Monday, 25 July 2016

Clifftop lepidoptera

A pair of Six-spot Burnet Moths Zygaena filipendulae on the stem a red-campion flower
with the empty cocoon of the female below
I went out to the sea cliffs on one of those warm days last week, when it really felt like full summer with blue skies and sunshine. And the lepidoptera thought so too.

My initial reason for the trip was to spend a while watching the seabirds, so I headed out to some of the best viewpoints I know to see the kittiwake chicks which were quite large and would soon be fledging. Most of the guillemot chicks had left their ledges, but there were still some about as well as razorbills, shags and herring gulls. The fulmars were not long hatched so they will be on their nest ledges for months yet.

However, it was while walking between viewpoints that I noticed the flutter of activity along the cliff-top. There were butterflies and moths flitting all across the grassland and heath. The cliff-tops around the coast of Britain hold some of the least disturbed habitats in the country, for they are seldom grazed, and wild flowers thrive there. I shifted my attention.

The female on the left - her wings are still not fully unfolded after emerging

The most abundant species were Six-spotted Burnet Moths. The adult males had already emerged and were patrolling over the grasses and herbs for females. These were only just emerging that day, probably under the influence of the hot sunshine. The males detect them by scent and there were clusters of males in some places, swarming over single females as they emerged from their cocoons. Once one male had coupled with a female, the others seemed to accept they had lost their chance to mate with her and went away to seek another. One female had been found by a male before she had fully emerged and the two moths lay attached as she slowly pulled out of her cocoon and extended her wings.

A frenzy of males swarm over the source of a female's scent 

There was plenty bird's-foot trefoil about, so once their eggs were fertilised, the females would lay their eggs on the leaves of this favourite food plant of the caterpillars.

A male couples with a female before she has fully emerged from her cocoon

While the Burnet moths were colonial, the butterflies were mostly single, with males chasing away any intruders of their species, or even those of other species. While at the same time trying to attract and mate with any females that came through their territory.

The herb-rich clifftop grasslands

Meadow Brown butterflies were the most common in the grasses, because the caterpillars feed on various grasses. However, although there were lots of them about, whenever I tried to follow any to photograph, they would wander over a large area then dip into the sward, fold their wings and disappear in the strong shadows. It was easier to stay still, wait til they landed beside me and then take a photograph.

A male Meadow Brown Maniola jurtina  

The females were especially elusive, skulking in the tallest vegetation, safe from predators. Although there were few passerines about that would have taken them; mostly meadow and rock pipits and they prefer to hunt on short sward and generally eat small insects.

A female Meadow Brown

The male Common Blues were the most defensive of their territories and quickly chased off the large Browns as soon as they appeared on their patch.

A male common Blue Polyommatus icarus

The adult Blues were feeding on bird's-foot trefoil and clover, both of which are also food plants for their caterpillars. So all in all, the rich flora on the cliff-top with the abundant grasses, trefoil and clover was clearly a good habitat for the moths and butterflies.

Sea-cliffs are always great to visit for wildlife, but on that warm sunny day it was especially worth exploring. The seabirds were still on the cliffs, busy as ever, and the lepidoptera were busy on the tops. Let's hope these little sanctuaries never get destroyed,

A female Common Blue

Tuesday, 19 July 2016

Honeysuckle Eyrie

The Golden Eagle breeding season is almost over, with most of the chicks fledging soon or having already left their nest. This one was jumping about and exploring its surroundings, taking very short flights between the nest and an adjacent ledge. It hadn't yet taken its first full flight a few days ago, but it might have done so by now as I write this.

This bird has been reared in one of my favourite eagle eyries, set below a deep overhang with a lush growth of honeysuckle which was in full bloom. How did the honeysuckle get there? Perhaps the eagles brought in sprigs to add to the eyrie and seeds came with them. The plant is certainly vigorous, probably a result of fertilisation from the droppings and prey remains in the eyrie.

This the first time I have seen a chick fledge from that nest since I first knew it in 1982. The birds have alternative nests on nearby cliffs and last year they raised a chick in one of those, which is very high and rather inaccessible. In the past, the birds' breeding efforts usually failed if they tried to nest on this relatively low and accessible crag. Disturbance was the most likely cause for their failure as they were usually successful if they nested on the big cliff. This territory is on ground once used for sheep rearing, and now that sheep numbers have been greatly reduced in that area and in the Highlands in general, there seems to be less disturbance.

There was a heavy mist when I checked the eyrie, some would call it rain, but the chick was well sheltered by the overhang. I was soaked through. The chick had a lovely big nest to play about in, and the view from the cliff is quite dramatic. What a wonderful eyrie to grow up in.

Monday, 18 July 2016

Lots of insects - and birds

A Yellow Wagtail Motacilla flava eyes off a crane fly Tipulidae

As a final post on my recent trip to Norway, I would like to mention the insects, the profusion of insects which make it possible for so many migrant birds to breed in the tundra and birch forests. The most noticeable insects are the mosquitoes, of which there are thousands, millions, and all the females are intent on sucking blood. This is probably the most deterring factor for me to visit the arctic, but for the birds it is perhaps the most alluring factor. And many other insect species also thrive in high numbers, all adding up to form the rich feeding grounds for birds to rear their chicks. Of course, on balance, it is worth the discomfort to study the birds.

Mosquitoes torment a Short-eared Owl Asio flammeus chick

However, not all birds eat insects. The owls eat voles and have to endure the mosquitoes like we humans.

Male Red-spotted  Bluethroats Luscinia svecica are one of the more conspicuous birds in the birch forests
they often perch on on high perches when hunting for insects

The most obvious and abundant passerines feeding on the insects are the Yellow Wagtails, Red-spotted Bluethroats and Willow Warblers Phylloscopus trochilus. However, in some years the weather can be cold and insects scarce. Then the passerines are scarce too, as so often happens with bonanzas, it can be a case of boom or bust. The migrant birds clearly take a risk in flying so far north to breed, but the risk must be worth taking or else evolution would have selected against such behaviour.     

Female Red-spotted Bluethroats are one of the less conspicuous birds in the birch forest
when they hide on their nests 

The waders also rely on the insects. The adults eat them, often probing for the larvae, and the chicks eat them, often as adults, picking emerging mosquitoes as they lie on the water surface. If only they could eat a few more mosquitoes before they eat me. But now that I am back south and away from the mosquitoes, birch flies and horse flies, I have cast them out of my thoughts. I can now concentrate on the good memories; the wealth of flora and fauna in arctic Norway. That was a great trip.

Wood Sandpipers are very conspicuous when they have young.
They often stand on high perches overlooking the mires where their chicks are feeding
- even in the rain

Sunday, 10 July 2016

Arctic Norway Flora

A northern Norway landscape showing a mix of  tundra with small pools and mires,
a large lake, birch forest and high mountains 

While I was in northern Norway studying birds recently, I took the opportunity to note and familiarise myself with the plants. Below is a small selection of them; they are are all common in the area, some abundant and forming large proportions of the ground flora.  

Arctic Bramble Rubus arcticus

The Arctic Bramble was growing in small clumps, often only tens of centimetres tall and wide, very unlike its sprawling southern relation. I found it growing on hummocks in wet mires and on the forest floor, in sheltered, wet conditions. The flowers are delicate and like so many of northern species, short-lasting. I wondered how the fruit would taste, it is famed for its flavour.

Bog Bilberry Vaccinium uliginosum

Bog, or Northern Bilberry was one of the common ground covering plants on the hummocks in the mires. The drooping pink flowers would soon drop their petals and the dusty blue fruit would form. There are so many fruits on the tundra in autumn, forming a rich food source for the animals before the onset of winter.

Blue Heath Phyllodoce caerulea

Blue Heath is a very rare plant in Britain, confined to a few small locations in the Scottish Highlands. In northern Norway it is abundant, growing thickly on drier ridges and hummocks. It is one pant that seems to have taken advantage of the loss of lichens as mentioned in the previous post.

Alpine Bartsia Bartsia alpina

Alpine Bartsia is one my favourite alpine/arctic plants. The tubular sepals enclose the flowers, and the rich blue colouring flushes through all the uppers parts of the plant, making it difficult to make out where the flowers are in the crown. The downy surface on the leaves and flowers are a feature common on cold-climate species.

Wood Cranesbill Geranium sylvaticum

Wood Cranesbill is found widely in European and British woodland. In the far north, it grows in the birch forest and is commonly found on roadside banks. This is not a northern specialist plant, rather an example of one that has an extensive range. It is just as good to find old friends as to find new ones.

Blue sky and clouds reflected in open water surrounded by floating mire