Tuesday, 19 September 2006

Dragonfly gives me the once over

It is quite a strange feeling to be given the once over by a dragonfly. On one very warm afternoon last week this is exactly what happened. A dragonfly, about seven centimetres in length, approached me with a very direct flight and hovered just in front of my face. After a brief moment it adjusted its position, viewing me from a slightly different angle before turning and moving away to continue its patrol. As it turned I could see the paired spots, one large pair on each segment of the elongated abdomen. Most of the spots were a pale leaf green in colour. Those on the last three segments were pale blue and the last two pairs of these were each fused into a single larger spot, all characteristic features of a male southern hawker dragonfly. This is an inquisitive species that patrols low down around its favoured small, shaded pools and ponds. As such, it is often common in wooded areas and in urban gardens, where cats frequently catch it.

This was not the only species of hawker that I have seen in recent days. The similar, though somewhat smaller, migrant hawker has been much in evidence, patrolling over local ponds and getting caught in our mist nets, used to catch swallows on the local fen. The male migrant hawker also sports paired spots, though his are pale blue along the full length of the abdomen and all remain unfused. A yellow wedge, shaped like a golf tee, appears in the middle of the second abdominal segment, a feature absent in our other hawkers and useful when dragonfly watching. Migrant hawkers appear to be less inquisitive than their larger relative, patrolling low only around breeding ponds and preferring to search for food up along the edge of trees and hedgerows. As its name suggests, the migrant hawker is, to some extent, a summer visitor, with large numbers reinforcing our resident breeding population.

These two ‘blue-green’ hawkers are joined in Britain by another ‘blue-green’ species: the common hawker, which, despite its name, is anything but common within Norfolk, being restricted to a few localised sites in the east of the county. There are also two brown-coloured hawkers to be found in Norfolk, one of which, the Norfolk Hawker, is not found anywhere else in Britain. With its brilliant green eyes, this striking beast is well worth looking for in spring around the Broads. Any brown-coloured hawkers seen on the wing at this time of the year will be a brown hawker, a more widespread species. A number of related species may turn up in the county as vagrants and, with global warming, some of these may yet become established.

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