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Glesni Lays Her First Egg - 2016

Posted: Monday 18th April 2016 by Emyr MWT

Monty and Glesni with their 1st egg in 2016Monty and Glesni with their 1st egg in 2016


Glesni has laid her first egg of the 2016 season. At 04:07 this morning, 18th April 2016, this happened:



Glesni laid her egg exactly 16 hours after her cousin, Blue 24, laid her first egg on Nest 2 on Cors Dyfi reserve. The nests are around 300m apart.

 Glesni's first egg of the season and 8th in all.


It has been an interesting day to say the least. These kind of polygamous situations are relatively un-recorded in the literature. I have been talking to my colleague Tim Mackrill at Rutland Water today - they had a similar situation at their Site K in 2014 and also to Vanessa in Minnesota, USA, who has also experienced polygyny (one male, two females) in ospreys at their Twin Cities Metro nests.


 Love Triangle: Glesni-Monty-Blue24


With all the recording we do of our ospreys at the Dyfi, we have an almost unique and unprecedented opportunity to better understand these kind of osprey reproductive systems in ospreys this year. One common behaviour of a polygamous male osprey is a tendency to favour one nest over another. A kind of primary and secondary nest preference.

To try and capture these preferences, if indeed they exist at all with Monty, we will concentrate on and study two main behavioural aspects - incubation times by Monty at both nests and food sharing. Paternally, does he tend to invest more at one nest than the other? We aim to find out.


 Monty carries a half eaten sea trout between nests this afternoon - he made sure that both females ate.


Those of you that watch the Live Streaming can help. If Monty incubates Glesni's egg(s) say between 21:23 and 21:55 - let us know either on Chat or on Facebook. Don't worry that we might get several accounts of the same incubation times; better we have 17 records of the same event than none. Meantime we'll keep an eye on Nest 2 and the number of fish he brings in - we can then compare these to previous years to see if the amount of fish he catches has increased, and if so, by how much.

We will also record the first location Monty takes his fish to - Nest 1, Nest 2 or somewhere else. By recording this information over many days/weeks, we will get a better picture if Monty has indeed formed a nest preference system or whether he is trying to be as equitable as possible.

Monty has been pretty unbiased today. He's caught four fish and has made sure that three ospreys have had enough to eat: himself, Glesni and Blue 24. He's also shared incubation duties at both nests and has mated both females. Interestingly, we have only recorded him bringing nesting material back to one nest - Glesni's nest.

Look out for a blog on polygamy in ospreys later this week, interesting times ahead...


Taken from the 360 Observatory this afternoon - Monty has his share of the trout on the lower perch after both Glesni and Blue 24 have had their share.


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