Thursday, 24 December 2020

Christmas Rarity - Eurasian Oystercatcher

This year had been exceptional for rarities, and one of the most long awaited rarity that turned up is an Eurasian Oystercatcher, this is only the 3rd record in Hong Kong that I am aware of, of which I missed both previous times. This bird was actively feeding along the mudflat looking for razor clams. Despite being quite common in Europe, Eurasian Oystercatcher is not that common along the coast of Southern China, naturally limiting to the coast of Fujian, they very rarely venture as far south as South East Asia. All previous records in Hong Kong had been from Deep Bay area, and this one was no exception.

Eurasian Oystercatcher

Nobody really knows why this species is not recorded in Hong Kong more often, as they are unlikely to be overlooked, their large size and conspicuous plumage means they don't really blend in well with other waders. Either way, this was a very special bird that is certainly one of my favourite Hong Kong ticks this year.

Eurasian Oystercatcher - inflight

Around the same area Western Ospreys can often be seen, patrolling the coast for fish, occasionally flying quite close to the shore. Despite being quite common, they are by no means boring birds to look at.

Western Osprey

I haven't been birding that much of late, but other notable bird sightings were a male Siberian Rubythroat near Tai Lam Ecological Garden, like any other Rubythroats I have seen it was quite shy, but showed long enough for a record photo. At Lam Tsuen I was greeted by a flock of Asian House Martins, I haven't seen much of them this year, so I am glad to get them on my year list.

Siberian Rubythroat - male

Asian House Martin

Hoiling and I finally got around to visit a wintering butterfly roost at Tai Lam, and it was quite the spectacle, with over thousands of butterflies clinging onto trees and flying around. The exact reason for this spectacular congregation is still not known, but it is likely that by staying together they are safe from predation (although many butterfly species of Danainae are poisonous anyway). It is also incredible to think that these butterflies goes through 4 - 5 generations per year, how they find their way back to the exact location each year is mystifying to me.

Wintering butterfly roost

Most of the wintering species are Blue Spotted Crow (Euploea midamus) and Common Indian Crow (Euploea core), but there were other butterfly species present at the site, including numerous Grey Pansy (Junonia atlites) and Mottled Emigrant (Catopsilia pyranthe). 

Grey Pansy - Junonia atlites

Mottled Emigrant - Catopsilia pyranthe

Other Danainae species includes Plain Tiger (Danaus chrysippus), Glassy Tiger (Parantica aglea) and Blue Tiger (Tirumala limniance), none of these species rare, but seeing them in good numbers was still pleasing.

Glassy Tiger - Parantica aglea

Blue Tiger - Tirumala limniance

Plain Tiger - danaus chrysippus

The species that out numbered everything else was no doubt Blue Spotted Crow (Euploea midamus), although a common species in Hong Kong, you are unlikely to see so many in one place as you will at a wintering roost, they are not bad looking butterflies either, although they may look dark brown from afar, in the right lighting they are iridescent blue!

Blue Spotted Crow - Euploea midamus

Nature never seize to amaze us, and mimicry in nature is always something that fascinated me. How can one species evolve to look so much like another? Here is a butterfly that at first glance you may think look very much like another Blue Spotted Crow, when in fact it is a Great Egg Fly (Hypolimnas bolina), which actually belongs to a whole different family altogether!

Great Egg Fly - Hypolimnas bolina

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