A green-eyed dragon at Platt Bridge

I was excited and intrigued to get news yesterday of at least two Norfolk hawkers at Amberswood LNR, Platt Bridge. Excited because this is a rare species in the UK which historically is known from just a few sites in East Anglia and it's a species that I had never seen previously. But what's it doing in Greater Manchester? Surely the dragonfly is called Norfolk hawker for a reason?

I suppose that on occasion given the right climatic conditions a few individuals might reach the UK from the continent and at such times they could appear anywhere, though surely the south and east coast would be most likely, or at least somewhere on the coast, not 30km inland in North West England.  

Many species of odonata have spread north in the UK in recent years due to climate change and there have been several additions to the UK list. The presence of Norfolk hawker at Amberswood may just be another example of this, and if so we may need to adopt it's other name, green-eyed hawker.

The reason for my intrigue was that one was reported here last year as well, in fact I came looking for it but didn't see it. Amazingly there was also a sighting from the year before that as well, making this the third consecutive year that Norfolk hawker has been seen at this site. Surely this can't all be coincidence, surely they can't all be vagrants that just happened to turn up at Amberswood for three consecutive years? Perhaps the most likely scenario is that the species might actually be breeding here following a previous influx?  

However, this is where it gets a bit complicated. The UK population of Norfolk hawker is almost completely tied to the aquatic plant water-soldier Stratiotes aloides which is crucial to egg laying (British Dragonfly Society). To the best of my knowledge there is no water-soldier at Amberswood, and in fact as a native species it's a rare plant which is on the Vascular Plant Red Data List, and is largely confined to central and eastern England. It does however occur as a more widespread garden escape in places (The Wildlife Trusts), though I must say that I don't recall seeing it anywhere in North West England, let alone Amberswood. So if these dragonflies originated from the UK population then in all likelihood they would not be able to breed because of the lack of water-soldier.

Strangely though, European populations of green-eyed/Norfolk hawker are not so tied to this plant, so if Europe is the source of these dragonflies, which it most probably is, then in theory the absence of water-soldier may not be an issue. However, what is not clear to me is why the UK and European populations differ in this way. Perhaps there are other aquatic plants in Europe which the dragonfly can use, but these plants might be absent from the UK leaving them with just water-soldier. 

An interesting thought is that in places where water-soldier does occur as a garden escape, it can become the dominant species and a nuisance and as such is often removed as a conservation measure. However, Norfolk hawker is a legally protected species and if breeding is suspected at a site such as Amberswood then in order to remove water-soldier a license would be required, because removal of the plant could negatively impact the dragonfly.

So Norfolk hawker appears to need more than just climate change in order to spread, it seems that it may also need the presence of a garden escape to help it and also the understanding of conservation managers.

Today the dragonfly was generally elusive, I only saw it landed once in nearly three hours and often it would go missing for 30 minutes. The photo above shows a typical view of it hawking over a glade, easily identifiable even in flight by it's clear wings, smallish size and brown body. Brown hawker which is superficially similar has an orange sheen to it's wings and is quite a lot bigger.

Interestingly I saw a photo that was taken this morning of Norfolk hawker at the site, which clearly shows damage to the lower edge of both hindwings. This damage is not evident in my photo which obviously proves the presence of at least two individuals. 

The habitat favoured by Norfolk hawker at Amberswood, showing emergent mare's-tail.

 Mare's-tail.

During the time that I was present today, the Norfolk hawker spent most of it's time feeding over this glade, often at tree height and occasionally landing high up and always out of view.

There were plenty of other dragonflies at the site, including brown hawkers, southern hawkers, emperor, common darter and black-tailed skimmer (above).

Also at least three species of damselfly including these red-eyed damselflies which are in the wheel position.