Tuesday, 10 July 2018

Three alpine/arctic specialist birds

The path into Coire an t-Sneachda
I went for a walk in the Cairngorms last week, to count Ptarmigan Lagopus muta and their brood sizes, as they mostly have well-grown chicks now. Ptarmigan are an alpine/arctic bird so they are restricted to such ground in Scotland and if we want to see them we have to do so on their terms. Two other species which are such specialists are Snow Bunting Plectrophenax nivalis and Dotterel Charadrius morinellus, and I saw them both while looking for the Ptarmigan.
The castellated rim around the top of the corrie cliffs
I walked into the hills via Coire an t-Sneachda and took the Goat Track up onto the plateau. A fine spectacular route through a boulder field and under the crags.

The twin pinnacles from above the rim
I passed the common generalist hill birds, Wheatears Oenanthae oenanthe and Meadow Pipits Anthus pratensis in the corrie, and a couple of Ptarmigan, then as I neared the summit I heard a Snow Bunting singing. His song ringing around the rocks on such a clear windless day.

A handsome Snow Bunting singing from the edge of the cliff
When I reached the top, I sat on the cliff edge for a while and soon realised that the Snow Bunting was flitting between a few rocky points which he was using as song-posts, one right by me. And he was confiding, he seemed to accept my presence and came to sing next to me. He would fly from a cliff across a gully then slowly descend in a parachute drop to his post next to me, singing as he came down.

A cock Ptarmigan sits on a rock ledge overlooking the corrie floor 200m below

The Snow Bunting was easy to see as he was making himself conspicuous by his singing display. The Ptarmigan were much more secretive. But just around a rocky corner from the bunting I noticed a male sitting quietly and inconspicuously on a rock more fitting for a bunting song-post than a Ptarmigan perch. He was squatting there watching over his hen who was in the gully below, feeding on the mountain herbs, Heath Bedstraw Galium saxatile and Alpine Lady's Mantle Alchemilla alpina.

If he hadn't moved I would probably not have seen him

That female didn't have any chicks, and it was probably too late for her to re-lay if she had lost her first clutch of eggs. So they would probably have the rest of the season off from raising young, then join into a flock of failed breeders and males who would soon leave their partners to rear their chicks alone.

A hen Ptarmigan, she was alert and watchful as she had chicks
- a different colour from the males, more suiting to the heath and moss habitat

The next Ptarmigan I found was a female with four chicks, who were feeding on the top edge of the next corrie, where the herb-rich cliff vegetation merged into the sparse windswept plateau vegetation.

She had four chicks - two can be seen in this photograph

This was prime Ptarmigan habitat, a loose mix of boulders for cover from predators and weather, and food plants growing close to the base of the rocks. They would never have to wander far from cover to feed, and if it was difficult for me to find them it would be difficult for any predators. Such mountain habitat might seem harsh or inhospitable to some anthropocentric humans, but to Ptarmigan it is perfect. And I like it too.

The Cairngorms plateau spreads out above the cliff edge
Braeriach is the highest hill in the background

The high ground of the Cairngorms, above the cliffs, is mostly sweeping, rolling plateau. There are Ptarmigan throughout this habitat of wind-scoured boulders, gravel and Juncus trifidus heath, but the main specialist bird of this ground is the Dotterel. I have studied these birds for over thirty years, and although I am very familiar with them, it was still good to see some. They fit the landscape so well. Although waders, they spend their non-breeding time in arid north Africa, then fly north to breed on dry mountain/arctic heath. I have only once seen one stand in water. The birds in Scotland are one of a few species that can live on the highest ground, and select to breed only there. They were the third such alpine/arctic specialist bird species I saw that day, the high three.

A male Dotterel skulks in the alpine heath - mostly Juncus trifidus  

I wasn't there to study Dotterel that day, so although I did see a few, I walked on by. The males mostly had chicks - they incubate the eggs and rear the chicks alone, but this one was with a female, so he had perhaps lost his first clutch and she might have been about to lay another for him. 

He showed himself briefly as he ran between the tussocks

The female Dotterel are bigger and brighter coloured, but she never showed herself clearly and I didn't chase her. I have seen hundreds before. I simply appreciated them, took a few long-lens shots as the male popped close, and I walked on by. There are too many human visitors, hillwalkers and bird-watchers to that area, I didn't want to add to their disturbance.

I was happy, I had spent a perfect day in my favourite habitat, one I share with three special birds.

Sunday, 1 July 2018

Defence strategies of tundra birds

A male Spotted Redshank comes close in defence of his chicks
I spent the past two weeks in northern Norway studying birds, mostly waders and even though I am familiar with them, I continue to be impressed by the efficiency of their stategies in defending their eggs or chicks.

A Spotted Redshank can hide or run when a predator approaches
Most Spotted Redshank pairs split soon after the eggs are laid and the male incubates them, then rears the chicks alone. The chicks stay in the nest for the first day then they can walk more than a kilometre to reach a feeding marsh.

An male adult Spotted Redshank in breeding plumage - no other bird like it 
When danger approaches, the adult flies close to the intruder and pipes loudly, very loudly, causing confusion in a potential predator's mind - mine anyway. Meanwhile, the chicks run away or hide until the danger passes.

Incessant piping
Other waders, such as Whimbrel fly up and around any potential predator, calling in alarm, or guidance to their chicks. We as humans, cannot tell which, but the chicks can either run or hide. What vocal signals do the adults give to do either?

A Whimbrel up a tree - from where it is safe from ground predators and it can see its chicks hiding in the ground vegetation
The main terrestrial predators are Red Fox and Stoat, but there are also Ravens and Hooded Crows which can take the chicks. Perhaps that is one reason why the chicks can either hide or run.

Wood Sandpipers habitually sit in trees when protecting their chicks
The waders usually have four chicks, so scattering to feed, hide or run gives the others a chance if a predator finds one of the brood.

When on eggs =- Wood Sandpipers sit tight on approach
If they have eggs, these birds usually adopt a different strategy, one of sitting tight on their nest, relying on camouflage and concealment to avoid detection by any predator, until the last moment when they burst fom their nest to escape capture.

very tight
Once they leave their nest, these waders will call in alarm, then either fly away and try to distract the predator, or adopt a rodent-run display, where they either impersonate a rodent or a bird with a broken wing to lure the predator from their nest.

A Broad-billed Sandpiper gives a distraction display, pretenting to be a rodent or have a broken wing
- to lure me from its nest and eggs 
If anyone has been with a dog when it has disturbed a nesting bird they will know how efective this display can be. Most dogs, especially town dogs fall for this trick and run after the bird well away from the nest.

Jack Snipe sit extremely tight on their nests 
Jack Snipe are one of the tightest sitting waders, I am sure I must have stepped over birds on their nest. And when one sees how well they are camouflaged in the mire vegetation, I know why.

Jack Snipe nest just above the water level below the marsh vegetation
- they see the habitat differently from we humans 
It is not only waders which behave like this, other ground nesting birds act similarly, such as Willow Grouse. They have larger clutches and broods, perhaps 7 - 11 eggs or chicks, so the scattering of the brood if they run or flutter away is especially successful at saving at least part of the brood.

You all saw the male Willow Grouse, on the right first, maybe then seeing the female afterwards
Their chicks are most vulnerable in their first week, but after that they can fly in a fluttering flight for several metres, then more as they age.

A two-day old Willlow Grouse chick sits quietly and motionless - to avoid detection while its parents try to distract me
The male grouse is more brightly coloured than the female, and this one was more demonstrative to me. The female was running around low and farther away from me. That way, if any predator managed to kill any bird it would likely be the male. He is more expendable, if he died the female could rear the chicks by herself. So, a test of his fitness as a mate is not only his bright plumage, but his ability to escape predation which that plumage might attract.

The male Willow Grouse came within metres in attempting to lure me away from his chicks