This is the blog I hoped I would not have to write, not for many more years anyway. We have lost contact with Dulas.

The last blog, written on June 6th, was a celebration of his first year and all the trials and tribulations he had been through in just twelve months. Six weeks later, on July 13th, we received the last transmissions from his tracker. At this time of year he's on a three day cycle, so we should have received more data on the 16th, 19th, 22nd and so on; we haven't.

Looking closely at his last set of data, everything looks normal up to the the last few hours. On July 13th, the activity reading doesn't move from 09:55 until his last data point at 15:33, meaning the tracker didn't move during this time. We have had no transmissions since then.

The yellow bird denotes Dulas' last position at 15:33 on July 13th, 2012

Dulas has been in this part of Guinea Bissau for the best part of six months - you can see when he arrived here by the white data bubble on the map above. He's spent most of the time near the mouth of the river with the occasional trip further up stream - something that we really didn't like to see him doing. Why?

One of Roy Dennis' ospreys, Spey, tagged in 2010, made it all the way to Africa and then, at just over a year old, disappeared. Spey's similarity to Dulas is uncanny: both male, both left the UK and eventually made it to this part of Guinea Bissau by their first birthday. Then, suddenly, the trackers stop sending signals. Incredibly, Spey and Dulas' last positions are just three miles apart on the same river. Coincidence?

Just three miles separate Dulas and Spey's last data transmissions almost at exactly the same time of year

We all know the stats. Only around 30% of young ospreys that leave the UK ever make it back in two or three years time, osprey mortality for young birds is high. Satellite tracking research is answering a lot of questions that ecologists have been pondering for years - I think it's true to say that we all thought that a decisive factor in explaining this low return rate was the long migrations that ospreys take, the first one, of course, for the very first time. It is starting to appear that this is not the case. The vast majority of first year birds are arriving in Africa safe and well and then surviving many months, sometime longer.

So, what could have happened to Dulas?

1. Natural Causes. We are beginning to learn now that being a young osprey in Africa is tough. Competition from other ospreys, birds, is intense. But now with all the adult birds back in Europe breeding (or attempting to breed), you would think that competition from other ospreys would be negligible. Perhaps he has been predated, maybe he had a disease, maybe he had an accident whilst flying and/or fishing?

2. Human Causes. Guinea Bissau is a desperately poor country, people live on what they can catch and grow in the wild. Yes, people eat birds, yes, people eat ospreys. It's a sobering thought, but Dulas may have been eaten. He could also have been trapped in fishing nets or line - this is a problem ospreys face the world over including in this country where many osprey die each year after getting tangled up.

3. He's still alive. Let's end with the positive option. I have spoken to Roy and Tim at Rutand over the last couple of days, they have been kind enough to look at Dulas' data for us. Many thanks. Just like any technology, it can break. Maybe the tracker on Dulas' back is still there but not working; maybe it has fallen off and ended up upside-down, unable to send any more transmissions. Both Roy and Tim say this is a possibility, albeit remote.

At the end of the day, we simply don't know. We are all here at Montgomeryshire Wildlife Trust, staff and volunteers alike, hoping for the best, of course. I suppose that if anybody were to spot Dulas return next May or June, we have a good chance here at the Dyfi with all the High Definition cameras and optics we have. Being purely objective, however, and saying this with a heavy heart, the probability is that Dulas has become one of the 70% of ospreys that never make it back to the UK. Dulas was a year and 37 days old when we lost contact; absolutely gutted.

The last image of Dulas on the Dyfi in September, 2011 - the following morning he started his migraton to west Africa