Posted: Wednesday 1st July 2020 by Emyr MWT

We ringed our two chicks yesterday, 30th June. We have two boys.

We've had an all-female clutch once before, Cerist and Clarach back in 2013, but this is the first time we've had an all-male brood.

Both chicks were weighed and had buccal (saliva) swabs taken; we've named them Tywi and Teifi - both south-west Wales rivers.


Both Tywi and Teifi were ringed a day or two earlier than average in order for us to fit them into a weather window - there's a lot of rain and high winds around this week. Thankfully it was relatively calm and quiet yesterday afternoon.

Here's the updated winglength chart with Tywi and Teifi's measurements included:

And the chick weights at ringing - note the very clear differences between males and females:

We retrieved the unhatched egg, it was still intact. Under license we will now display the egg in the Dyfi Wildlife Centre next year onwards for educational purposes.

The egg (Egg 1) had faded markings by now and felt heavy as we expected. It is almost certainly fertilised but failed to hatch due to prenatal failure, meaning that chick development was arrested - probably very early on.

Egg 1 was removed from the nest

With no Posh Pete Test possible this year due to the lockdown, here's how we decided on the two names.... Many thanks for the suggestions on the Facebook post over the weekend, what great fun.

On The Ground

Very often once we bring the chicks down to be ringed there is an obvious and tangible difference in size, a measure that is impossible to perceive looking at the nest cameras. This year there wasn't. In fact, there was only a 40g weight difference between both birds, the oldest by two days, Tywi, having the weight advantage.

There was a very obvious difference in appearance, however. Teifi, the youngest, was a heck of a lot paler than his older brother, and not just with head plumage. Looking at both birds side by side, it was clear to see Tywi was several shades darker than his kid brother.

Teifi (closest) is a lot paler than his older brother Tywi

Tywi with his darker head

Tywi and Teifi were also polar opposites in their behaviour. The younger Teifi was one of the most placid osprey chicks I've ever seen, he just lay there watching us go about our work. Tywi, however, was not so serene. He was pecking so much at Tony, we almost called him Gregory.

Thank you as always to Tony Cross and his daughter, Amy, for ringing our birds with the usual level of professionalism and enthusiasm.

Amy helps Tony position his GoPro camera

Thanks also to Ilze for helping out. Once the labs open up again at the end of the summer Ilze will get to work on the swabs we took.

Here's the 2020 DOP Ringing Video:

Read Emyr MWT's latest blog entries.