We don't get to see too much in the way of dragonfly action in a normal year on Bardsey. The fresh water areas on the island are eutrophic in nature, and whilst this favours the abundant Palmate Newt, it means that only Blue-Tailed Damselfly breed here with any regularity. So while we were traversing the north-west coast of Scotland, we went on a Dragonfly hunt!

This impressive male Golden-ringed Dragonfly was hanging out in a bog near Loch Morar (which incidentally is the deepest freshwater body in the British Isles with a maximum depth of over 1,000ft). Females have a distinctive 'spiked' vulvar scale, diagnostic of the genus, which aids in the oviposition of eggs in streams and ditches. The larvae of this species live for 3-7 years before emerging as adult dragonflies. (c) Richard Brown

Keeled Skimmers were abundant in the same bog, with multiple females egg-laying in the shallow ditches. The smart males, such as this one, were duelling it out over the prime stretches. Keeled Skimmers are common in Southern Europe, but only locally common in Western Britain and Ireland. (c) Richard Brown.

Perhaps the most confiding of all the Dragonflies on the bog was this female Northern Emerald (thanks Andrew!). Although not very visible in this photograph, the two large yellow spots on the third abdominal segment and a broader waist readily separate it from the male of this species. In the UK it is confined to north-west Scotland. (C) Giselle Eagle

Keeping the emerald theme going, this time with a smart male Common Emerald Damselfly that we encountered in another bog on Muck. Males are separated from females by a number of features. Eye colour is blue in males but dark in females. Males show a blue pruinosity (a waxy colouring which develops as the damselfly matures and covers the underlying colouration) which covers all of Segment 2 (which also helps to separate it from the the more southerly Scare Emerald Damselfly), and blue S9/S10 with a distinctively shaped abdomen tip. All Emerald Damselfies share the characteristic 'spread' wings at rest, with all others holding their wings closed. (c) Richard Brown

This probable Highland Darter Sympetrum (striolatum) nigrescens was basking on stones near the bog. Some publications question its validity as a separate species suggesting that it is just a melanistic form of Common Darter S.striolatum. Either way, the lack of yellowish streaks on the femora and the dark sides to the thorax, coupled with large amounts of black around the edges of the eyes and the blackish underside to the abdomen, suggest that this is of the highland form. Interestingly, early odonatologists suggested that Highland Darters were the product of hybridisation of Common Darter and Black Darter and this continues to be a long-standing debate. Recent genetic studies have shown some evidence of isolation from Common Darter, especially on Scottish Islands, resulting in restricted gene flow. It is still suggested, however, that Highland Darter is merely a northern morph of Common Darter. (c) Richard Brown.

And finally a straight-forward, no-nonsense, Large Red Damselfly. Exactly what it says on the tin. (c) Richard Brown.

I thought Rich needed a rest from his Greenish Warbler research, so I booked a holiday in a yurt on the Isle of Muck for the last week of our holiday. It was phenomenal! Corncrakes crexing from the meadows were the avian highlight, although we did see Twite, which was new for the yearlist. The mega highlights of the holiday, however, all came from the depths of the sea...

On our first day trekking around an island only slightly bigger than Bardsey, we got some distant views of two Basking Sharks feeding in the waters in front of the Isle of Eigg. We watched them for half an hour or so before heading on - there was still a lot of coastline to explore! We hoped we'd get closer views. A couple of days later, we spotted another Basking Shark, very close in to shore. The only problem was we were viewing it from Beinn Airein - the highest point on the island. We made a hurried descent to the bay and watched the shark feeding close in for a couple of hours! Brilliant! Then, on our last night as we enjoyed a few ciders, a Basking Shark appeared in the bay opposite the yurt.

Adult Gannet, Great Black-backed Gull and Shag to give this enormous sea-beast some scale. This particular shark seemed to be around 12ft long, which is big enough, but massively shorter than the largest specimen ever reported, which was trapped in a herring net in the Bay of Fundy, Canada in 1851 and measured in at a whopping 40ft and tipped the scales at an impressive 19 tonnes! Sadly, the commercial value of Basking Sharks as food, animal feed and sharks liver oil (not to mention the appalling trade in sharks fin) has resulted in over-exploitation of this species and so long-lived individuals like the 1851 specimen are rarely recorded now. Basking sharks filter-feed on blooms of plankton, small fish and invertebrates in the water column and can get through as much as 1800 tonnes of water an hour. (c) Richard Brown

Sea-beast the Second! After the excitement of the Basking Shark, came the excitement of the elusive Otter. Yet again the yurt was the place to be and we watched this large individual catching fish just offshore. It's no surprise that he was busy eating, British Otters need to consume somewhere in the region of 15% of their body weight per day to enable them to survive in our chilly waters. (c) Richard Brown

A somewhat distant Minke Whale which didn't quite make it onto the yurt list. The Minke Whale is apparently named after Miencke, a Norwegian Whaler who became the butt of his crewmates' jokes when he repeatedly harpooned this species thinking that it was the much larger Blue Whale. They crew dubbed this smallest rorqual whale 'Miencke's Whale' and the name eventually stuck. (c) Richard Brown

The yurt overlooking the much larger Isle of Rùm where several tens of thousands of pairs of Manx Shearwater breed high up in the Cuillin Hills. Which goes some way to explaining their constant presence in the waters around Muck. It seems a few pairs have started to breed on Muck but, as on Rùm, the presence of non-native rats will not be helping their productivity. (c) Richard Brown

So we're now back on Bardsey, and just in time. It might only be the last week in July but autumn is well and truly under way. Over 100 Willow Warblers have been logged for the last two days, predominantly birds of the year, along with the first few Sedge Warblers and Grasshopper Warblers heading South. Up to 13 species of wader have been around the coast and Swifts are screaming their way South. 

The first Grasshopper Warbler of the autumn was predictably a nice fresh bird of the year. Little is known about Grasshopper Warbler migration but it is likely that this smart Locustella will visit important refuelling sites in Portugal before reaching its wintering grounds in North Africa. (c) Richard Brown

We've been given a few more pointers on the separation of Greenish Warbler and (Bright) Green Warbler. It's not going to help to secure the identification of our bird, but it does provide a few more talking points. The reason that Green Warbler has been suggested is due to the extent of yellow in the supercilium and ear coverts, which seems to be on the extreme side for Greenish Warbler, however see: http://birdsofkazakhstan.com/greenish-warbler-phylloscopus-trochiloides/ for photographs of Greenish Warbler in South Kazakhstan (but different light conditions). The chin, throat and upper breast have a pale yellow wash in our bird, but this seems to be within the realms of Greenish Warbler.

A new feature to us (and apparently said by some to be diagnostic) is the possibility that the feathering along the lower edge of the eye is white (thus contrasting with the ear coverts) in Greenish Warbler and matches the colour of the ear coverts in Green Warbler. It is important that this is assessed in good light conditions so perhaps we can't look at it with any certainty using these photos. However it seems fair to say that our recent bird has feathering more concolourous with the ear coverts than the other two birds, but perhaps not to the extent expected in Green Warbler? The three photos below are full size so anyone out there who's interested can blow them up a bit bigger for a closer look. The lack of yellow in the wing bar seems to have no relevance as fresh Green Warblers on the Turkish Black Sea Coast can show white wingbars when fresh. Ultimately it seems that some extralimital, worn birds cannot be identified without DNA analysis or a sonogram.

We would be very interested if anyone out there knows about leg colour (which was surprisingly pale in this bird), or the patterning of white on the inner web of the outer tail feather which in this bird was as would be expected in Greenish Warbler.

The Bardsey Green(ish) Warbler (upper photo) clearly differs from our two other recent Greenish Warblers (middle photo 11 June 2010, lower photo 8 June 2012). (c) Richard Brown

Our busman's holiday has continued with a few days of birding, ringing and a quick twitch. The smart male Red-backed Shrike at East Chevington was too close to ignore, so we went to pick it up for the year list and complete the three commoner shrikes hat-trick (watch out Tonk and Aimes, we're getting closer). We had a fantastic day's ringing around Teesmouth with a few wader pulli, including Rich's first Avocet, and fifty plus passerines including lots of Reed Warblers and dispersing juvenile warblers.

The East Chevington Red-backed Shrike was somewhat distant and seemed pretty happy to stay in the large patch of sheltered scrub down to the south of the hides. Considering that it is smaller than a Starling, this voracious carnivore is something of a monster, capable of taking small mammals, reptiles and birds along with its more usual prey of insects. The Germans call them Neuntöter, referring to the superstition that they only feed after they have killed nine creatures. (c) Richard Brown and Giselle Eagle

Avocet and Ringed Plover pulli. Productivity isn't looking too good this year, perhaps due to the attentions of local foxes. (c) Richard Brown

A brief weather window meant that we could get off Bardsey for a 'summer' holiday. The interesting Green(ish) Warbler continues to cause debate, so we intend to continue our research whilst we're off. But today we were constantly distracted by news of the Alpine Swift which was continuing to show well at Buckton Cliffs to the North of Bempton. The forecast was bad, it was already two in the afternoon, but we fancied a drive so headed out for the two hour trip. The forecast was right. We made the mile plus walk to the trig point in something between drizzle and rain. But the bird was still there, feeding low along the cliff edge. It frequently passed just a few feet over head, but it wasn't the best conditions for photography. However it was well worth the drive to spend an hour in the company of this monster Swift which has a wing span of over half a meter.

This cracker has lingered since the 29th of June, the most predictable of the 21 birds to have been reported in the UK so far this year. Alpine Swifts pair for life and return to the same nest site each year, so perhaps this bird isn't an established breeder. But they can also range long distances when looking for food. Whilst the adults are away hunting, the chicks can lower their body temperature to reach a torpid state, thus surviving unattended for long periods. (c) Richard Brown

It has been suggested that we may have dropped a bit of a bollock. More precisely, a few very experienced birders have suggested that yesterday's Greenish Warbler bares more than a passing resemblance to a Green Warbler. This may be partly due to the two photographs we posted yesterday; the last day of June was glaringly sunny so the photos were either in full sun (the two posted), or in the deep shade of the ringing hut (see below). But the heavy appearance of the bill, coupled with yellow tones to the supercilium, have rightly raised a few questions. The bird clearly doesn't show the Wood Warbler-like tones to the mantle and throat which are perhaps the first thing that comes to mind for this recently split species, but perhaps a summer bird wouldn't be as obvious as when in fresh autumn plumage? Yoav Perlman's fantastic blog shows what a classic Green Warbler looks like in June here: http://nubijar.blogspot.co.uk/search/label/Green%20Warbler
but what about a more worn individual?

Our bird was tape lured. As soon as the tape was played the bird responded emphatically with several flybys before soon hitting the net. But it would seem that this means very little. Prior to the split of trochiloides and nitidus, it was suggested by some authorities that the propensity of Green Warbler to respond to Greenish Warbler song was a good reason not to split them! So what about the song itself? Our bird sang frequently. Here it must be pointed out that our experience of singing Greenish Warbler is limited to two previous singing males on Bardsey and an oft played recording said to be of viridanus Greenish. However to our inexperienced ear the song seemed identical, when singing to the tape the phrases matched perfectly. It wasn't the longer song, including buzzy bits, which is meant to be classic Green Warbler. But then apparently the song can sometimes be very close to Greenish. It didn't call so no help there.

In the hand the wing formula was almost identical to the Greenish Warbler trapped earlier in June. That is to say that there were emarginations to the third to sixth primaries (although not as strong on P6) and the longest primary was the fourth. The second primary fell between P7 and P8 on the bird in early June, this bird had P2 closer to P8 (which is possibly more Green Warbler although such a slight difference must fall in the realms of individual variation). The wing was 63mm, which doesn't help much.

So we are left with plumage and structure. The pro-Green Warbler argument would point to the very striking supercilium which has yellow tones, the yellowish cheek and the heavy looking bill (bill measurements overlap considerably between the two species but Green averages heavier). But the (worn) mantle is grey green rather than moss, the (worn) wingbar lacks any yellow tones and the underparts and throat are whitish, although with some very pale yellow. The supercilium reaches the bill as in Greenish but it could be argued that it gets a bit more vague above the bill, as in Green Warbler. The legs were surprisingly pale, but we can't find much reference to leg colour other than that Greenish Warblers sometimes have paler legs than normal.

The top photo is of the same bird in the shade. To us it still seems to fit Greenish, albeit a bright individual, and the song must clinch it. But this is the perfect opportunity for everyone with lots more experience than us to tell us we're wrong! We'd love to hear any comments. The lower two photos are of our other two recent Greenish Warblers for a direct comparison (but beware very different lighting conditions). (c) Richard Brown