Sunday, 25 September 2016

Autumn passage …

Red-backed Shrike (Lanius collurio)







The beautiful Red-backed Shrike L. collurio would once have been the most familiar of the shrike family in both Sussex and the UK for it bred widely, if sparsely, throughout much of England and Wales. However, it sadly declined throughout the 19th and 20th centuries becoming extinct as a breeding bird in Britain from 1992 until 2010. In line with its collapse nationally, the Sussex population, although never large, was certainly declining in the 1930s and the last confirmed breeding was a pair on Ashdown Forest during 1964-68. Other pairs have been recorded, such as those in 1977, 1981 and 1993 but none stayed longer than two days.

Along with many other migratory species of bird, L. collurio is in great danger when travelling to and from their wintering grounds in Africa, with many trapped and killed en route. In Sussex, it is now only seen as a very scarce passage migrant. The best chance of seeing this attractive species now is during autumn passage. Of the 51 birds recorded in the county during 1995-2011, 37 were during August-October, with a clear peak in September. The above images are a selection from a session with the 1st winter bird first reported at Newhaven Tidemills, East Sussex, on 21st September 2016.

More at:

Sennitt, M. (2014). Red-backed Shrike. The Birds of Sussex. Thetford: British Trust for Ornithology (BTO) Books on behalf of the Sussex Ornithological Society, pp. 389-390.
Prince, M. (1996). Red-backed Shrike. Birds of Sussex. Sussex Ornithological Society, pp. 498-500.

Saturday, 17 September 2016

A yellow thought in a purple shade …

Clouded Yellow (Colias croceus)



Of the three species of Clouded Yellow generally regarded as being found in the British Isles, the Clouded Yellow (Colias croceus), Berger's Clouded Yellow (C. alfacariensis) and Pale Clouded Yellow (C. hyale), C. croceus is by far the commonest and the easiest to identify; alfacariensis and hyale are both similar in appearance and extremely rare immigrants.

When observed in flight, the orange appearance of croceus is unlike any other British butterfly. When settled, the lemon-coloured underside of croceus allows us to distinguish this species from both alfacariensis and hyale which both have much paler undersides. This diagnostic generally holds true even in the helice form of female croceus where the orange colouring is replaced by a delicate creamy white. Distinguishing alfacariensis from hyale in the field is a completely different matter and unless one is accustomed to regularly seeing either species it would be very difficult to make an accurate identification of the adult insect.

C. croceus has a distribution befitting a strong-flying, highly-migratory species and can be found almost anywhere in the British Isles including coastal cliffs, open downland, and fields containing its larval foodplants. Many immigrants remain near the coast where they feed, mate and lay eggs. Others disperse inland and this species can be found in both Scotland and Ireland during good seasons. Numbers vary greatly from year to year but in 1947, one of the infrequent mass immigration years, an estimated 36,000 adult butterflies were recorded in the British Isles.

The above images show (i) a female nectaring from Devil’s-bit scabious and (ii) a female at rest during the early evening sun.

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Sunday, 4 September 2016

Selvedg'd Heath Eye (Petiver, 1717) …

Small Heath (Coenonympha pamphilus)


Despite its contemporary British vernacular name, C. pamphilus is not confined to heathland and can be found in a wide range of habitats particularly those that are more open in structure, such as grassland, heathland, railway embankments, disused quarries, meadows and coastal dunes. It occurs only sparingly in woodland where it can be found in ones and twos along wide woodland rides.

The main distinguishing feature of this discreet species is that this is the smallest of the Satyrids found in the UK and is closer in size to a Common Blue (Polyommatus icarus), Brown Argus (Aricia agestis), or even one of the golden skippers than its relatives, such as the Meadow Brown (Maniola jurtina). However, its weak fluttering flight is quite dissimilar from these species and is relatively easy to identify in the field. The sexes are alike yet females tend to be a little larger, more rounded and generally paler than the males and her eyespot is typically not so prominent. This delightful though often overlooked little butterfly always settles with its wings closed, where the eyespot on the underside of the forewing is usually visible, acting as a decoy to potential predators. The forewings are tucked behind the hindwings when roosting for long periods, or during episodes of dull weather; the butterfly looking quite inconspicuous as the browns and greys of the underside of the hindwing blend in with their surroundings.

A freshly emerged male having just alighted on a grass stem is pictured above.

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Tuesday, 30 August 2016

Variation and form ...

Common Blue (Polyommatus icarus)

Surely one of our most beautiful insects ...





P. icarus is the most widespread member of the Polyommatinae found in the British Isles but has significantly declined with the destruction of much semi-natural herb-rich grassland through agricultural intensification. It now lives in discrete colonies on remaining herb-rich grassland and disturbed sites where its larval foodplants can be found. The primary foodplant is Bird's-foot Trefoil (Lotus corniculatus). Black Medick (Medicago lupulina), Common Rest-harrow (Ononis repens), Greater Bird’s-foot Trefoil (Lotus pedunculatus), Lesser Trefoil (Trifolium dubium) and White Clover (Trifolium repens) are also used.

Two broods are typical in the southern counties of England and one brood further north. Occasionally, in favourable seasons, there may be a third brood. In good years, adults may be seen as early as the middle of May on more southerly sites. These peak at the end of May, giving rise to a second generation that emerges in the second half of July, peaking in the middle of August. Colonies in northern England and Scotland typically have a single brood that emerges in June, reaching its peak in July. I am currently seeing freshly emerged individuals of both sexes in local Surrey and Sussex locations. Whilst the male has bright blue uppersides, the female is primarily brown, with an extremely variable amount of blue and extent of spotting. Not only can this be noted in distinct geographical populations but also within the same seasonal population. P. icarus is therefore the subject of a vast number of named and unnamed aberrations. The brown form of the female is sometimes mistaken for the Brown Argus (Aricia agestis) and vice versa.

The above images, in descending order, show (i) a male from 2015, (ii and iii) two females from 2016, and (iv) an extremely blue female referable to ab. supra-caerulea, Oberthür (1896) from St Mary’s, Isles of Scilly, 2012.

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Sunday, 14 August 2016

A matter of perception ...

Meadow Pipit (Anthus pratensis)




Often overlooked due its unfortunate reputation for being an uninteresting species, A. pratensis is one of the most widespread and ubiquitous of all UK species. However, flocks of migrant A. pratensis are always worthy of closer scrutiny since they can be a good carrier for wagtails and rarer pipit species.

In spring, A. pratensis arrives back in Sussex to breed and many more pass through heading further north. Passage can begin in late February, but March and, to an extent, April are the key months. Although some birds may remain in Britain to overwinter, in autumn, most British birds head south, with many passing through Sussex on the way. Autumnal movements gain momentum in September through October and are often very evident at coastal sites with birds moving along the coast. Confusingly, such movements can be eastwards or westwards but the latter generally predominate and are often into the prevailing wind.

Throughout Sussex it is a bird of open, extensive rough and grassy habitats, from sand dunes and salt marshes to wet grassland, heaths and unimproved chalk grassland, where it feeds and nests on the ground. Take more attention next time you see one and appreciate the fact that it is common …

References:

Scott-Ham, M. (2014). Meadow Pipit. The Birds of Sussex. Thetford: British Trust for Ornithology (BTO) Books on behalf of the Sussex Ornithological Society, pp. 542-543.
Scott-Ham, M. (1996). Meadow Pipit. Birds of Sussex. Sussex Ornithological Society, pp. 398-399.

Wednesday, 3 August 2016

The sleeper ...

Small Tortoiseshell (Aglais urticae)

Chiddingfold Forest, 2016



The beautiful Small Tortoiseshell A. urticae can turn up almost anywhere and appears in gardens throughout the British Isles. It is one of our most successful butterflies. As its scientific name correctly suggests, it is most-often seen where nettles grow in abundance; both Common Nettle (Urtica dioica) and Small Nettle (U. urens) are used for egg-laying and larval nutrition. A. urticae is also frequently encountered whilst hibernating in an outbuilding, such as a garage, shed or barn, where they may be found in the company of other individuals. Further hibernation sites include hollow trees and woodpiles. I personally experienced some fifteen individuals overwintering in an old converted tractor shed last year. They were surprisingly first seen to be entering hibernation on 31st July 2015. They stayed in this state for eight months and only occasionally showed signs of any movement.

The adult butterflies can be seen on the wing at any time of the year, even on the last days of December or first days of January if the temperature is high enough to wake them from their dormancy. However, adults normally emerge from hibernation at the end of March and start of April. There are typically two broods each year, except in the north, where there is usually only a single brood. Whether single or double-brooded, the butterfly can be a familiar sight in late summer as it imbibes nectar to build up essential fats in preparation for its period of rest.

The above images show two separate males, the first, exhibiting dorsal thermoregulation on a forestry track in early July, the second, having successfully overwintered in the adult form, resting on a log pile in early April; the antennae tucked tightly between its forewings and showing the exquisite camouflage of the underside.

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Monday, 1 August 2016

15th August 1832 …

Lulworth Skipper (Thymelicus acteon)






To the lepidopterist the name James Charles Dale (1791-1872) will always be associated with the discovery of a butterfly new to Britain, Thymelicus acteon, the Lulworth Skipper. It is recorded, that on the 15th August 1832, Dale, having journeyed around twenty miles on horseback from his home at Glanvilles Wootton, reached Durdle Door, near Lulworth Cove. Here he found considerable numbers of acteon along the cliff tops. However, it was not until John Curtis reported Dale’s discovery in Volume 10 of his British Entomology, published in 1833, and named it the Lulworth Skipper, that the discovery was announced in print.

The female (pictured above) is quite recognisable from the pale orange crescent on her forewings, which is either lacking or very feint in the male. The male is generally darker in colour and has a distinctive sex brand on its forewings. As its name suggests, the distribution of this species is centred around Lulworth in Dorset, between Weymouth and the Isle of Purbeck. Colonies are most often encountered on south-facing, sheltered slopes, on chalk or limestone grassland, where tall patches of Tor-grass (Brachypodium pinnatum), its larval foodplant, can be found. In Britain, this species is at the northern limit of its range and is rarely found more than 5 miles from the coast.

The above images, in descending order, show (i and ii) a female on its larval foodplant, (iii) a freshly laid batch of eight eggs in the dried stem of B. pinnatum, (iv) typical acteon habitat overlooking Lulworth Cove with B. pinnatum in the foreground and (v) the view looking towards the northwest from its home on Bindon Hill.

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