Sunday, 25 June 2017

Local dragonflies (2)

It ended up being Tainan again Sunday, albeit the more far-flung destination of Dong Shan higher up in the mountains. The hoped-for and expected clubtails proved easy to find now that this area is wet, and my chief target among them was the tiny Horn-tailed Clubtail Stylogomphus shirozui. There were just a couple on a rocky stream next to the road, but they really were quite confiding.

The larger and more numerous Brook Clubtail Leptogomphus sauteri was also easy to pick up on this same small stretch of stream, with somewhat surprisingly the majority of individuals present being females (all busily laying eggs in the relative comfort of just the one attendant male). As generally speaking I do not encounter many clubtails in Tainan County, I had to take the opportunity to fill my boots with these, too, while they were there for the taking.

More unexpected were the two big dragonflies that were working the same area: a female Tiger Hawker Polycanthagyna erythromelas and a Brown-winged Goldenring Chlorogomphus risi. The Hawker had been buzzing around all morning, and was seemingly unwilling to land. Unfortunately, it did so without my noticing it, and I flushed the laying female on my way to the Brown-winged Goldenring which I had spotted busily laying in the same tiny puddle! Fortunately, I did come away with a record shot of the latter, perhaps the more difficult of the two to photograph anyway.

The usual small stuff was also well-represented on this tiny stream, with Formosan Piedwing Psolodesmus mandarinus and Yellow-tailed Forest Damsel Coeliccia flavicauda both being well worth snapping. The Red-legged Flatwings Rhipidolestes aculeatus of earlier in the year were nowhere to be found, and it seems as though their season is now finished at this site for this year.

It really is a very pleasant spot Dong Shan, and it's nice to have somewhere 'on the doorstep' to go where all this wonderful diversity can be easily found. Above photos taken at Dong Shan, Tainan County 25/6/17.

Saturday, 24 June 2017

Local dragonflies (1)

Absent much in the way of birds, only dragonflies remain, but there are sufficient in their ranks to keep me interested. I wanted more Dog-legged Clubtails Burmagomphus vermicularis this week anyway, so returned to the stream at Xin Hua for them in the morning on Thursday. There were two on a mere ten-metre stretch of stream, with doubtless many others now along the unchecked parts, so they now go down as 'easy to find' following the torrential rains of last week.

Also following the torrential rains of last week, a seasonal pool further along the road in Zuo Zhen held a quite astonishing variety of dragonflies, with one or two choice targets in their number. Chief among these was a pair of Amber-winged Gliders Hydrobasileus croceus, a species I have only seen once before in the south and was obviously keen to photograph. As this species is one which is constantly on the wing, it is a big challenge to shoot; too big a challenge for me, as it turned out, and I would fail completely with it in the heat of Thursday. A return to the same pool Saturday did at least result in a record shot, not the best I've ever managed of dragonfly species!

There was a remarkable twenty species of dragonfly on and around this small pool Saturday morning, and most were much more amenable to having their photo taken than were the gliders! Perhaps best among them were the Island Emperors Anax panybeus, another one which usually does not stop, but which did at least elect to both hover and lay on occasion this morning.

Of greater interest locally perhaps were the Scalloped Spreadwings Platylestes praemorsus and Pied Sapphire Flutterers Rhyothemis regia, both of which are much more localised in terms of their national distribution than any of the other species present. The flutterer in particular has to be one of the most attractive species of dragonfly to occur on the island.

Once again, it was far too hot to extend my search much beyond mid-morning, so I made do with what I had on my camera from this small pool and that was it. Hopefully, the next batch of dragonfly photos will come from somewhere slightly further afield than Tainan! Above photos taken in Xin Hua and Zuo Zhen, Tainan County 22-24/6/17.

Friday, 23 June 2017

Greater Crested Terns

I really do get stuck for places to go once the migration is over and (ironically, as it affords me a greater amount of free time) work begins tailing off for the summer. The Qi Gu sandbar holds a few terns, but all now are Greater Crested Thalasseus bergii. Most are first-summers, so non-breeders, though a few adult or 'adult-like' individuals continue to linger. Despite a few of the locals telling me that the youngest-looking of these are 'this year's' on account of high-pitched calls and occasional begging, one look at the long-replaced (yet very worn) mantle and scapulars shows this not to be the case. Moreover (and more interestingly), there are staringly obvious moult limits in their primaries, and a closer look at these feathers reveals something really quite interesting: Some of these birds have up to three generations of feathers present in their primaries, indicating that they are at least one complete moult cycle past juvenile! The first individual below is an excellent example of this, as it has new P1-2 (and covert) and dropped P3, with P4-8 'old' (from a complete post-juvenile moult, which I did not realise Greater Crested Tern had), P9 dropped and in the process of being replaced (as a continuation of the post-juvenile moult), and P10 still juvenile.

Despite some retained orange in the legs (a feature of juveniles), this second bird (below) is more advanced than the first, with all juvenile primaries having been replaced (though P10 is still growing, as part of the post-juvenile moult) and P1-3 new and contrasting with the rest of the wing. So again (and surprisingly for me at least), two moult cycles evident in the one wing!

I had expected that, like the big gulls that winter here, adult Greater Crested Terns would complete their primary moults in their winter quarters and, once done, would then (and only then) head north to breed. However, there has been a surprise (for me at least) here too, as it turns out that only a handful of inner primaries are actually replaced over the winter months and moult is then suspended for the entire period of courtship and breeding. I only snapped two adults this week, and both show the same differences between silvery inner primaries and darker-tipped outers as do the first-summers above. The first individual (below) shows silvery feathers P1-5 and the second P1-6. The individual with the fish is from an earlier post, and shows silvery P1-4. As the number of pale inner primaries varies from individual to individual, the contrast between silvery inners and dark-tipped outers is one created by moult rather than by plumage (it is that of old feather versus new). As no adults in active primary moult occur at this time, it looks as though primary moult in Greater Crested Tern is suspended for the breeding period rather than completed before it. 

The first-summers (with their newly-replaced inner primaries) are arguably at the same stage of feather replacement in respect of these feathers as are the adults (or, alternatively, in the same 'pattern' as the adults), though all retain traces of juvenile plumage. I hadn't realised that feather replacement in Greater Crested Tern proceeded in this fashion (i.e. moult gets suspended for breeding), an embarrassing revelation after having looked at so many! It does at least go to show that there's always plenty to be learnt, regardless of how uninteresting and tedious a day might otherwise appear to be! Above photos taken in Qi Gu, Tainan County 5-6/2017.

Friday, 9 June 2017

Dog-legged Clubtail

I was hoping for more than one Dog-legged Clubtail Burmagomphus vermicularis on my small stream at Xin Hua Friday morning, but one was all I got. A second recently emerged individual I turned my back on as I put my bag down had disappeared when I turned round to face it again. Still, there were rather many Black Riverdarters Onychothemis tonkinensis around to play with this morning, and I was happy enough with these as they are pretty striking dragonflies. Of course, there were numerous obligatory Lineated Orange Jewels Libellago lineata along the river also.

By late morning, the heat had become absolutely unbearable, and walking just a few metres in it left me sweating and knackered; thus it was time to call it a day! Above photos taken in Xin Hua, Tainan County 9/6/17.