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August 2013

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Red-legged Partridges, Sheila Sims
Red-legged Partridges, Sheila Sims

Family groups of Partridges will be feeding in the fields, now, or running in front of your car forgetting they have wings – they’re so reluctant to take to the air! Our native Grey is not as common as it used to be, so the one you see will almost certainly be the Red-legged or, as it is also called, French Partridge. First introduced to Britain in the sixteen hundreds as a game bird, it has been very successful and has become a common farmland resident. It feeds mainly on seeds, with some roots and vegetation, and the young will also take insects to boost their protein intake. The nest of the Red-Legged Partridge is a sparsely lined scrape on the ground and they often have the unusual habit of preparing two. One clutch is incubated by the female and the other by the male – egg losses are quite high, though, as they forget to cover the nest, when they leave to feed, providing tasty meals for predators.

Later, this month, adders start to produce their young. Unlike Grass Snakes, they do not lay eggs but retain them inside their bodies and give birth to live babies.

A mystery disease is causing Britain’s oak trees to ‘bleed’ and it is the older ones that seem to be most at risk. It is identified by dark, weeping patches on the bark and can kill a tree within four years. Many at the National Trust estate, Blickling Hall, Norfolk, have been affected but, as yet, it is unclear as to what is causing this. Among the possible culprits could be a beetle called the Oak Jewel, its larvae have been found near infected trees, or new bacteria that have been discovered on the stems. Maybe it is neither of these, though; research is ongoing.

The RSPB nature reserve at Titchwell Marsh is one of Norfolk’s most beautiful and work that has been done in recent years has created a new tidal salt marsh, bringing large numbers of ducks and wading birds. Sea defences have also been reinforced to protect the reserve and provide habitats for water voles, bitterns and many other species. It looks beautiful here in the summer when the Sea Lavender flowers transform the marsh into a purple haze.

School holidays are here and families head to the beach to enjoy the sea and the wildlife but there is far more than seals and birds, if you look. Turn over stones, look in rock pools and along the tideline and you will find a great variety of animals. Fish, crabs, jellyfish, sea anemones, shellfish and many invertebrates live here but care is needed if they are handled as some are easily damaged and some nip or sting! Children love to look at these things but it is kind to leave everything as you found it and return animals to their homes.

Small Tortoiseshell, Sheila Sims
Small Tortoiseshell, Sheila Sims

This summer, certainly in our region, we have seen far more Small Tortoiseshell butterflies than usual, which is good news for this beautiful insect, as its numbers have declined in recent years.

The female lays her eggs on a nettle, which is the food plant for the young caterpillars. While they are small they live in a communal web, which they spin near the top of the plant, leaving to feed during the day and also at night. If they are disturbed they jerk their bodies from side to side which helps to confuse predators. As the caterpillar grows, it moults its skin – this happens a few times until it is mature. It will then pupate, each turning into a chrysalis, and after two to four weeks, depending on temperature, the butterfly emerges. There will usually be two broods a year and when the autumn comes they hibernate, often in outbuildings or hollow trees.

There is usually more than one reason for the decline of any species; climate, habitat destruction, intensive farming and the use of pesticides all play their part and have most certainly contributed to reducing the numbers of the Small Tortoiseshell. One interesting study that is being carried out, involves an ‘alien’ which arrived from the continent in the late nineties – a parasitoid fly called Sturmia bella.

It lays its minute eggs on a nettle leaf and some are eaten by the young caterpillars as they feed. Each egg hatches into a tiny maggot which then (look away now if you’re having your lunch) proceeds to eat the caterpillar from the inside, carefully avoiding vital organs so as not to kill its dinner before it is ready to leave. How clever is that! Then, usually after the caterpillar turns into a chrysalis, the maggot abandons its dead victim and pupates, to eventually emerge as an adult fly. It’s a gruesome business and although it is not the only parasitoid to invade the Small Tortoiseshell, it is thought that it may play a significant role in the decline of this once common butterfly, but the jury is still out on that one. Other butterflies, including the Peacock, are also parasitised by this fly but their numbers do not seem to have been so badly affected, probably to do with the timing of their life cycles.

Things to do this month include :
• Rock Pool Rummaging – West Runton beach.
• Children’s Wildlife Watch and Nature Walks – Hickling Broad.
• Beginners Guide to Butterflies – the Priory Centre, Great Yarmouth.
• Autumn Passage Birds – Cley Marshes.
For details – or 01603 625540.
• Guided Walks – Titchwell Nature Reserve – 01485 210779.

© Sheila Sims 2013