Saturday, 30 April 2016

Moorland magic ...

Black Grouse (Tetrao tetrix)

The Black Grouse T. tetrix is typically regarded as a bird of early successional forest, either coniferous or birch, and of forest-edge habitats. Following large scale reductions in the extent of natural forests, T. tetrix are now found in structurally similar habitats, such as mosaics of moorland and heathland, early stages of coniferous plantations, rough grazings and traditionally managed meadows. They are well known for the early morning displays of the male (a selection of images above). At first light they gather at clearings known as leks, where they display to attract a female by strutting with their tails spread wide, their heads held low and their bubbling calls and posturing. Leks are visited all year round but the peak of activity occurs during the spring when the females attend and mate with the males. The most dominant males hold the best positions at the lek and mate with most females. As dawn breaks and the sun rises above the beautiful moorland habitat, the sights and sounds of lekking T. tetrix is an experience that is rarely forgotten.

Unfortunately, during the last century, they have been declining throughout virtually all of their European range. In Britain, the decline has been considerable over the last 150 years and the species is now mostly confined to Scotland and northeastern England, with a small number still resident in Wales. They used to be common throughout southern and central England from Lincolnshire and Norfolk to Hampshire and Cornwall. By the late 1960s they had disappeared from all of the southern part of their range. They are currently disappearing at rates of between 10% and 40% a year in some areas. T. tetrix is listed on the UK Red List of Birds of Conservation Concern (December 2015), and is a priority species for which a UK Biodiversity Action Plan has been produced. It is therefore vital we take our responsibilities seriously to avoid harming these wonderful upland birds.

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Monday, 18 April 2016

The herald of spring ...

Orange-tip (Anthocharis cardamines)

Along with the first primrose A. cardamines is a true indicator of spring, being one of the first butterfly species to emerge that has not overwintered as an adult. The male and female are very different in appearance. The more-conspicuous male has orange tips to the forewings, which give this butterfly its name. These orange tips are absent in the female and she is often mistaken for one of the other whites, especially the Green-veined White (Pieris napi), Small White (Pieris rapae) or Wood White (Leptidea sinapis).

This beautiful insect is found throughout England, Wales and Ireland, but is somewhat more local further north and especially in Scotland. It inhabits a wide range of habitats, which include flower rich country lanes, hedgerows, riverbanks, woodland margins, rides and damp sheltered meadows where its main larval foodplants can be found; Cuckooflower (Cardamine pratensis) and Garlic Mustard (Alliaria petiolata). In most regions this butterfly does not form discrete colonies and the male, in particular, appears to wander in every direction as it flies along hedgerows and woodland margins looking for a mate or sources of nectar.

The above images from a favoured Sussex site …

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Saturday, 9 April 2016

Ferring ‘St’rife …

Small Tortoiseshell (Aglais urticae)

The Small Tortoiseshell A. urticae is one of our most familiar and iconic butterflies, appearing in gardens throughout the British Isles. Unfortunately, this beautiful insect has suffered a worrying decline, especially in the south, over the last few years. It has always fluctuated in numbers, but the cause of a recent decline is not yet known, although various theories have been proposed. One is the increasing presence of the parasitic tachinid Sturmia bella (Diptera: Tachinidae), due to our warming climate - this species being common on the continent. The fly lays its eggs on leaves of the foodplant, close to where larvae are feeding. The tiny eggs are then eaten whole by the larvae and the grubs that emerge feed within their host. The larva of S. bella eventually kills its host and emerges from either the fully-grown larva or pupa before itself pupating. Although S. bella attacks related species, such as the Peacock and Red Admiral, it is believed that the lifecycle of the Small Tortoiseshell is better synchronised with that of the fly and it is therefore more prone to parasitism.

A recent visit to Ferring Rife in West Sussex produced around 20-25 overwintered A. urticae. Considering counts of up to 194 were recorded by Neil Hulme in 2013, with good numbers also recorded during the 2014 and 2015 seasons, the site appears worryingly less productive this year. Whether this is due to what appears to have been a change in management regime remains to be seen. What we do know is that this site has supported the largest population of A. urticae in West Sussex and has doubtless played a fundamental role in the species’ local recovery since at least 2012.

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Saturday, 2 April 2016

Aerial antics ...

Peacock (Aglais io)

The Peacock (A. io) has to be one of my favourite butterflies, not least because the adults can be seen at almost any time of year, with warm weather waking them from hibernation. Generally single-brooded, in good years a small second brood may sometimes appear. The majority emerge from hibernation at the end of March and beginning of April. These mate and ultimately give rise to the next generation that emerges at the end of July.

Males set up territories around midday, often on the sunny side of a wood, where they wait for a passing female. Males will immediately fly up at any dark object, which is one way of sexing this species since the two sexes are very difficult to tell apart, being almost identical in appearance. It is not uncommon to see two or more males rising rapidly into the air as they fight for aerial supremacy. When a female is found she flies off, trying to escape the male that is in pursuit. If he succeeds in staying with her then the pair may mate.

The above images depict three males from today …

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