Tuesday, 28 July 2015

Ptarmigan on the rocks

I was up in the Cairngorms surveying ptarmigan last week, Rock Ptarmigan Lagopus muta, and they are well named for they are seldom seen far from rocks in the Scottish hills.

Their breeding season was about two-three weeks later than usual this year due to prolonged and extensive snow-lie. Many of the birds did not have any chicks, perhaps after failing to lay eggs or losing eggs or young? Others had very small broods of only single chicks compared with the usual average of  five or six chicks of about two weeks age - the age of the chicks that I did see.

Several hens which had no young had joined cock post-breeding moulting flocks and were roaming through the boulder fields skulking quietly amongst the rocks. When moulting, these birds typically prefer to walk away from any intruder as they probably feel more secure doing so while they have some flight feathers missing or only partly-grown.

They seemed so at home in the boulders, hopping and skipping over them with no effort at all. At times they were running over what to me was very awkward ground to walk over. They run over any open ground or large open slabs as they feel exposed to predators, then slow down once secure amongst the jumbled rocks again.

I left them to it and watched a snow bunting for a while, singing from the top of a large boulder. And in the meantime the ptarmigan settled down to rest amongst the rocks, disappearing to my eye as their colours blended with those of the lichen-covered boulders.

Here are a few shots of a hen showing her deft footwork on the boulders

Thursday, 23 July 2015

Wild Assynt

The jagged ridge of Stac Pollaidh
While surveying birds in the Highlands, one the extra joys is the magnificent hillwalking that, well just has to be done in such stunning scenery.

Pillars abound in these sandstone hills
I was in the Assynt hills last week and grabbed the best day of the summer for a great walk over one of these relatively small hills. They might be small, but each hill in the area has its own particular character and they pack an amazing variety of landforms into this quiet corner of the north west Highlands.

Sgurr an Fhidhleir points high into the sky
There is so much to explore, around every corner or over every bluff that I don't need to describe where I went. It's all great fun. One of the best experiences in walking these hills is to discover their secrets for oneself. There are landscape-scale features such as the impressive peaks, but take time to look at the finer lines, the hills are covered with little details which mirror the grander features.

A golden eagle added its shadow to the landscape
Then to add cream to the scene; I was walking along a ridge, carefully watching my feet, when a shadow drew over my path. I knew straight away that there was an eagle above, what else could have cast such a shape. And sure enough, I looked up and there was an adult male eagle displaying in deep dives as it cruised along the updraught from the ridge.

The day was already one of my best in the hills this year, now it was probably the best.

Suilven in the evening light
I stayed in the hills til evening, watching the rocks change colour in the sinking west coast light, until I had to finally turn my back on them til next time.

As ever, the trick to any good day is to be there, be out there, do something, do anything, then every once in a while a special day comes.

A wild west sunset

Friday, 17 July 2015

Golden Eagles Fledging

A Golden Eagle Aquila chrysaetos eyrie set in a large Scots Pine
It is now time for golden eagle chicks to leave their nests and I have been checking several sites to monitor their breeding success. The birds usually fledge in their tenth week, which is a long time for any bird to sit out as it slowly grows, filling in the hours, days and weeks watching the world go by between occasional feeds and long sleeps as it develops from a tiny downy chick to a sturdy eagle.

The adults began nesting in March, laid their eggs at the end of that month, incubated them for six weeks, and now will have to still provide food for the fledglings for a few months. So most of an adult golden eagle's year is filled by rearing young.

This eyrie was built in a multiple fork in the tree, a massive tree with a wide trunk and a magnificent spreading crown
- a true forest giant  
The fledglings' first flight can be a wobbly affair, and this bird will likely take a short one to a neighbouring tree branch. I was surprised that it hadn't taken that step as it was so well developed, but is was raining that day, so perhaps it was waiting for the best flight conditions for that important stage of life. Other birds I have checked lately have left the nest, one twin had gone off around a corner and was nearly a kilometre away from the nest, yet it's sibling was still in the nest - but testing its wings with big strong thrusts and hopping about the nest.

There will be young eagles jumping from trees and cliffs all over the Highlands this week, what a thought, but they will have testing times ahead.

This eyrie was a few metres wide and although the bird is fully grown size-wise, it can be distinguished as a chick by the bright yellow cere and base to its bill. Adults have less bright bills, they are more generally grey-coloured.

Sunday, 12 July 2015

Superb camouflage

Superb camouflage

While studying waders in northern Norway I was repeatedly impressed by the adaptation of these birds in their use of camouflage as their main defense from predators. Camouflage only works well if an animal does not move, relying on their cryptic plumage patterns to conceal them until the very last moment as potential predators, including humans pass by. This tends to make them rather difficult to study.

A Broad-billed Sandpiper hides amongst sedges

One species of wader which breeds in mires on the tundra is the Broad-billed Sandpiper Limicola falcinellus and they are very easily overlooked. These birds, about Starling-size, forage on mats of sphagnum moss on the edge of mire pools, creeping through the sedges. Their plumage has a background of dark browns like those of the muddy surface, with pale stripes that resemble the blades of the sedges. They match their habitat exactly.

Easier to see if you can pick out an eye

And if you think these are difficult to see, try to find the bird in the next photograph.

A Jack Snipe lies quiet amongst the sedges
Another species that lives in these mires is the Jack Snipe  Lymnocryptes minimus. Their plumage is like that of the Broad-billed Sandpipers, and the birds are of similar size. These two unrelated species have adapted similar plumages and behaviour, and they breed successfully, so their convergent evolution is evidence of the effectiveness of their survival strategy.

Even when seen close up they are not easy to discern

As I look down on these birds and admire their adaptation to their habitat, I often think to myself, how many have I walked past?

From above, the stripes on the Jack Snipe resemble the pale old leaves of the sedge

I study many cryptic species, but these waders are some of the the trickiest birds to find, they are true masters of the art of camouflage.

Once again, if it weren't for the eye....

Wednesday, 1 July 2015

Ousted cuckoo?

An adult male Lapland Bunting Calcarius lapponicus 

While surveying birds in northern Norway I came across a Lapland Bunting nest, which is not too unusual as they are common birds in the tundra there, although there was something different about this one. There were chicks in the nest as well as an unhatched egg and an eggshell, again nothing unusual there, except that the eggshell was of the wrong colouring for a Lapland Bunting egg.

The eggshell was a dull blue colour with brown freckling,
unlike the grey-brown background with scribbly line markings of the bunting egg

I immediately thought of a Cuckoo Cuculus canorus having laid an egg in the nest, so I checked the young to see if any were a cuckoo. None were, so what had happened? Thinking it through, the only explanation I can think of is that the buntings had detected the cuckoo when it hatched and ousted it from the nest.

The cuckoo egg did not resemble those of the buntings. It was more like a composite match between a Meadow Pipit Anthus pratensis and a Red-Spotted Bluethroat Luscinia svecica - two other common passerines in the area, and likely species to be targeted by cuckoos. Pipit eggs are grey-brown with dark brown freckles, and bluethroat eggs are dull blue coloured with tiny faint freckles. Yet this egg seemed to still pass unnoticed by the hosts.

The cuckoo eggshell on the left, the unhatched bunting egg on the right

I checked the nest a few days later and all the chicks, four, were alive and similar in plumage - all were buntings. So it seems that a cuckoo had failed in its attempt to dupe the buntings into rearing its chick. They perhaps detected the cuckoo chick when it hatched as different from their own and ejected it. This must happen more often than we assume, for there is an arms race between cuckoos and their hosts. In this case the cuckoo seemed to have laid its egg too late for the chick to gain the advantage of hatching first and ousting the buntings' eggs or newly hatched chicks.

Then, why had the cuckoo laid its egg in a bunting nest, were there too few pipits or bluethroat nests with eggs for it to parasitise in this late cold Spring?

The growing bunting chicks