It is true that ospreys are faithful to their nest, and this nest loyalty in turn leads to the same pair occupying their nest or nests year after year, until one partner dies and is replaced by a new partner. But this is only a general, basic rule, it's not written in stone for all eternity.Janne+Ais wrote:For me it is interesting. One can read, that ospreys are not faithful to their partners but to their nest. Madis and Piret disprove this theory.
Some ospreys, but far from all, do have a second nest. These second nests again, are sometimes merely a heap of sticks, not even big enough to raise a clutch of chicks in, and sometimes they develop into real nests.
One reason why they sometimes build a second nest could be that when fishing is good for the male, and he can easily provide for his family, he has time left on his hands (or rather talons). Another reason why this sometimes happens, is when a pair of ospreys are early breeders in the season. By the time their chicks have fledged, it's still too early to migrate, and the adults are still in breeding mode, so they (mostly the male) keep collecting sticks. The third reason is that they often build an second nest when a breeding attempt fails, and it's still too early to migrate etc. Such a nest is then called a "frustration nest".
Last year Piret and Madis' breeding attempt failed, after all the hassle with Oxana, and the fights between Piret and Oxana which followed. When Piret finally reclaimed her nest and Oxana was driven off, it was already too late to breed, and after a week or so they only visited the nest sporadically. Therefore it is not unlikely that Piret and Madis did build a second or frustation nest last year (or extended an already existing second nest), and that they this year decided to breed there.
When Madis arrived this spring, he began with restorations on the old nest, but when Piret also arrived, these 'nestorations' stopped within a few days. This makes me believe that Piret, as the female she is, chose the other nest to breed in (in many species -often including the human species - it's the female who has the last word when a nesting site is picked; the male only presents possible nesting sites).
And when you are a male osprey called Monty, there's a fourth reason to build a second nest...:
Sometimes we hear people talk about ospreys building 'frustration nests'. These are birds starting to build an additional nest close to their primary nest. But why?
Frustration nests are usually associated with birds that have failed to breed in a particular year or birds that have finished breeding early. The Glaslyn male osprey is a classic example of this type of behaviour.
Because both Glaslyn ospreys return to breed so early in the year (they usually have chicks by mid May!) they also, therefore, finish earlier. However, their biological clocks tell then that it's not time to return to Africa (or southern Europe, we don't know) yet. Problem is, the birds are still in 'breeding mode' in late July and August despite their offspring having fledged the nest weeks previously.
So a convenient interpretation for birds building supplementary 'frustration' nests (only a few sticks though usually) is this pent up urge the birds have do breed because they are still at their breeding site and breeding time of year. A classic 'displacement behaviour' where an animal's basic drive (in this case to breed) is frustrated owing to the fact that the chicks are well and truly grown up!
So with all that cleared up then, what on earth is Monty doing here in mid/end of July..
He's not failed to breed, he's not early (in fact, he's very late) and the chicks are only four and a bit weeks old. This camera pole was here last year and we saw no such behaviour then, but since around July 20th this year Monty has started to build himself a second nest - just feet away from his main nest.
How very, very bizarre!
Just when we think we're starting to understand these wonderful birds, they go and prove how utterly naive we all are. How very humbling. Please do suggest an explanation if you have one in the comments below of what Monty is up to, because I have absolutely no idea!
UPDATE: August 4th.
We asked Roy Dennis what he thought Monty was doing, here's his response. Thanks Roy.
Some males do a lot of building as the chicks grow in the nest - it makes the nest flat and also more secure for the following year, but it is rare that nests have an obvious extra base just above them. The camera array top encourages the male to have the new nest at the most prominent place rather than down below the structure. He would prefer to use the highest site as it will have 360 degree vis and approach, if it was still there next spring he would use it.
This is what Monty's new nest looks like now, August 4th!!
http://www.dyfiospreyproject.com/blog/2 ... frustrated