Phew, what a week.

This time last week, Ceulan's (now) four-day data set came in. Apart from a quick trip around Lac de Guiers, Ceulan had settled in the area near the town of Rosso, on the Senegal RIver, since he arrived there on September 15th (he only left the Dyfi on September 3rd - still can't get over that!). On November 5th, however, he decided to move. There was nothing unduly concerning about this, first year ospreys do tend to move around more than adult birds as their environment changes around them.

What was concerning, however, was the fact that the last seven hours worth of data that came in were all coming from exactly the same spot. Unless they're roosting, it is highly unusual for an osprey to stay in the exact spot for seven hours and more, and this was from 10:00 to 17:00.

On November 5th, Ceulan set off up river heading east 

Then came the agonising wait until the next data download on Saturday.

Thanks to Paul and others on Facebook, we established that the spot that Ceulan had been perching on was an electricity pylon - and a huge one at that. Had Ceulan flown into it or been electrocuted?  Saturday's data would tell us one way or the other.

The huge pylon next to the Senegal River by the town of Dagana

Saturday's data came in very late, tea time. Our worst fears were realised - for four whole days Ceulan's tracker was indicating that it had not moved, all the GPS points were, more or less, in the same place. He was still in the same spot that he had been for those seven hours on November 6th, by the electricity pylon, only this time for four whole days.

Whenever we see this type of GPS point scatter pattern, it invariably means one thing

It looked as though Ceulan had died. What else could explain this type of data?

There were two things, however, that kept the door of hope just the slightest bit ajar. The first was that the activity readings coming from the tracker were indicating that it was moving normally (for every location point it sends out a random number which changes if the tracker has moved; generating the exact same number over a prolonged period means that it is not moving). 

The second, albeit faint ray of hope, was that Ceulan's tracker was indicating that he was in two distinct places (16.53233 -15.52533 and 16.53217 -15.5253), even though these were only 18m apart, well within the margin of error which could explain that there was only one location in reality. I couldn't stop thinking about this though - if Ceulan was alive, why would he by flying to and fro from one point to the next, just 18m apart?

Then, late on Saturday night, it dawned on me. Look at the photograph of the electricity pylon again - do those two prongs at the top look as if they might be 18m apart to you?

It still looked hopeless, however. If the GPS points were accurate and he was still alive, how was Ceulan fishing and eating? Yes, the GPS points only come in on the hour, but could Ceulan be setting off to fish, catching his prey, and returning to the exact same pylon all before the hand got back to 12 o' clock again?

Then on Sunday morning, another ray of hope. Because the data window opened late on Saturday, a few points are held back and are only sent just as the window closes (and you don't get notification as to when this is - you just keep pressing refresh until nothing happens any more or you fall asleep!). Three more points came in overnight - and these were nine miles away from the electricity pylon. Moreover, they were from November 8th, Thursday, between 10:00 and 12:00. Surely these could not be errors this far away from the other points?

Late point scoring - one to the north west 1.6 miles away, and three from nine miles away. Looking better.

The last of the three points at 12:00 was directly over water and had a speed reading - 8mph at an altitude of 30m. Perfect for a fishing osprey.

The utterly unthinkable was starting to look, well, thinkable again. If Ceulan was alive, and the tracker had been reporting accurate readings all along, what could explain Ceulan's sedentary behaviour for all this time? I started to look more closely at the actual location where the tracker was telling us where Ceulan was at.

Most of Ceulan's points come from the middle pylon in the image below. These pylons carry electricity from the Manantali hydro-electric plant across Mali and Senegal.

Electricity pylons, 400m apart on a west-east direction

Looking closely at the data, Ceulan seems to have roosted on one of these pylons (actually, it would be the next one along just to the right of the image) on November 5th and then, on November 6th at 07:00, 08:00, and 09:00, he was perching on the pylon on the right on the image. By mid morning, Ceulan had made it to the next pylon along - the one in the middle of the map, and this is where he stayed! You can see these on Google Earth.

During his time here the weather was very hot. In fact, the increasing temperature might explain his initial decision to move. Were the water channels where he was starting to dry up? Were people coming out to the fields en masse to harvest their rice crops and disturbing him? The data coming back from Ceulan's tracker was also indicating very high temperatures.

Rosso weather station - temperatures increasing to over 40°C by November 7th before returning to more 'normal' levels

Now the good news. Today's window has opened and enough points have come in so far to tell us one thing at least: Ceulan is alive and he's moving around.

It looks like he flew back from his favourite pylon sometime late on Sunday or early Monday (November 11th and 12th) to his original home range, 20 miles back down river just to the south of Rosso. He's been moving around this area Monday and Tuesday. The last point we have for him is the one highlighted on the map at 15:00 yesterday. He seems to be moving east, back up river! Has he been disturbed again?

I emphasise that the window has not closed yet on this data set. If there are any major deviances to the GPS points still to come in though, I will add an update later on. Suffice to say, for now at least, it is time to start breathing again.

I'd like to thank the many people who have written to me with their help and suggestions in an attempt to work out what Ceulan's tracker data might mean during the last seven days, particularly Tiger and Paul. What a fantastic way to decipher scientific data, people from around the world, literally, voicing their interpretation and applying their specialist expertise and finding an explanation to some baffling data. Citizen science at its best.

The tracker has not malfunctioned at all. Many of us are guilty, including me, of blaming scientific instruments when the data they provide does not fit into what we 'expect' to happen. We continue to learn from the tracker and, of course, from Ceulan. We are understanding more about osprey ecology and osprey migration each time we get data back, and long may it continue. And just like anything else in life and in science, the more we understand something, the better equipped we are to ultimately be able to fix problems related to that 'something'. And boy, do we still have huge problems with osprey persecution left.

It's been a tough old week. Nails bitten, hair even more grey, hours in front of the computer trying to work out what's happening. With scorching temperatures and some tough times ahead of him, Ceulan is not out of the woods by any means, but, for now at any rate, the news seems good.

Back from the dead? Well, probably not, but you do start to wonder, don't you, that this little bird has something just a little bit special about him?