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 of the 1st winter bird first reported at Newhaven Tidemills, East Sussex, on 21st September 2016.

More at:

Prince, M. (1996). Red-backed Shrike. Birds of Sussex. Sussex Ornithological Society, pp. 498-500.
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.

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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