30th May and no egg

One male, two females and no eggs

For three days over the past week the osprey nest stood empty. Having at last found not one, but two females, we had hoped that one of them would have become the partner of SS and laid an egg. Perhaps this just isn’t going to happen now. FS2 – the blue ringed bird – returned briefly on Sunday while the other two ospreys were at the nest. SS now seems to be stuck with Mrs. O which doesn’t appear to be a match made in heaven.

Mrs O on a meal ticket

There is no interaction between them or subtleties of behaviour suggesting any kind of bonding or developing partnership. She squawks continually and demands to be fed which seems to be the chief reason that she is still hanging around. Mrs.O – the meal ticket osprey – demands fish, snatches it from SS’ talons once he lands on the nest and immediately turns away from him, dropping her wings in agitation and squawking continually. He doesn’t react, he merely wipes his beak on the sticks of the nest and moves away from her.

No more egg preparations

SS sole role appears to be to catch a fish, eat most of it himself and then fly onto the nest allowing Mrs. O to grab and devour the leftovers. So why does he bother to continue to feed her? There is no egg, he has stopped making scrapes in the nest and has stopped bringing in new nest material. She displays no affection towards him. Things seemed to have cooled down in terms of mating and there has been little further activity. Increased daylight in the spring, the fine weather, a new mate and hormones trigger sexual activity amongst ospreys; but there must reach a point over the summer months, if mating proves unsuccessful, when hormone levels fall and the birds lose their breeding condition.

Failed breeding attempt

The days are still long, having not reached the summer solstice yet, and the weather is ok, but no eggs have been produced from either female in this eyrie. This maybe suggests that the peak in hormones driving breeding condition in the osprey adults has waned. What we don’t know is what physiological conditions trigger the end to a breeding cycle when birds have not successfully laid eggs. We have had eggs laid in the past which have proved to be infertile and not hatched, but it is not clear as to why these particular birds have not produced an egg. Mating definitely took place between SS and both birds, so the lateness of the season might be the factor preventing successful egg production.

It will still be fascinating to watch the behaviour of the birds at the nest site to find out what they do from now on. SS will presumably continue to defend his territory and Mrs. O has no reason to leave if she is getting free fish. But will FS2 be back?

Territorial

When ospreys fail to breed they often build another nest close by. This is known as a frustration nest and is a spare home which may be useful to them in coming seasons should they choose to switch nest site. They would likely only do this if conditions became unfavourable at their original nest site. However, a frustration nest may encourage another osprey pair to take up occupation, encroaching on the territory of the first osprey. This may lead to a great expenditure of energy from the first osprey in defence of his nest site and territory. So it’s a risky strategy, but given that it takes such a long time for ospreys to build up a nest site, it may seem like a risk worth taking. The ospreys within Tweed Valley Osprey Project area have it easy; their nests were ready made nesting platforms created for them over the winter months by Forestry Commission staff.

No DIY needed

All our ospreys had to do was move in and fine tune their ready-made nests with new material. The main nest is a massive structure, having been continually added to since it was first created in 2002 and now looks entirely natural. However, it is wired together and secure so that it doesn’t blow out. Our rangers also remove excess material so that it doesn’t become too heavy over the winter. It saves SS quite a job when he returns, which is just as well, as he was so late arriving this season. His DIY skills have never been truly put to the test but his two-timing tardiness this season looks to have cost him dearly in having no family to raise.

Better luck next time

So the dear, philandering SS will need to arrive in good time next season if he is to be a successful dad again. He needs to actively find a suitable mate and ditch the fish-wifey Mrs.O. Sorry Mrs O but the constant squawking, fish grabbing and attitude to SS is not winning you any fans despite having been been cheated on.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s