Seabird Survey in Jakarta Bay

On 16 and 17 December I was a guest of the team from Burung Laut Indonesia (Indonesian Sea Birds) for a 2-day survey in Jakarta Bay, southern Java Sea. The team has been undertaking monthly surveys since July 2011, primarily to monitor frigatebird numbers and habitat use, particularly the critically endangered Christmas Island Frigatebird (Burung Cikalang Christmas). Of course other seabirds, mostly terns and cormorants are also counted. A regular feature of the surveys is also the large number of waterbirds (egrets etc.) encountered commuting around the bay to and from the rookeries on Pulau Rambut.

We departed from Tanjung Pasir, north of Jakarta Airport aboard a small wooden boat (8 m long with a beam of 2 m, and 30 cm of freeboard) with a diesel inboard and a top speed of about 4 knots. We set a course of systematic transects through a gird of 1 km squares, visiting bamboo fish traps where seabirds routinely roost. Late in the day we circled Pulau Rambut to count the soaring flocks of frigates gathering to roost there after dark. We stayed overnight on Pulau Untung Jawa. The next day we continued transect surveys before pending storms at midday forced our little boat to shelter at Pulau Lancang for several hours.

Christmas Island Frigatebird (c. 65)*
Lesser Frigatebird (c. 10)
(Great Frigatebird?) 1
Little Black Cormorant (‘000s)
Oriental Darter (‘00s)
Great Crested Tern (c. 60)
Lesser Crested Tern (> 600)
Common Tern (81)
Black-naped Tern (c. 50)
Roseate Tern (1 adult in breeding plumage)

*A high count of 73 frigates soaring over Pulau Rambut in the evening, was mostly Christmas Island Frigatebirds. Several male Lessers were present and right on dark there was a male frigate that appeared all dark (Great?), although perhaps the poor light obscured white axillary spurs. Two different female Lessers were also seen at sea.

Other waterbirds
Grey Heron (‘00s)
Purple Heron (‘0s)
Great Egret (‘0s)
Intermediate Egret (‘0s)
Little Egret (‘00s)
Cattle Egret (‘00s)
Black-crowned Night Heron (‘000s)
Striated Heron (3)
Glossy Ibis (1)
White-bellied Sea-Eagle (8)
Osprey (2-3)
Pacific Golden Plover (15)
Whimbrel (13)
Common Sandpiper (8)

There were also about 20 landbird species on the islands.

Many thanks for a great trip to team Burung Laut Indonesia:  Fransisca Noni, Iwan Londo, Khaleb Yordan, Putri Wardhani and (the absent) Nanang Khairul Hadi. It will be very interesting to see the results of their frigatebird surveys at the end of the initial 12 months survey period.

Author: David James

Picture and cover : Khaleb Yordan

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