Thursday, 13 June 2013

Golden Eagle prey
Some of the prey items below the eagle eyrie
Whenever we visit a Golden Eagle eyrie, we always search around below the nest for pieces of prey dropped from the nest, and whoever climbs to the nest also has a good rummage through the nest lining for any more pieces.

Yesterday, while at the eyrie described in the previous post, we found remains of a Red Deer calf, a Roe Deer calf, a hen Rock Ptarmigan, a Red Grouse and what seemed to be feathers from a Common Gull in a pellet.

Both the deer were new-born calves, distinguishable by the unbroken cuticles on the soles of their hooves as seen in the photograph below.

The hoof of a Red Deer calf on the left, and a Roe Deer calf on the right. Very similar, but that of the Roe is smaller. A Golden Eagle can easily lift a Roe Deer calf, although a Red Deer calf must be a bit heavy to carry very far. Hence, both calves had been dismembered before they were carried to the chick in the eyrie, which might have been several kilometres from the place they were found.

Ringing a Golden Eagle chick
A four-week old Golden Eagle chick with a wonderful view from its eyrie. What an entrance to the world.
Yesterday I was up helping members of the Highland Raptor Study Group ring a Golden Eagle chick in an eyrie which I found a few days before. The eyrie was in an old Scots Pine, set about twelve metres up on the main stem where the branches split into a multi-fork. This presented a bit of difficulty in climbing up to the nest, but Brian Etheridge rose to the challenge.

Brian negotiates a route up over the eyrie
The eyrie was about two metres deep and two metres wide
Adam with the chick, a strong, well-fed male. 
For safety, the chick was lowered from the tree in a bag and ringed on the ground. Adam Ritchie ringed it as he had only done a a couple before, and putting on the extra-strong rings takes a bit of practice. The chick was a strong, healthy male, readily sexed by his relatively small feet and quiet nature. Females are larger with big strong legs and feet, and they are usually much more aggressive.

Sunday, 2 June 2013

Tracking Greenshanks
A colour-ringed and geolocator-tagged Greenshank
This year, 2013, we (Me, Nick Christian, Brian Etheridge and Ron Summers) caught several Greenshank and marked them with individual colour ring combinations. The orange ring on each also held a tiny, less than 1 gram, geolocator. The Greenshank weighed about 200 gm. This is a device which can determine the birds' approximate location to within 100 km, by analysing the relative daylight length with Greenwich Mean Time. The information on where they have been is stored in the device's memory and downloaded on subsequent recapture of the birds.

We retrieved two geolocators which had been put on birds last year. And the preliminary results suggest that Greenshank which breed in northern Scotland over-winter in southern England, Wales and Ireland.

Golden Eagle hatching
A Golden eagle eyrie set on a cliff
While out on a moor watching Greenshanks, in the northern Highlands, I noticed a pair of Golden Eagles rise from a cliff about a mile away. I knew that to be a historical eyrie site and wondered why a pair should be soaring over it? If they had eggs or small young one of them should have been on the nest. So I went over to check.

I soon found an actively-used eyrie and I quickly climbed up to look into the nest from the cliff top. There was a day-old chick and an unhatched egg in the eyrie. This seems negligent of the adults, but I am sure they were watching from up high, so I left the area completely as quickly as I could. I have seen this behaviour before. Perhaps the chicks are not as vulnerable as we would think, and the weather was warm and sunny that day after several days of cold, rain and snow. Maybe the adult female simply needed to get off the nest after seven weeks incubating and the male is less inclined to brood young than to cover eggs while she is off.

The soft down of an eaglet can just be seen above the fine warm nest lining of dried grass. An unhatched egg lies behind.


Double-red back on his feeding-lochan
I have spent the past few weeks studying Greenshank in Sutherland, in the northern Scottish Highlands, where I soon found the bird colour-ringed with double red, which was caught three years ago at the same site. He has also been seen since on the same wintering grounds in Suffolk. So he is very site fathfull for breeding and over-wintering.

This study is a cooperative voluntary one, done by a few members of Grampian and Highland Ringing Groups, with the aim to determine where Greenshank which breed in northern Scotland overwinter. But first we have to find the birds on their breeding grounds by searching the lochs for feeding birds and the moors for nesting birds. They are notoriously difficult to find.

A Greenshank lies low on its nest as I passed by - so easy to miss

Saturday, 1 June 2013

Long-tailed Tit nest
A Long-tailed Tit nest set in a fork of a birch tree
It has been a long cold spring in the Scottish Highlands this year, with the trees late in coming into leaf. Any birds which nest early, therefore need to be crafty in concealing their nests from predators. Long-tailed Tits, are masters of this. They build their domed nest with mosses and then dapple the surface with flecks of lichens gathered from the branches of neighbouring trees. The finished surface then blends in almost imperceptibly with the lichen-covered nest branch.

A well concealed Long-tailed Tit nest
Here an incubating bird watches from the entrance hole to the nest, set high on the right side. Even her face seems to merge with the colours of the lichen on the branch. In all, a marvellous example of camouflage.

A Long-tailed Tit looks out from its nest hole.