Recap – Failure of Second Egg

Like many things this season, the events surrounding the osprey nest at Loch of the Lowes have been complex and curious, including the loss of the second egg on the 8 June, which left staff and volunteers alike with more questions than answers.

Having been incubating well as a pair, female osprey LF25 suddenly and inexplicably began leaving the egg exposed, whilst her mate LM24 stopped his usual early morning and regular incubation stints throughout the day.

At the same time it looked like LF25 could perhaps sense something was happening within the egg, when she suddenly stood up and stared into the nest. A few days later, as the egg entered the early part of the hatching window, she again behaved as if she could sense something and began fussing with the egg, usually a sign a hatch is underway.

However, rather confusingly the egg was also being left exposed for longer and longer periods, including in wet weather. In the last two days of incubation the egg was left uncovered for 3.5 hrs and 5hrs 40 min respectively.

Since there was no human disturbance, fish supply was regular and there were no mammals such as red squirrel or pine marten observed climbing the tree* that might cause her to abandon, we can only assume she somehow knew the egg wasn’t viable….*(protection is in place to prevent mammals climbing the tree).

Perhaps her odd behaviour could be explained by hearing a small bird in the layers of nest below her? Maybe the egg had been damaged some weeks before and was never going to hatch? Usually osprey will incubate well beyond the hatching window before giving up. Or as a first time breeder, is it possible she could have been spooked by movement and sound within the egg?

The honest answer is we really don’t know, there is so much more going on than we can see or hear, and it is too easy to project theories onto events to suit a narrative.

Given how long the egg was being left exposed however, it was only a matter of time before a predator came in to take advantage, especially as there was no osprey on territory at all – again this was unusual since LF25 had rarely left the reserve for more than a short period since her arrival!

In this case it happened to be a crow that was opportunistic, however it could just as easily been another predator that chanced their luck.

Despite its best efforts, the crow was unable to either pick up, or break into the egg, and soon gave up having buried it deep into the edge of the nest.

On their return, both LM24 and LF25 attempted to ‘phantom incubate’, such is their drive and instinct, however by the end of the next day this behaviour had stopped.

Nesting Frustration

Despite the failure of the young osprey pair to hatch any eggs this season, they have been busying themselves with some further nest renovations.

It is common to see this behaviour continue throughout both a successful and failed breeding season. Some ospreys go a step further building what is known as a ‘frustration nest’ nearby after a failed attempt to hatch eggs or if they lose young at an early stage.

No doubt the practise of what type of material to bring in and where to place it will stand them in good stead should the young pair return next year.

Bonding Over Food

Young male osprey LM24 has proved himself to be a good fisherman, bringing in a steady supply of fish throughout the season so far. Although there will be no chicks to provide for this year, female osprey LF25 will still expect him to deliver fish to the nest. This will help strengthen their bond over the duration of the summer.

Brown trout has been the most popular fish so far this year, with rainbow trout, perch, pike and even the odd grayling also featuring.

LF25 is also doing a spot of fishing from time to time, when the ‘Fisheroo’ service is a little slower than she would like!

Defending Territory

Throughout the season every osprey pair will have to defend their nest and territory from unwanted intruders, who are keen to claim a prime spot of real estate, rather than go to the trouble of building their own! These are typically young, osprey still looking for a mate and/or a territory, although breeding osprey will ‘noise up the neighbours’ from time to time too!

Having managed to claim the site this season after a few other pairings tried to give it a go, LM24 and LF25 have been defending their territory well. More often than not all that is required is to stand firm, mantle and emit some loud ‘guard calls’ to put off the competition, although they will take to the skies to see off any stubborn unwanted attention.

‘Blue 210’
That said, at the time of writing it looks like female LF25 has gone off gallivanting and exploring for the day, as ospreys without young can be prone to doing throughout the season.

As a consequence the nest has attracted the attention of female osprey ‘Blue 210’, who had been seen intruding already this season and more recently on a nearby nest at Alyth. As a ringed bird we know that ‘Darden’ (as she was named) fledged from a nest in Kielder in 2020, and bred last season in the wider Perthshire area.

She certainly has been making herself at home, relaxing on the nest for 3.5 hours earlier in the day, enjoying a spot of lunch from LM24 and then returning again in the late afternoon to soak up the balmy evening sunshine for another 2.5 hours! The question is what will happen when LF25 returns to reassert herself on the nest? She was last seen early this morning, partaking in a spot of ‘breakfish’, so no doubt it won’t be long before she returns again….or does she have other ideas?

Assuming she returns from her day trip, we expect LM24 and LF25 to continue to strengthen their bond, until they leave for migration in the late summer/early autumn. All being well, should they return next season, when they will be able to build on their experiences to hopefully raise their very first chicks.

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