Roy's Migration Blog:
This proved to be the start day of an incredible non-stop migration. Nimrod was at his usual roost until 8am but was over Etang de Bicarrosse by 2pm and near Lit-et-Mixe. At 4pm, he had changed heading to the south to fly round the west end of the Pyrenees, and was flying SSW at 56km/h at 166metres inland of Hossegor. At 5pm he was flying at 54km/h SW just south of Ustaritz and then flew over the border into Spain.
His day's journey to this point was 462 km.
Nimrod has flown over the whole of Spain by moonlight.
The first fix of the day (the transmitter's GPS is off from 8pm - 6am GMT) showed he had flown at least 782 km overnight and was 113 km from the Andalucian coast flying at 18km/h SW over the Atlantic Ocean towards Morocco. During the night it appears his SW heading took him over Madrid and he crossed the coast at Mazagon at about 4am.
It was perfect conditions for a night flight with clear skies and a
nearly full moon, but intentional night flights over land by Ospreys are
very unusual. He covered 782 km in the 10 hour flight, which is a mean
speed of 78kms/h, which meant he had picked up favourable tailwinds. He
clearly knew his route and high over Andalucia he would have seen the
Atlas Mountains of Morocco.
It is interesting that he then set off SW to Morocco for a 690 km flight over the Atlantic Ocean to the west coast of Morocco at Essaouira, which meant that he avoided flying over the series of high mountains in Morocco. Over the ocean, he was flying between 58 and 483 m above the sea at speeds between 56 and 90 km/h. His route was direct and he came ashore at Essaouira at 2pm, he had passed Agadir by 4pm and then flew down the coast, before heading south into the deserts and finally came to roost near Leimadrat in South Morocco.
This was an incredible 2300 km migration flight, non-stop in about 35 hours, at an average speed of 68 kilometres per hour. He had obviously decided that it was time to get to Africa and his winter quarters after his 12 day stop-over on the French coast. After this flight, Nimrod "the mighty hunter" could also be called the mighty navigator!
At 7am, he set off over the desert, stopped an hour later, and then set off strongly on a SSW migration, he passed into Northern Mauritania at 11am, and during this three hour period was flying at 80 to 85km/h SSW at 800 to 900 m altitude. At 2pm, he crossed the border into Western Sahara at 1329 m, and at 5pm was back in Mauritania flying at 43km/h SSE at 1235 m and 2 hours later settled for his night roost in open deserts in Western Sahara, about 40 km west of the huge iron ore mine at Fderik.
Today's migration was all over hostile open deserts, stony plains and rocky mountains ridges. The day's flight was 567 km.
Nimrod restarted his migration at 9am and for the next three hours flew SW at 53 to 72 km/h over the Sahara Desert. When this batch of signals ceased at 10am, he was 300 km from the Atlantic Ocean coast of Mauritania at Arguin.
Nimrod continued his flight down through the Sahara Desert and into northern Mauritania, and yesterday morning appeared to be heading directly towards the Atlantic coast, where he could catch his first fish since leaving the French coast. But he surprised me again by changing course to the south and keeping well inland from the coast, and by late afternoon was to the west of the capital Nouakchott and appeared to be heading for Senegal.
I find it really fascinating trying to understand the changes he makes along his migration route. I also find it nice to think that even with our fantastic technology and knowledge, which allows us to track his movements and correlate them with geography, weather, ecology and the seasons, we will never know what he (or any other migrating bird) is actually thinking. It was probably his fit condition and a change in weather that stimulated his departure from Ile d'Oleron - but had he already decided to fly non-stop to Morocco before he set off?
Did he decide to fly through the night, because the moon was bright, or because he just wanted to get quickly to Africa? And then why did he turn south, 30 kilometres or so from the Mauritanian coast, where he could fish, and instead head on south over the deserts and delay eating for another day or more?
Nimrod moved from his roost after 7am, and at 8am was perched in the desert 19 kilometres to the south. Just after 3pm, Nimrod crossed the Saloum River (a favourite wintering area for many ospreys) and at 5pm he had crossed into The Gambia, where at 6pm he was perched in the swamps on the south side of the main river north of Bwiam, he then flew 3 kilometres west to a roost beside a small tributary of the river, near Dambutto. His day's flight was 400 kilometres. I wonder if this might be his wintering area - it's certainly good for fish.
Roy Dennis' Nimrod Migration Blog