Friday, 7 June 2013

Norfolk Hawker

My own rubbish photo from 2011.
In 2011 a Norfolk Hawker dragonfly was sighted at the Hayling Pit by Steve Brooks from the London Natural History Museum, well outside of its known range in Norfolk and Suffolk. It chose to hold a territory over a dense patch of water soldier plants, at the allotment end of the pit. Less surprisingly, this is just the kind of place they would be found in the Norfolk Broads, for example. The big surprise is that it should make such a giant leap beyond its normal range. The attraction must be the water soldier, which is a Broads speciality but was probably deliberately introduced into the Hayling Pit. 

We all enjoyed watching and photographing that first dragonfly holding a territory, but it kept battling with other dragonflies and there was no sign of a mate. In 2012, I am aware of only one sighting, on Rudd Pit.

This week, there has been a sighting of the first Norfolk Hawker in Bedfordshire, at Potton Wood. Did it originate from Little Paxton? We will never really know, but a good indicator would be to look for the dry, shed skins of the nymphal stage that emerging dragonflies leave behind. These are called 'exuviae'.

Ian Dawson lives very close to the reserve and he has conducted surveys of spiders and other invertebrates on the site over the the years. He also takes part in our breeding bird surveys. Here is what he wrote today:

"I took my scope this morning and 'digiscoped' some of the hawker-type 
exuviae on the Water Soldier in the NW corner of Hayling Lake, Paxton 
Pits (TL191624), then returned with a Heath-Robinson contraption (a 
plastic fruit punnet attached to the end of a telescopic pole) to try to 
reach those closest to the shore. In the end I succeeded in collecting 
six. Two Emperors were emerging and I managed to convince myself in the 
field that all six exuviae were Emperors. I was out the rest of the 
afternoon and evening, so was unable to check them properly until now, 
but comparison with the life-size silhouettes in Steve's book 
immediately showed they were too small for Emperor, and checking the key 
features revealed that all appeared to be Norfolk Hawkers: 5 male and 1 
female!! As far as I know there have been no sightings yet this year of 
any adults at Paxton Pits, but it seems highly likely that the Potton 
Wood individual came from Paxton".

"I counted at least 30 large dragonfly exuviae on the Water Soldier 
today: some of these were certainly Emperor, but I doubt that the only 
six within reach of the shore were the only Norfolk Hawkers. The site 
manager confirmed today that they will be able to take me out in a boat 
next Wednesday to collect more exuviae, so that should give a better 
indication of the extent of the breeding area".

It would be lovely to see some photos of these big brown dragonflies taken at Paxton Pits. Go and have a look for yourself.