Our ospreys have now incubated their unsuccessful eggs for a staggering 74days to no avail. This shows just shows how remarkably persistent and dedicated they are as parents and just how strong the instinct to incubate is in birds such as these.
Many people have been asking why they haven’t give up incubating yet: The answer is that the birds don’t have an access to an accurate calendar, so they will continue until any possibility of hatching has passed, possibly when day length has changed so much they can tell it is obviously too late. There is also the possibility that they now know the eggs won’t hatch, but don’t know what else to do with them- the instinct to nurture is so strong.
I have also been asked a lot why they birds don’t know the eggs are infertile? Unless the eggs are badly damaged , they won’t smell rotten even if they are a bit addled inside. Both adult birds have been listening to the eggs , and by now must be aware that there is no chick noises from inside.
It is clear over the last 2-3 days that our birds behaviour is changing and they are finally beginning to loose interest. For the first time the female hasn’t incubated overnight every night as normal, and yesterday she sat almost the whole day on another nearby tree, not on the eggs.
Therefore we have decided it is now the right time to intervene and remove the eggs for scientific analysis, before they are further damaged or stolen by crows etc. This will hopefully give us some clues as to why the eggs haven’t hatched.
So if you see our professional climber Sam on the nest camera today, please don’t panic- he’s operating under license and will be as quick and careful as he can to minimise any disturbance to the adult birds. Every year our female osprey has a climber at her nest to ring her chicks and is usually remarkably tolerant, circling overhead and calling but not being overly aggressive, so we would expect her reaction to be the same.
Thanks to our SWT climber Sam ( to whom we owe a big thanks!) the unhatched eggs have been safely removed today from the nest. The birds were remarkably unfazed by the intervention and though the both circled overheard for a while there was remarkably little alarm calling and certainly no aggression. This is in marked contrast to the females usual constant alarm calls when we usually approach her nest to ring chicks.
The eggs themselves have both been found to be intact- no signs of cracks or holes in them or damage that would have been sustained in the crow attack earlier in the season.
We will now be taking the eggs to the National Museum of Scotland’s Ornithological Curator for further analysis to see if we can get any answers to why they haven’t hatched.