wgeoff

At about 5.10pm on Tuesday evening, a Booby flew past my seawatching station on Po Toi heading NE. I assumed it was a Brown Booby until I looked at the photos later that evening, here are 6 photos plus 3 enlargements



As it was very misty and the light was bad, colours have not come out well on the photos and they are mostly black, grey and white. Nevertheless, I think it is possible to identify the species.

A Booby in this region with dark upper wings and head and white underparts should be either a Brown Booby or an immature Masked Booby. I think this is an immature Masked Booby for the following reasons

1. It has a complete white collar going right around the back of the neck
2. The breast is white up to the throat
3. The underwing is extensively white with a thin dark central line
4. The back and forewing is a lighter brown colour
5. The head and scapulars have white patches indicating moulting into a white colour

These features should not appear in a Brown Booby but are expected in an immature Masked Booby, according to Robson 'Birds of SE Asia' and National Geographic 'Field Guide to the Birds of North America'. I think the complete white collar as seen in all the photos is a critical feature.

Comments please.

[ Last edited by wgeoff at 18/08/2010 17:49 ]

kmatthew

I agree this is a Masked Juv.

http://www.ecuador-travel.net/galsite-princesteps1.jpg

The photo above shows the white neck, similar to Geoff's bird.

Which ever booby it is, a great find!!

yyattung

Congratulations! I am convinced!

The nearest breeding site of Masked Booby is around Diaoyu Island.

So, it shows there is a chance for the albatrosses to come to HK!!

kmike

Another first for Geoff and Po Toi - congratulations!!

Anyone predict this to win Graham's bubbles?

Mike K

wgeoff

Thanks everyone for their comments.

This sort of bird makes up for the hours spent watching an empty sea.

cmichaell

Geoff,

Congratulations again on another first for Po Toi and Hong Kong, and another quality seabird.

Many boobies and gannets often have confusing immature plumages. and care is needed. However, in this case, fully agree with your ID that its an immature Masked Booby for the reasons you have given. The clear cut relatively broad white collar seperates from all other dark-headed immature boobies [ie Brown, Red-footed, Blue-footed and even Nazca, recently split from Masked in the Galapagos, which can occasionally show a white collar but not as broad or clear cut].

Seperation from Brown is also confirmed by the white upper breast whereas Brown has the dark from the head extending down to the lower breast. The white underwing with narrow dark line extending from carpal to near the axillaries is also just right for Masked, and the white on the scapulars indicates changing to white adult back plumage, not brown.

Red-footed generally has a paler head than back, and darker underparts, without the clear cut back demarcation between dark head and breast. Also the underwing is usually darker and messier.

Blue-footed has a white nape patch but this is not connected to the white breast to form a collar. Blue-footed also has white upper tail coverts, whereas your bird appears all dark above.

On range, Masked is known to breed in the Senkaku/Diaoyutai Islands [with Brown] and is regular in the East China Sea whereas Blue-footed and Nazca are only known from the opposite side of the Pacific. Note Red-footed used to breed closer at the Paracels in the South China Sea but is ruled out above.

Lastly, your bird appears to be in wing moult [inner primaries] and back which fits post juvenile moult of last summer's fledglings. This would make its age first winter heading for first summer. Masked Boobies take 3 years to gain adult plumage.