Thursday, 15 April 2010

Exciting times!

Another beautiful day at the hide - what a week it has been! With clear blue skies and thermals rising, Skye and Frisa have been giving us some fantastic displays. On Tuesday Frisa drifted over the top of the hide, caught a thermal and spiralled up and up until she was no more than a dot in the sky, with never a wing beat. It must have been wonderful for her to stretch her wings after a long spell on the nest.

Talking of the nest, we are all on tenterhooks as we wait for the egg(s) to hatch. Today is day 36 of an average 38 days of incubation and the birds have been quite fidgety on the nest, which is a possible sign that a chick is getting ready to hatch. It can take 36 hours from the time the egg first pips to the time the chick hatches, but even before it pips the adult birds can hear the chick calling inside the egg and will sometimes call softly back to it to encourage it to start to break out. The chick develops with an "egg tooth" - a tiny sharp bit on the top of the beak which it uses to tap away at the shell from inside until it breaks. It then works its way right round the egg until the top falls off and it can struggle out - damp and bedraggled and small enough to fit into a human hand. It's tiring work, but the adult bird will keep encouraging it with gentle calls.

The chick hatches with the remains of the "yolk sac" inside it and spends up to the first 12 hours of its life outside the egg absorbing the sac and all the goodness within it. Then it will start to call for food and that's when the adults' hard work really starts. To begin with one adult will continue to brood the chick (and the remaining egg if there were two), whilst the other hunts and brings food back to the nest. Then the adult will stand over the chick with its talons bent underneath its feet to avoid standing on the chick, and will tear tiny strips of food from the prey with its beak which it offers to the gaping chick. It is the most amazing thing to see - such an enormous bird caring so tenderly for its young. By day four the chick's egg tooth will have disappeared, it will have dried out and be covered in pale grey down. The adults will continue to brood the chick(s) for two to three weeks while their adult body feathers are coming through and they are less susceptible to the cold, but if the weather turns cold and wet the adult birds will make sure that the chicks are kept warm.

Both adults hunt to feed the chicks, taking turns at feeding, brooding or just perching close by "on guard". By the time the chicks are ringed at around eight weeks old they are fully grown and spend the last three or four weeks in the nest growing down their flight feathers and practising wing flapping exercises ready for their first flight. It is an incredible growth rate. As with most birds of prey, female sea eagles are larger than the males, and it was strange to see last year's female chick, Heather, perched next to her father and looking down on him when she was only three months old.

As yet we don't know whether we have one or two eggs, so we will be watching with bated breath over the next few days to see how many little heads pop up in the nest. As the eggs are laid two or more days apart, there is an equivalent gap in their hatching, so we probably won't know until this time next week how many chicks we have. Watch this space!

If you read my last blog about Operation Easter, I can give you an update on our oldest pair of sea eagles on the island. Their first chick hatched on Monday, so we are waiting now to see whether they are feeding one or two chicks. It really is amazing to see how this pair keep going - last weekend there was a major grass fire just half a mile from where they are nesting, yet despite the activity with three fire engines and their crews working hard to put out the fire, the birds kept calm and stayed put. I've been privileged enough to watch this pair for over 10 years now, so have become very attached to them.

Fingers crossed for Skye and Frisa and their offspring - I'll keep you informed.

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