Wednesday, April 22, 2009

Hong Kong: A Day at Mai Po

There is no question that the premier birding site in Hong Kong - indeed, one of the finest and most famous sites in the world - is Mai Po. The Mai Po Marshes and the nearby shores of Deep Bay are vital staging areas for migratory birds, including the increasingly rare Black-faced Spoonbill (Platalea minor) and thousands of shorebirds. Any naturalist in Hong Kong wants to get to Mai Po, even if (like me) they have been there before (in my case, in 1992).

However, you can't just go to Mai Po. The site is managed and carefully controlled by WWF-Hong Kong. Access is limited, and if you don't go on an organized outing you have to submit a form - only available to visiting naturalists - well in advance (see http://www.wwf.org.hk/eng/maipo/publicvisit/. I was late in getting my form in, so many thanks to WWF-HK for bending the rules a bit on my behalf!

Anyway, I spent a whole day wandering around Mai Po on Monday March 23, the only other visitors being a few parties of high school students on excursion. After my thanks above, it may be churlish to say that from a birding point of view the trip was a disappointment; there were no land bird migrants about, and the vast majority of waterbirds kept themselves at an unidentifiable distance far out over the mud flats on Deep Bay (I was the victim of unfriendly tide tables).

Nonetheless, you don't have to be swamped with rare birds (if you'll pardon the expression) to find delight in a day at Mai Po. After the bustle of Hong Kong it is a place of stillness and quiet, and there is still a great deal to see.

Mai Po is in two main sections. The most accessible is a series of enclosed ponds, or gei wai, established long ago for traditional shrimp farming and still used, under the eye of wetland managers, for that purpose. They are popular with egrets and other water birds, including the Great Egret (Egretta alba) above - a black-billed, black-legged, breeding-plumage bird that looks quite unlike the Great Egrets I am familiar with from other parts of the world.

Little Egrets (Egretta garzetta) were abundant in the gei wai...

...and there were a few Intermediate Egrets (Egretta intermedia) about, including this lone bird in a pond full of Black-winged Stilts (Himantopus himantopus).

Stilts are beautiful, if aggressively noisy, birds! Mai Po is also a site for raptor migration, but most of the raptors I identified were Black Kites (Milvus migrans), abundant residents in Hong Kong. The only exceptions were some very distant eagles (?) on Deep Bay, and the two birds in the much enlarged and enhanced photo above. I think, based on what appears to be a broad dark bar on the underwing, that these are Bonelli's Eagles (Hieraaetus fasciatus); compare my poor shot with the much better photo at http://orientalbirdimages.org/search.php?action=searchresult&Bird_ID=897.

Birds, of course, are not the only creatures that fly at Mai Po. This dragonfly is, I believe, an Asian Amberwing (Brachythemis contaminata - Libellulidae), presumably a female.

And this beauty is a Variegated Flutterer (Rhyothemis variegata - Libellulidae), certainly one of the most striking dragonflies I have seen, and a very common animal at Mai Po.

It took me a while to realize that this stunning insect, common at Mai Po wherever there were mangroves, was a moth and not a butterfly. It is easy to see in flight, but it seems always to land on the underside of a leaf where it can be surprisingly hard to spot. It turns out to be Dysphania militaris, one of the False Tiger Moths in the family Geometridae. I'm not too sure what is false about it, but the bold stripes on the abdomen certainly justify the tiger part!

Back to the birds -- land birds this time. This photo and the next were not taken at Mai Po itself, but I certainly saw enough of the birds they show on my day there. This one is a Light-vented or Chinese Bulbul (Pycnonotus sinensis), one of the commonest and most obvious birds at Mai Po and indeed everywhere else in Hong Kong, even in in the midst of the city.

Not as common, but quite a bird when it does show up, is the Masked Laughingthrush (Garrulax perspicillatus). Laughingthrushes travel in noisy gangs like jays, though they are more likely to stick to the shrubbery. The Masked is far from being the most colourful of the laughingthrushes - there are some really stunning ones in China and Viet Nam, for example - but they have lots of character, and they certainly livened up my day.

The Azure-winged Magpie (Cyanopica cyana), a much more softly beautiful bird than this photo indicates, is native to China but is introduced in Hong Kong, probably as the result of captures for the bird trade. This was one of a group hanging about at the reserve entrance.

On the basis of call alone, the most abundant land bird on the Mai Po reserve may be the Yellow-bellied Prinia (Prinia flaviventris). Not only are there lots of them in the reeds, but they are remarkably persistent singers, repeating their short songs over and over again well into the heat of the day. My birding friends in Sarawak may be surprised to see how different this bird looks from the equally common and noisy, but far less yellow, Yellow-bellied Prinias on Borneo.

During migration, a number of rather plain warbler species may pass through Mai Po. This Dusky Warbler (Phylloscopus fuscatus), however, is probably a wintering bird. Unlike most leaf warblers, it tends to stay fairly close to the ground; this bird, working its way through the scrub separating two of the gei wais, even foraged on the ground at times.

Eventually, after wandering among the gei wais, I came to this rather fearsome-looking fence (complete with a guard tower and rolls of barbed wire) separating the territory of Hong Kong from the rest of China. On the other side, accessible through a small gate, is the second part of the reserve: the mangrove swamps and mud flats lining the eastern shore of Deep Bay.

To reach the mud flats, I had to cross a long, narrow and rather unsteady boardwalk threading its way through the mangroves over a series of floating oil drums.

As soon as I passed through the border gate I found myself looking down at numbers of fiddler crabs scuttling over the mud flats or waving their enormous claws in display. There are, apparently, six species of fiddler crab at Mai Po (for details, with lots of pictures, see www.afcd.gov.hk/english/publications/publications_con/files/12.pdf). This one appears to be Uca arcuata.

Fiddlers were not the only crabs under the boardwalk or out on the mud flats. This is Parasesarma plicata, a common mangrove crab of the family Grapsidae and a feeder on bits of leaf litter and other detritus in the mud.

Eventually I came to the end of the boardwalk, and a hide (or, rather, two of them, on different spurs of the trail) looking out across Deep Bay itself towards the city of Shenzhen in Guangdong Province, China. The hide is supposed to allow you close views of the huge numbers of shorebirds, gulls and other things that throng Deep Bay in winter. Of course, to enjoy close views the birds have to be close, and they decidedly weren't. I could see clouds of them in the distance, but except for a few egrets there was practically nothing within identifiable reach.
This immature or winter-plumage Chinese Pond-Heron (Ardeola bacchus) came closest -- but it was still a fair ways off...

That doesn't mean there was nothing to see. I had an entertaining hour being amused by the antics of mudskippers, semiterrestrial froglike fishes that spend their days hopping about out of water (but which are otherwise typical gobies, having nothing to do wit those other fishes, our ancestors, that crawled out onto the land in the Devonian). There are three species at Mai Po.
This is the largest, Boleophthalmus pectinirostris. Males have huge sail-like dorsal fins that they show off in display, but I only saw a little of this. To get a better idea of how spectacular this fish can be (and for lots of information about mudskippers in general) see themudskipper.org.
This is the smallest, Periophthalmus modestus (formerly known as P. cantonensis), the Chinese Mudskipper. There is a third species, Scartelaos histophorus, but I am not sure that I saw it; there were a lot of quite small and slender mudskippers about that could have been the young of any of the three.

The two species I saw look, and act, very much alike at first blush, but apparently they have some pretty striking differences. According to a thesis by Phoebe Chan Ka Yi at Hong Kong University, for example, while P. modestus is a carnivore catching and eating a wide range of small invertebrates, B. pectinirostris is a specialized vegetarian that eats practically nothing but algae and diatoms.
I had to leave before the tide came in, so I never saw the birds swarm up to the hide - but occasionally a few Great Cormorants (Phalacrocorax carbo) flew over on their way inland, a taste of what I might have seen had the tide come in. I'll just have to go back one day -- and I hope, one day, that I will.

2 comments:

  1. Ronald, delightful post. http://www.ccs-hk.org/DM/butterfly/Geometrid/Dysphania-militaris.html will give you the larval view of D. militaris. False Tiger due to it belonging to Family Geometridae, as opposed to the Tiger Moth Family, Arctiidae. Suspect you may find the later instar larvae of the False Tigers to be loopers - inchworm - move like a leech. A moth from Geometridae common to Hong Kong is Utethesia lotrix, the Crotalaria Moth. I post, when I get time, a lot of this kind of material on my Facebook ... Andre Jagger.

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  2. Thanks! I'm not on Facebook myself - but am currently working on a book on butterflies and (to some extent) moths for Firefly Books, so I appreciate the reference.

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