UV arrived back in his wintering area on 15 October 2017. As in 2016, he had several exploratory flights further afield in the first few days after his return. Since then, he has been within his usual broad range. You can see the extent of it in Paul’s animation of UV’s flying fixes.
On many days UV travels well outside his core area of about 28 km². His furthest excursions are NE, to wetlands south of the Ngalam river (c14 km from the coast) and an irrigation canal running south from it (c11.5 km). Why does he visit these places? We wish we could give a definitive answer!
The reason is not weather related. Perhaps on some visits UV bathes in the fresh water, but there are fresh water lagoons in/near his core zone. Often, UV doesn’t stop, but overflies the area(s) then heads back to the coast. He sometimes flies high – over 500m ASL – either on the way there or back, occasionally in both directions. But in the wetland/canal region, he is usually recorded at altitudes of under 100m ASL.
The limited amount of information available from satellite tracked ospreys suggests UV roams more than most overwintering ospreys. One osprey who overwinters about 60 km south of UV, Rutland Osprey Project‘s 30(05), has a very small area, as you can see if you click on her name to open the link. She is a 12 year old female, but males can also spend virtually all their time within a few km². FR3, a 2015 male from Loch of the Lowes, is one such osprey, although as mentioned in his link, he had taken occasional jaunts. (His GPS transmitter ceased sending data this summer, but twice recently he has been seen in the centre of his wintering grounds.)
In contrast, an adult male who travels 16 km most days from roost to foraging grounds is Blue JV3/Jules, fitted with a GSM/GPS transmitter by the Roy Dennis Highland Foundation in 2017. There is so much still to learn about ospreys’ behaviour.
Close to UV’s core area, his data reveals interesting activity. Referring back to the animation, the land immediately north of the core – the northern part of the Langue de Barbarie – was a destination of choice in winter 2015-16, less so winter 2016-17 as agricultural activity increased there. The animation shows several visits to North spit from October to 2 December 2017 – then none to 1 January 2018. Jean-Marie Dupart told us that there was more fishing activity in early December – fishermen set up temporary camps and head out to sea in their pirogues, often leaving some people on the beach. UV spent over 3.5 hours on North spit on 2 January, so there can have been minimal human activity that day.
The Google Earth image is from April 2017. The first perching point is no longer on a sandbank off a short ‘finger’, as this photo taken from 35,000 ft in December 2017 shows.
That ‘finger’ is more than double the length now.
Finally, we haven’t received any data from 7L/Aln since 25 December. As we’ve said, cell towers are only present in the very south of the Banc d’Arguin National Park, and Aln is in the far north. She hasn’t had an incentive to travel any distance in recent days, as this graphic shows.
The concentrations just south of Aln’s area of Mauritania were particularly dense on 1 January. In Senegal, there have been several health alerts in the past three weeks or so about poor air quality, as usually happens at this time of year. Perhaps as the Harmattan season draws to a close, Aln will explore further afield again.