Friday, 15 August 2014

Birds, Bats, Bugs & Butterflies

The Mid-Summer Lull? What’s that? The few weeks between the two main migration periods can be a quiet time for birders, but not if you’re into other forms of natural history. It’s been a few weeks now since my last post but plenty has been happening!

Rarest bird I've seen recently has been a BLACK-WINGED PRATINCOLE on the Ouse Washes. This bird has been tracked down the east coast and everywhere it has been erratic and unpredictable in its appearances. So too in Cambs, and it was only on my second attempt that I saw it. I waived the 5 mile round walk in favour of a 50 yard one to and from my viewpoint on the other side of the washes. It was more distant, but all the features were visible.
BLACK-WINGED STILTS have had an incredible year with successful breeding at multiple sites. One was just half an hour from home (assuming this was the actual breeding site, must try to find out) so after the first pratincole attempt I dodged the thunderstorms and headed to Cavenham Heath where I saw the whole stilt family – both parents and 4 juveniles. Awesome stuff.
Two of Britain’s most elusive birds breed in Cambs and I was lucky enough to see both this summer. Singing quail regularly occur within a few miles of my home, but I’ve never seen them, until this year! Persistence paid off with sightings of 2 different individuals (one was actually in Herts). Corncrakes are also shy and retiring but I joined a trapping session at the Nene Washes with the RSPB and we got lucky. We spent 2.5 hrs working a stretch of overgrown bank making lots of noise and eventually herded no less than 8 into the traps. The best catch this year apparently and half were wild born birds – a single juvenile and a female with 2 chicks, the latter 2nd generation wild corncrakes. With the releases now over, they’re on their own, but it’s great to see successful breeding taking place.
common quail

I joined a couple of harp trapping sessions and among the selection of pips and Daubenton's were a couple of rarer bats – a female whiskered and a well-hung male NATHUSIUS'S PIPISTRELLE. The latter species is the subject of a national survey this year. Though it was only discovered in Britain in the nineties it is now thought to be so widespread it has been recorded from almost every English county and has an affinity for large water bodies. It is a migrant, probably most numerous in the autumn but there appear to be resident populations too and some which hibernate here which may have travelled from the continent. A recent ringing recovery of a Somerset-rung Nathusius' was made in Holland! This particular bat had very large swollen 'bits' so was in prime breeding condition. The bat regulars got rather excited by his inflated genitalia – oo er, missus! 
whiskered bat enjoying the joke we'd just told it

Nathusius's pipistrelle
I rarely show too much interest in anything smaller than a butterfly but a few interesting bugs caught my attention during the period. One is a tiny mayfly, not more than a few mm long, which landed on my hand one evening while I was watching the stilts at Cavenham. I fancied it might be something new to science and thought about naming it Hanlon's Flying Fish Mayflything – see the resemblance from the photo? (to a flying fish, not to me). It turned out to be Caenis horaria, certainly a little beast I've never noticed before!
Violet ground beetle

golden-bloomed grey longhorn Agapanthia villosoviridescens

Caenis horaria (photo by Lee Gregory)
Since last year strange things have been happening in the butterfly world. There has been a remarkable influx of long-tailed blues (some staying to breed) and this year a colony of maps were discovered in Dorset. A meadow fritillary was recently seen near Milton Keynes and gorganus (Continental) swallowtails invaded the south coast in 2014 and also appear to have bred. Many of these are likely to be the result of releases from captivity but not all. The highlight for many has been an unprecedented influx of (undoubtedly wild) SCARCE or YELLOW-LEGGED TORTOISESHELLS, continental butterflies which recently colonised Finland and have only been recorded in the UK once previously. They appeared this year for the first time in Holland, in their hundreds. After reading about this I suddenly remembered seeing a couple of reports of large tortoiseshells in East Anglia earlier in the day and remembering they were very similar in appearance I tweeted the staff at Minsmere raising the possibility that their 'large tort' might be something rarer! The following day they checked photos and saw the butterfly again – it was a scarce! More east coast sightings followed but the Minsmere individual had disappeared by the following day when I headed up to Breydon for the great knot. The wader it turned out had departed and I found myself just short of Norwich wondering where to go.
As it turned out I was just 10 miles from Costessey, where another of this species had been identified the previous day. But being just 2 miles from the site of a mass release of butterflies during a funeral the previous week, the possibility of a wild origin had been 'written off' by many, including me. But with more turning up around the coast it started to dawn on me that the release may have just been a coincidence.
I headed to Costessey and after an hour or so of searching, relocated the tortoiseshell, which proceeded to sit up on a tree trunk for the best part of an hour. A few locals managed to twitch it and it was eventually seen by around 50 people, most of which had turned up on spec hoping for a sighting. It would have been seen by more had the butterfly stuck around but it soon headed off towards the large pond nearby and despite further searching, was never seen again. For now the sightings of scarce torts has died down but I don't think this is the last we'll see of this species in the UK.
scarce tortoiseshell

scarce tortoiseshell

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