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Welsh Osprey Round-up

Posted: Sunday 10th May 2020 by Emyr MWT

Quick Welsh Update as of 10th May 2020

We have five osprey nests again in Wales:


Telyn and Idris (new male), Monty did not return. Three eggs, due to hatch 23rd May onwards (more likely 26th though).

Telyn laid her three eggs at eggsactly the same dates as last year, despite having a new male



Mrs. G and Aran, both resident birds. Three eggs, due to hatch 19th May onwards.

Three Glaslyn eggs in 2020                     ©BGGW


Llyn Brenig

Blue 24 and Blue HR7 (Scottish), both resident birds. Incubating eggs, due to hatch 20th May onwards.


Llyn Clywedog

Dylan and Seren (formerly Blue 5F, renamed by local schoolchildren). Resident female, Delyth, did not return. Three eggs, due to hatch 23rd May onwards.

Seren and her clutch of three eggs at Llyn Clywedog                © Natural Resources Wales 

Snowdonia ON4 Nest

Resident unringed female with new male, blue ring, right leg. Previous unringed male did not return. Incubating eggs, hatching window similar to above nests.


So we have a minimum of 11 eggs, and a potential (realistic) maximum of 15. The most amount of chicks we've had in the Welsh population reach migration age in one season is 11 (both 2018 and 2019).

Let's hope we can get to at least 12 in 2020 - that would be a new record.

Currently all bird ringing is prohibited in the UK outside of a ringer's garden; we're hoping, however, that by the time the Welsh chicks get to five weeks old at the end of June/early July, these restrictions will have been lifted.

We have a 2020 licence to buccal Swab (DNA) the Welsh chicks again this year.


So, a couple of things worth noting here:

1. Three resident birds, Monty, Delyth and the ON4 male failed to return in 2020. That's a pretty shocking statistic.

On average, approx 92% of established breeding adult ospreys return each year. In Wales in 2020, only seven out of 10 returned: 70%.

Delyth (top) bred at Clywedog from 2014 - 2019 raising 15 chicks to migration age. She did not return in 2020. ©John Williams

2. Despite this 30% loss of breeding and experienced birds, new ospreys came in and replaced them extremely quickly. In fact, all five nests are due to hatch within a week of each other - and all at around conventional times: third and fourth weeks in May.

This is a function - and resulting advantage of - having a recovering population in Wales. Our small colony here is not exposed to the usual ecological dynamics and pressures of a more stable, normalised and saturated population, like those you would see in many parts of Scotland.

Graph: This is what a recovering osprey population looks like once it reaches maturity. Saturation (the plateauing off of the curve) is reached when one or more limiting factors are reached; these could be food availability, ecological density, predation pressures, available nesting sites (although not in this case - population levels off despite more platforms being erected for them) etc.

A mature osprey population in Martha's Vineyard, a Massachusetts island, USA, reaches saturation and 'normalised' status despite more platforms being erected


The competition for nest sites and mates in Wales is a lot lower. For that, at least for now, we can be thankful.



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