Around the Atlas and into the Sahara

In the last update on 30’s migration, I suggested that when we received the next batch of data she’d be setting out across the Sahara. Sure enough, the latest GPS positions show that last night she roosted just north of the disputed Morocco-Western Sahara border, with the vast expanses of desert lying ahead.

We knew that at midday on 3rd September, 30 was passing to the north of Marrakesh. The imposing Atlas Mountains would have been appearing on the horizon, and this clearly prompted a shift in 30’s course. At 1pm, with the mountains looming large in the distance, she made a distinct turn to the South-west; thereby avoiding flying directly through the mountains. She maintained this heading for the next four hours at altitudes of more than 2000 metres. By 5pm she was past the highest of the peaks and she turned almost due south, a course she maintained for two more hours of flying. Finally, at 7pm she settled to roost in an agricultural area to the south of the mountains after a day’s flight of 293km. Here’s a Google Earth video of her day’s flight which demonstrates just why she changed direction as she did. If you like the song in the video, you can find out more about it here.

30's flight on 3rd September

30’s flight on 3rd September

30's roost site on 3rd September

30’s roost site on 3rd September

Next morning, 30 made a slow start. At 7am she had moved 5km south of her roost site and at 9am she was perched again, another 6km to the south. There are no obvious signs of water on Google Earth and it’s more likely that these small movements were as a result of people beginning their day’s work on the agricultural land. By 10am, though, she was migrating again, heading South at an altitude of 370 metres. She made steady progress for the rest of the day, maintaining a South-westerly heading at altitudes of 750-1000 metres. By 5pm she had covered 252km and at that point made another distinct turn in response to a geographical landmark. As our previous satellite-tracking studies have shown, many migrating Ospreys follow the vast ridge which runs South-west along the northern edge of the Sahara; and at 5pm that’s exactly what 30 did. She followed the ridge for two hours, before settling to roost on the desert floor at 7pm after a day’s flight of 324km.

The sight of the vast ridge in the Sahara prompted 30 to change direction and follow the line of the ridge

The sight of the vast ridge in the Sahara prompted 30 to change direction and follow the line of the ridge

Ridge in Sahara photo by John Wright

An aerial photo of the ridge, demonstrating why it is such an important landmark for migrating Ospreys

30’s isn’t the only Rutland Osprey to have followed the ridge. Both 09 and AW followed the same ridge on their migrations in 2011. Its also very close to the place where 09 sadly died on his autumn migration last year. at 5pm 30 was just 41km from the spot where Farid Lacroix found 09’s remains last September. Let’s hope 30 has better luck as she crosses the Sahara.

At one point, 30 was just 41km from where 09(98) sadly died on migration

At one point, 30 was just 41km from where 09(98) sadly died on migration

Like all Ospreys that are migrating across the desert, 30 had to roost on the desert floor. Google Earth helps gives us an insight into the kind of landscapes that she is experiencing.

30's roost site yesterday evening on the desert floor in the Sahara

30’s roost site yesterday evening on the desert floor in the Sahara

30's migration on 4th September

30’s migration on 4th September

With the majority of the Sahara ahead of her, 30 will have to go at least three more days without fish. For an experienced adult Osprey this is something she is well-used to, but it will be a difficult few days of migration nonetheless.

Don’t forget you can view all of 30’s migration data in your own version of Google Earth. Click here to learn how. Or to view in Google Maps, click here.

3 responses to “Around the Atlas and into the Sahara”

  1. Paul Syms

    This is phenomenal work. The $64000 question of course is … how is the migration route encoded in the DNA? Do different osprey populations have different migration routes hard-wired into their genes? If you were to cross an osprey from Rutland with one from Egypt, would the offspring lose the plot and try to overwinter in Skegness? Do we know if different populations around the world ever interbreed successfully? (Or are there barriers to interbreeding because the offspring will be poor navigators?)

    Oh, and couldn’t you make the maths puzzle a little harder …? 🙂

  2. cirrus

    I have my ‘eyes shut’ – the very mention of 09 and a tear sprang up
    Excellent Blog Tim but I just want 30 to have arrived safelly

  3. Rosie Shields

    Paul. I asked the same question on the Dyfi website and the answer was that there is no data supporting a correlation between related ospreys and migration routes. It was put nicely that the ospreys inherit a “How to navigate like an osprey” gene but nothing more. Hope that helps.