Blogger George asked a question about when the ospreys are likely to begin their migration? So I thought I'd answer his question with a wee blog and in so doing take this opportunity to begin to prepare you for their inevitable departure, as day by day we move inexorably towards that next stage in the lives of our birds.
The usual pattern, over all the years here at Loch Garten, is that female ospreys leave first. EJ could be gone by perhaps as early as c.8-10 August. Rothes, Mallachie and Garten are likely to be with us until c.20-24 August. Male ospreys are last to go, so Odin could be with us until he is confident that the youngsters have indeed gone, hanging on just that little bit longer for several days to check, then off he goes too at the end of August or early September. They do not go together as a family, though it is possible that they may encounter one another en route. Last year, Deshar and Nethy both spent a month or more in southern England, but not actually anywhere near each other.
One explanation why female ospreys go early, is that their job is done, the young ospreys are at least semi, if not totally independent by then, and the male is of course still around to provide back-up supplies of fish if the young still have not fully mastered fishing for themselves successfully. Also, because the female has; a) put a lot of her bodily resources into the production of eggs, b) been relatively inactive during the 36-42 days of incubation, and c) spent another two months hanging around the nest, guarding & tending the young - she is therefore relatively out of condition and potentially quite unfit compared to Odin. So she leaves early to give herself a longer time to make that migration flight, perhaps at a more leisurely pace, recovering her fitness along the way.
Odin, who as chief provider of fish, has spent months & months flying back and forth on fishing trips, anything up to 9 times a day, therefore he in contrast is as fit as a butcher's dog, as they say, is in tip-top condition and therefore can afford to delay his departure for the sake of the family, before he then heads off, when his fitness probably enables him to make good progress, and fast.
Interestingly, given EJ's resumption of fishing duites far earlier than we have seen from most female ospreys here at Loch Garten over the years - no doubt a result of learned behaviour, of not to trust males to provide enough fish, after her experiences with VS - it will mean that she will have regained some of her fitness, maybe returned to full fitness, and so be in a better condition to start her migration. Will that mean she stays longer? Or maybe she will just go early as usual, but be all the better to cope with the rigours of migration, arrive in West Africa in good shape, survive the winter more easily and return again to breed in 2010? Could our EJ have hit upon a strategy that will serve her well in future - start fishing early and get back in shape?