Saturday 3 December 2016

Great White Egret... a flock of alba!

It's good to know there are some constants in life. There was a time, long long ago, when I didn't have any idea of the status of alba Great White Egrets in Japan. I never saw one. It wasn't until I was taking an Aussie birder around Lake Biwa six years ago and he asked "What are those egrets?" that I connected with my first. Those egrets were both Great White but due to the striking size difference they could easily have been two species.

I saw another that winter then others irregularly during subsequent winters. I probably see two to four per winter nowadays and increasingly I feel able to pick out lone birds on size rather than looking for yellow in the legs. It sounds like I've got my eye in now, doesn't it? Well, I thought so until yesterday when I came across a flock of 42 plus a few others later in the day. I like, or liked, to think that I was always keeping an eye out for alba, and had a reasonable notion of their status in this part of Japan. It seems I still don't have any idea of the status of alba Great White Egrets in Japan - or I ought to say in Kansai.

Is Mie a hot-spot for them or have I just not paid sufficient attention to Great Whites when I go there? The latter is possible because there's always so much else to look at. I only remember seeing one there, a spring bird coming into breeding condition, could I really have been missing so many for so long?

The Birds of Japan (Brazil 1990) gives the status of alba as a 'casual winter visitor' to Japan. Whereas the more recent Birds of East Asia states "Winters increasingly from Hokkaido south, but mainly from C Honshu to Kyushu..." So maybe there is a real increase in the number of birds wintering and it isn't simply that I was missing them until six years ago. I like to think that's the case. Nevertheless a flock of 42, that's some increase!

Is there any surprise I've been able to pick up lone birds purely on size difference? I think not, take a look at the comparisons below.

Part of the alba flock, note the single modesta (left at the back) looking as though it could be Intermediate compared to the other birds. 

The alba body looks similar in bulk to Grey Heron but the neck is slightly longer (and thinner) and the legs appear longer too giving it a slightly larger appearance overall, modesta on the other hand is slightly but distinctly smaller than Grey Heron. The slimmer head and long bill of alba also add to larger appearance. The modesta is at the rear in this shot; it seemed it couldn't drive the flock off its lagoon so keeping them contained was the next best option.

The extent of yellow on alba legs is variable, sometimes just a narrow stripe on the inside of the tibia, at the other extreme most of the legs and even feet can be yellow. Modesta is usually black-legged but the upper tibia can be a 'colourless' grey in non-breeding condition.  

I've never seen so many yellow legs in one place; more than a year's quota just in this shot.

There were two interesting things going on with this flock, other than the fact that the flock even exists, one was the behaviour of the single modesta towards these 'interlopers' and the other was interaction between the alba reminding me of dancing cranes. 

Local (modesta) egrets can be quite territorial away from roost sites and they often expect a whole small lagoon or ditch to themselves. The modesta on this lagoon was doing his best to police an impossible situation, my interpretation was that it couldn't chase off the entire flock so it was trying to keep them contained in one corner. Whenever one of the alba began walking out of the 'containment zone' the modesta would fly at it giving the usual deep almost staccato growl.

An alba (foreground) pushing the bounds of toleration, whether it knows it or not.

Chasing alba...

and another...

In this shot, though not others, the modesta seems to have a hint of bluish at the top of the tibia. Maybe breeding hormones are kicking in already which could account for its aggression.

and they just keep on coming...

This alba got lucky, another modesta dropped in and that got the full get-off-my-lagoon treatment.

Then back to containment... what a long day this must have been.

A hint of bluish tibiae again here...

Then there were the dancing cra... er egrets...

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