UV returned to his wintering grounds in northern Senegal just over a couple of weeks ago. He has been to many familiar places. Here is an overview of his activity.
Not just sitting on the beach!
The range shown in the image is 510 sq km. If the excursion east and north on 19 October is removed UV is travelling around 140 sq km of land and sea with an ‘average’ day encompassing roughly 100 sq km. Many overwintering ospreys have a range under 10% of that – for example the Loch of the Lowes 2015 male FR3 has spent most of his time in an area of about 5.5 sq km although he does venture further afield.
Since his return UV has occupied perches mainly on the north spit of the Langue de Barbarie and an inland area near Lac Guembeul. He has roosted in several different habitats including within the National Park on the south spit of the Langue de Barbarie – a rare occurrence since he more or less abandoned that territory in autumn 2015. On 23 October he roosted in the same trees he used many times from April to October last year. But there are no daytime fixes of UV in the National Park.
One of the interesting aspects of UV’s behaviour is his foraging, but first we’ll examine that excursion. UV flew east then north at altitudes of over 400m ASL, much higher than normal when in wintering grounds.
High flyer UV
UV’s high flying ceased at the Ngalam river which he has explored before.
He flew on without stopping and headed for the north spit of the Langue de Barbarie. He reached over 500m ASL. Most of his flying in his first two of three journeys over the sea was too high for foraging.
Here is a NASA satellite weather image.
courtesy Paul Wildlifewriter
The wind direction in weather websites was N or NE so why was there dust from the Sahara in the atmosphere? Paul explains:-
“Ordinary” weather maps are useful, but they don’t always tell the whole story. On the 19th October, ground-level winds followed the usual pattern of onshore sea breezes during the afternoon. But in the layers of atmosphere between 1500 and 3000 m, the winds were blowing in the OPPOSITE direction, carrying high-altitude dust from the desert interior.
UV’s high flying to the Ngalam river and back was probably unrelated to dust above him but that, coupled with silty water below (inset in the weather image), might have made it even harder to forage off north spit. He could have been looking for better conditions further afield. Frequently since his return to Senegal UV’s foraging has been some distance offshore with many flights between 2.5 and 5 km from land. Paul has made an animation which shows this clearly.
This graphic shows where there will be plentiful fish supplies.
courtesy Paul Wildlifewriter
UV isn’t fishing in the river at all because although the seasonal rains are now over sediment is still being carried downriver (the inset in the NASA image above). Observer on the ground and friend of Kielder Ospreys Jean-marie Dupart writes a blog about wildlife in northern Senegal and on 26 October described the ospreys foraging at sea, not in the murky river. If you read Jean-marie’s post you’ll see he had over 50 osprey sightings albeit as he says some could be the same bird twice. A great place to visit!
Last autumn UV changed his foraging areas from ‘close to shore’ to further afield, reinforcing the view that fish migration and the clarity of the water are the reasons for alterations in behaviour. Fishing in the mostly clear and quite shallow rivers of northern England must seem a long time ago to young UV!