) and again in 2011 with a Scottish female from Argyll. AW then spent several months wintering in Africa, but in February 2012 his transmitter stopped sending data. Subsequently he failed to return to Rutland for the 2012 breeding season.

AW flies to Liberia, and maybe beyond!

All of the adult Ospreys tracked from the UK during the past decade have returned to the same wintering site each year. Once back at their regular winter haunt they usually venture only short distances each day; fishing in the same spots and using regular perches. Until earlier this week AW had done exactly that. He has spent the past three-and-a-half months on the coast of Guinea, fishing in the sea and perching in the same area of mangroves just back from the shore. Then today, I downloaded the latest satellite data to find that suddenly he was 400 miles south-west in Liberia. I was absolutely amazed and even downloaded the data twice to make sure I hadn’t made a mistake!
AW's flight to Liberia, 17th-20th December

AW's flight to Liberia, 17th-20th December

So what is going on? Well, here is what we know from the current batch of data. At 10am on the morning of 17th December AW was perched on the beach in his usual area, probably eating a fish. An hour later he had moved eight kilometres inland. Bearing in mind how little he had moved around for the previous few months, this in itself was a notable change from the norm; but nothing compared to what happened next. At midday, he was 13 km to the east, heading south-east at 30kph. Perhaps he was seeing off another Osprey? That obviously wasn’t the case though because an hour later he was another 27km further on and still maintaining the same course. This was more like migration! And that’s what he continued to do for the rest of the afternoon. By 5pm he was close to Conakry, the capital of Guinea having flown another 160km at a remarkably consistent speed along the coast. At 6pm he was perched either on the ground or in mangroves beside what on Google Earth looks to be a complex river delta system just to the south of Conakry. He was probably eating a fish; and no doubt there were plenty of other Ospreys around. He then roosted in mangroves 4km further south.

AW at Conakry

AW at Conakry

 

By 7am next morning AW was another 22km south-east, again perched among mangroves beside a river. He was still there an hour later but he must have resumed his journey soon afterwards. Although we are missing a series of data points, by 6pm he had flown another 180km south-east, and was resting close to a river in central Sierra Leone! Sadly the satellite imagery for this part of Africa is poor, but he appeared to roost in an area of scattered vegetation a couple of kilometres to the south. What was interesting was that he was now over 100km inland. Since leaving his regular spot on the coast the previous morning, he had maintained an incredibly direct south-easterly heading. It appeared that he knew exactly where he was going.

Next morning AW left his roost just after 9am and flew purposefully south-east for the rest of the day at altitudes of between 500 and 1200 metres. He crossed into Liberia in mid-afternoon and by 6pm, when he finally settled down to roost for the night, he had covered 280km. During his last two hours of flight he had changed his course to a more easterly heading. Whether this was an intentional change of direction or influenced by the weather, we are not sure, but we do know that he roosted close to the town of Basanai in northern Liberia. Again the satellite coverage of this part of Africa is very poor, but it looks to be a fairly densely forested area at an altitude of around 350metres. It is certainly not the kind of place you would expect an experienced adult Osprey to hang around so the chances are that AW will have continued his journey the next morning. His radio is currently on a five day duty cycle meaning we probably won’t receive any more data until Christmas Day. It will be absolutely fascinating to see where he is by then. Aside from his slight change of direction during the afternoon of the 20th, he had maintained a consistent south-easterly course for three days, suggesting he is heading for the Sierra Leone coast.  Rest assured that we’ll update you as soon as the data comes in.

So what has prompted this sudden move? I rang Roy Dennis this afternoon and he was as stumped for an explanation as me. We have never recorded this kind of mid-winter movement by an adult Osprey before. It is possible, of course, that this is something that AW does every year. His southward migration was notable for a lack of stop-overs, but, in retrospect, perhaps that is all his time in Guinea was; an extended stop-over. Maybe his true wintering site lies elsewhere?

We haven’t yet updated Google Earth with this new data – but don’t worry, it will be done tomorrow morning.

 

An Easy Life

We’ve just updated the Google Earth tracking page. As you will see both AW and 09 are settled at their wintering sites in Guinea and Senegal. In fact the latest data really does demonstrate what an easy life adult Ospreys have in the winter. Both birds spend most of their time perched just inland, with one or two daily forays out to sea to fish. They usually catch within sight of land but on one notable occasion – on 19th November – AW was fishing six miles offshore. This reminded me of standing on the beach at Tanji in the The Gambia last winter and seeing numerous Ospreys fishing in the sea – and catching needle fish amongst others. Here’s a video we recorded that morning.

The migration facts

With 09 and AW both now settled on their wintering grounds, in Senegal and Guinea respectively, it has given us the opportunity to compare their flights to West Africa.

As you will know if you tracked their progress, the two birds followed a similar route as they flew south. Both birds crossed the English Channel at Dungeness and then flew south through central France, passing over Orleans and the Osprey nests situated close by.

As AW approached the Pyrenees he switched to a more south-westerly course to avoid the mountains, whereas 09 flew directly through the high peaks. Both birds then made good progress through Spain and, interestingly, we recorded the highest altitude for both birds on this section of their journey. 09 reached an altitude of 6112 feet as he migrated over Andalucia and AW flew south at an incredible 9055 feet just north of Madrid. Their flight paths then converged again in the south of Spain, with 09 crossing the Mediterranean at Tarifa and AW heading across the sea further east.

The migration routes of AW and 09

Once in Africa both birds skirted around the foreboding Atlas Mountains before following a remarkably similar route across the vast wilds of the Sahara. AW took just three days to cross the desert, with 09 taking a day longer. Each was clearly intent on crossing as quickly as possible; we recorded fastest speeds for both birds in Western Sahara – 29mph for AW and 50 mph for 09.

By the time he reached his wintering site on the Senegal coast 09 had covered 2972 miles from Rutland Water in 16 days – an average distance of 186 miles per day. AW flew further south to Guinea. He migrated 3277 miles in just 14 days – an average of 234 miles per days. Interestingly AW’s average speed was significantly slower than 09 – 15 mph compared to 29 mph – but by flying for longer each day, he completed his migration faster.   The table below summarises the key facts of the two flights.

  AW 09
Total distance flown 3277 miles 2972 miles
Duration 14 days 16 days
Average distance per day 234 miles 186 miles
Average speed 15 mph 27 mph
Fastest speed 29 mph 50 mph
Average altitude 2431 feet 1919 feet
Highest altitude 9055 feet 6112 feet

Finally, here is Osprey fact of the day. 09 is thirteen years old and now we know where he has spent each winter since his first migration from Rutland Water in 1998. This means that in his lifetime he has migrated a staggering  75,000 miles. In other words he has flown round the world three times!

09 and AW settled in their winter routine

09 and AW may be wintering 600km apart – on the coastlines of northern Senegal and Guinea respectively – but their daily routines are very similar. The satellite data suggests that both birds are fishing in the sea twice a day; usually mid-morning and then again in the early evening. Of the two, AW generally heads further out to sea -sometimes more than three miles – whereas 09 hasn’t ventured more then a mile from the coast.  Having watched Ospreys fishing in West Africa last winter, I imagine that it takes the birds very little time to catch their meal; probably just a matter of minutes. The remainder of their day is spent on their favourite perches. In AW’s case this is in mangroves 500m from the sea whilst 09 is usually perched among scattered trees just a couple of hundred metres from the breaking waves. All in all, being an adult Osprey at your established wintering site is a very easy life!

09's movements during the past ten days

 

AW's movements over the last ten days

If our experiences in West Africa are anything to go by, then the only other time that the birds will leave their perches, is to chase off other Ospreys. They will probably be fairly tolerant of the neighbouring adults birds – who they will recognise from previous winters – but less welcoming to newly arrived juveniles. We watched adults chasing juveniles numerous times last winter and this is one of the reasons that young birds wander about so much during their first winter in Africa. Here’s a video diary that we recorded in Gambia last winter. I suspect that the habitat at the winter homes of our two birds is very similar to that of Gunjur.

09 and AW settled at their winter homes

09’s latest data is in and it shows that, as we suspected, he has settled on the Senegal coast south of St Louis. So despite the fact that his territory in Rutland is just a few kilometres from AW’s, they are wintering 600km apart! Both birds have been making one or two short flights out to sea to fish each day before returning to their favourite perches just inland. Their routine is unlikely to change for the rest of the winter!

09 and AW's wintering sites in West Africa

I’ll provide a more comprehensive update of both birds’ recent movements next week, but in the meantime I’m off to run the Berlin marathon in order to raise money for our Gambia wildlife education project. Huge thanks to everyone who has sponsored me so far – through your generosity I’ve raised almost £3000. If you haven’t donated yet and would like to contribute to what we at Rutland Water feel is a very worthwhile cause, please check out my online fundarising page.