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

Sunday, 28 June 2015

Red-spotted Bluethroats

An adult male red-spotted Bluethroat Luscinia svecica 

One of the more abundant passerines in northern Norway is the red-spotted Bluethroat, a robin-like bird that lives in birch and willow scrub, foraging for insects on the ground, while flicking from bush to bush. It is usually their tinkling song, or clicking contact call that gives away their presence, or thiier distinctive short flight low through the scrub.

An adult female red-spotted Bluethroat 

Most illustrations are of the brightly coloured males as they do have splendid throat colouring.  So I have added an image here of a female in breeding plumage. She has the basic colouring of the males, but duller and she has a darker, streaked breast than the males. This is because she needs to be less conspicuous while caring for her eggs and young.

Although conspicuous when singing from the top of a bush with their breast puffed up, most of the time, even male Bluethroats are secretive, passing quietly through the lower branches, dipping between shadows.

The intensity of the throat colouring varies between males and females, not all are bright, and the pattern varies in the amount of red in the spot, blue on the throat, or black, white and red on the lower bands. And I wonder how the birds see these colours, for the blue feathers have a shine to them, do the birds see an even brighter image via ultra-violet light sensitive visual perception?

The blue feathers on their throat, glisten in the sunshine, adding a marvellous metallic tint to the birds' plumage

Thursday, 25 June 2015

North Norway

A fresh burst of green opens over the northern Norway landscape as the birch leaves open

I'm in northern Norway for the second part of June, over mid-summer with twenty-four hour light. The main reason to be here is as part of a long-term study of breeding arctic waders, but there is so much wildlife activity, I thought I might add a general picture first.

There are high numbers of voles this year, especially grey-sided voles, and as such many predatory species are breeding. I saw a red fox the other day carrying a mouthful of voles back to its cubs. And other predators breeding include; rough-legged buzzard, hawk owl, short-eared owl, long-tailed skua and great grey shrike. Many people have heard of lemming population peaks, but they are not the only rodent in the arctic whose numbers fluctuate so dramatically, several vole species do also, and their numbers can influence the numbers of breeding animals too.

A Grey-sided Vole  Myodes rufocanus - an important food source for so many predators in Scandinavia

During the last peak in vole and lemming numbers a few years ago, I saw most of the usual predators breeding, but no great grey shrikes Lanius excubitor, that was because the rodents were in such high numbers over most of Scandinavia that the shrikes, which probably did not need to fly so far north to breed, stopped farther south where there were just as many if not even higher densities of rodents. However, this year there are shrikes breeding in the north and the nest illustrated held six chicks, of various sizes. They are all likely to fledge as the adults were bringing in plenty of food.

Six young shrikes lie quietly in their nest, some smaller than others,
 but all will likely fledge as there are so many voles about

As with great grey shrikes in winter, in summer they also spend most of their time perched high watching for prey, but the irony of these shots is that I photographed the vole directly below the nest tree while the birds were about twenty metres away. That was one very lucky vole, so far....

The adult shrikes sit on high perches in nearby trees

Saturday, 20 June 2015

Hilltop waders

A Dunlin Calidris alpina watches quietly - easily overlooked as it is little taller than the grasses

Last weekend I was surveying waders in the eastern Highlands, up on the top of the hills. It is on plateaux like these where Arctic-alpine waders such as Dunlin and Golden Plover breed, and they are beautiful birds in their breeding plumage. But they can be tricky to find.

The Dunlin can be obvious when they are displaying, chasing one another around the hilltops, singing their trilling song, but once they have eggs or chicks they hide. They are small, and even when they run away, they look not much larger than a small rodent, sneaking through the grass rather than flying away. Mostly, they will stand still and watch people walk by, oblivious of their presence.

A Dunlin runs through the grass

A Golden Plover Pluvialis apricaria stands alert, calling in alarm - difficult to not notice when watching over their chicks

Golden Plover are often as secretive when with eggs. Although some will walk or fly away and call in their peeping alarm call, many sit tight and watch people go by. But once their chicks have hatched the plovers are on constant alert, calling in loud repetitive peeps whenever a human or other potential predator approaches. Meanwhile, their chicks lie low in the grass or heather, their wonderfully golden down mimicking the yellow moss that underlies the taller plants.

Four golden plover chicks - a day old and soon ready to leave the nest 

Golden Plover chicks are some of the most beautifully coloured wader chicks, but the birds don't live on such anthropomorphic terms, don't yet perfectly matched to their hiding places up on the high mossy plateaux.

Golden balls of fluff - these plover chicks are marvelously coloured

Sunday, 14 June 2015

Long flight for food

A rock pipit collecting insects from the lawn

While staying with friends in Durness recently there was a steady trip of birds coming to the lawn to forage for insects, especially immediately after it was cut. The list included black-headed and common gulls, pied wagtails and meadow pipits. Special visitors were dunlin - it was great to watch these moorland/shore birds from the lounge window. But I was attracted by the rock pipits, for they seemed to be flying quite a distance down to the shore with food for their chicks. So, I followed their flightline to see just how far they were travelling.

The lawn where the pipits were catching prey, seen from inside the house,
with the Ferryman's Cottage in the background

I was impressed with what I found. The first step, as far as I could follow the birds from the window, brought me to the shore at the bottom of the garden where I found a pair of rock pipits feeding young in a nest in a grassy bank above the tide-line. But those birds were catching insects locally, less than fifty metres from their nest, they weren't the ones from the lawn. So I watched and waited for the lawn birds to fly past. And they did. They came down over the bank then flew low over the water and set out across the estuary with their catch.

The kyle between the mainland and the Cape-side,
the rock pipits were carrying food back to their nest below the cottage

The estuary is the Kyle of Durness which separates the Cape Wrath peninsula from the mainland. I watched the birds fly right over the low tide sands and water channel, several hundred metres wide, and for a total journey of over a kilometre, to feed their young in a bank below the old Ferryman's Cottage. Why the birds were flying so far to collect food is intriguing, but I am never amazed by what I learn about wildlife, simply ever-more respectful of their capabilities.

A brood of four rock pipit chicks lie quiet in their nest - waiting for their parents to deliver more food