Tuesday 2 October 2018

Great Frigatebirds

I've twice bumped into frigatebirds in Japan and though neither were close enough to identify to species that never stopped me adding frigatebird sp to my Japan list. So, I'm now in the position where these Great Frigatebirds aren't numerically a japan tick but they are a lifer. Oddly enough I have a frigatebird sp on my British list too, from way back in the 70's. I don't have any other birds ticked when unidentified to species which I suppose shows how rare frigatebirds are in temperate waters while nevertheless being instantly recognisable as a family.

These particular birds have been hanging round Katagai harbour in Chiba for a couple of weeks, even longer in the general area I believe, but last Tuesday through Thursday was the first time I've had more than one consecutive day off during their stay and as it's a bit far for a one-day dash I've been hoping they hang on till I was free. I finished work at 9pm last Monday and by the time I got home and prepared for the trip I didn't get away until 11pm.

Much to my relief the weather people had informed me there would be continuous rain on Tuesday, so, nothing to worry about then. It actually poured down for about 30 minutes as I was approaching Katagai and but there wasn't another drop until I was leaving about six hours later. Still, it was very heavily overcast and anything but ideal for photography which is a pity considering how photogenic these amazing birds are. I arrived at the harbour around 8am and though I didn't know exactly where to look for them it didn't matter because they're pretty hard to miss. Even the weather people couldn't have messed that up. Probably couldn't... possibly. The (much) larger of the two birds was flying around when I arrived, getting a post downpour blow-dry perhaps, while the other sat hunched on its favourite perch looking miserably bedraggled and totally out of place in the dank, dripping, colourless morning and the rather flat and featureless (dare I say desolate) setting they'd adopted as home.

There were many a mid-winter day's I'd spend birding along the bleak north east coast of England when you knew the depressing half light was as good as it was going to get before the sun gave up and sank again. I'm not knocking the north east of England by the way, it's stunningly beautiful most of the time, but there is a certain winter light that weighs very heavily and makes summer seem like a false memory. That same light was lurking in Katagai that morning.

The freshly bathed dog look.

As I mentioned the light was abysmal all day until a brief spell of just a few minutes in the afternoon when the light quality improved and before the rain finally set in. I could get a couple of shots of the birds perched that actually showed colour. Even the antenna had colour!

Don't be fooled, it isn't sunny but this is the best it gets light-wise.

There was a huge difference in size between these birds so I'm assuming they are male, possibly small male, and female, possibly large female and that's how I'll refer to them; I have no idea how large a difference there normally is between the sexes. However, if the size relationship had been reversed I might have wondered whether these birds could have been Great and Christmas Island Frigatebirds. The fact that Christmas Island is significantly larger than Great rules out any chance of that being the case but it also illustrates, to me at least, how difficult it would be to identify a non-classic juvenile at sea, or just a lone bird for that matter.

According to the David James paper in BirdingASIA (vol#1, 2004) Christmas Is is the longest- and Lesser the shortest-billed of the Asian trio. The small bird in Katagai had a very long looking bill, easily more than double the head length compared to the larger bird whose bill was clearly less than double the head length. This is somewhat surprising because females are supposed to be longer-billed than males. According to James, another feature suggestive of Christmas Island is the extremely white ulnar bar, but it isn't too difficult to find images of Great online which also have strikingly white forewings. Finally the distribution of white on the underparts, though far from classic Christmas, it certainly isn't an obvious fit for Great either. At least not compared to the larger of the two birds here which looks a classic juvenile Great.

The first 10 minutes I was there saw the larger of the two trying to land on the antenna and the smaller of the two trying to deter it. Eventually it made the sensible decision to land on the antenna support but even that was was full of drama.

Pass after pass the female tried to land next to the male, who wasn't having any of it. 

Finally it managed to land on the support, teetered along flapping wildly before falling off and remaining suspended by its wings for a moment.

The importance of assessing the belly patch from below is often mentioned because the viewing angle can affect the interpretation of the shape but it seems that feathers can also move slightly which may affect the shape of the patch. One more reason to hope your flyby juvenile frigatebird is a classic.

The female has a standard egg-shaped Great belly patch.

Viewed more from the side, still with a compact belly patch.

The following two shots of the bird's right side suggest slight feather displacement can affect the overall impression of the patch shape.

The male also shows an egg-shaped belly patch but has distinct spurs. They emanate from far too far back to suggest Lesser Frigatebird but that a single row of white sub-humerals produces a narrow forward-angled spur seems at odds with the classic Great patch shape as I understand it. Compared to the previous image, the bill of this bird is extremely long.

A more side-on view of the spur.

The upperwing coverts are strikingly paler on the male but it seems all the species can show equally white coverts created by the broader fringes.

The female with an obvious but unspectacular pale ulnar bar.

The male with outstanding white in the coverts.

A closer view of the coverts shows most lessers (and outwardly the marginals) have dark shaft streaks in otherwise white feathers.

The female's coverts are brown with neat brownish-white fringes.

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