2010 Mass flowering of dipterocarps in Sabah

General flowering is a community-wide masting phenomenon (Masting is the intermittent production of large seed crops by a plant species synchronized within a population (Kelly, 1994), which is thus far documented only in aseasonal tropical forests in Asia. Although the canopy and emergent layers of forests in this region are dominated by species of a single family, Dipterocarpaceae, general flowering involves various plant groups. Studying proximate factors and estimating the flowering patterns of the past and future may aid our understanding of the ecological significance and evolutionary factors behind this phenomenon. 

Here we show that this phenomenon is most likely triggered by irregular droughts based on 10 years of observations. In the aseasonal forests of SE Asia, droughts tend to occur during transition periods from La Niña to El Niño, which results in an irregular 6–7-yr cycle involving a dry period with several droughts and a wet period without droughts. 

The magnitude of a flowering event also depends on the timing of droughts associated with the El Niño southern oscillation (ENSO) cycle, with the largest events occurring after an interval of several years with no flowering. Because most plant species can only reproduce successfully during large flowering events, changes in the ENSO cycle resulting from global warming, may have serious ramifications for forest regeneration in this region.  

(Shoko Sakai et al, 2006, American Journal of Botany. 2006;93:1134-1139.)

We witnessed the mass flowering in our forest in early April 2010, after the onset of rain after a prolonged drought of 2 to 3 months. Here are some photos of this phenomenon.

Scarlet-backed Flowerpecker and Juvenile

Scarlet-backed Flowerpecker Dicaeum cryentatum is the second commonest flowerpecker (after Orange-bellied Flowerpecker D. trigonostigma) in Borneo. The male shows unmistakable scarlet crown, back and rump. The female shows red rump. Nevertheless, a variety of color morph has been reported, including a singing male with black back in Tawau (Gretton 1990), a specimen from Banjarmasin, Kalimantan Selatan, has red crown and back, but is otherwise female in plumage. Hybridisation with Scarlet-headed Flowerpecker D. trochileum (which does not occur in Sabah) has been recorded near Samarinda, Kalimantan Timur.

Undoubtedly the field identification of juvenile birds can be nightmarish at times, unless you witness the adult birds together as well.

Description of the juvenile of the Scarlet-backed Flowerpecker by Robson's Field Guide to the Birds of Southeast Asia (2008) is that it is similar to female, but basal half of bill mostly reddish pink, underparts uniform with orange-tinged upper tail-converts, throat and breast more uniform greyish. Susan Myer (2009) says it is like female but lacks red on rump, underparts buffier, no mention of bill color though.

Here are pictures of the female and juvenile, the bill color of the juvenile is more yellow-orange rather than as described by Robson.

Female bird, note the red rump.

Juvenile bird.

Nearer bird is juvenile, further bird is adult female.

Happy Birding.

Photodocument of Wild Birds of Borneo 

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Grey-bellied Bulbul

Grey-bellied Bulbul Pycnonotus cyaninventris is a very scarce resident of the lowland primary and secondary forests, swamp, ladang, cocoa and rubber plantation, forest edge and often along rivers. Near threatened (BirdLife International 2001).

Their food consists of green berries and Trema orientalis berries, and insects, usually seen in mixed flocks at fruiting trees with barbets, bulbuls, leafbirds and pigeons . Denis M. Batchelor saw them hawking rising ants or termites. (Rising ants or termites is quite a common event in the early morning after a night  or few nights of rain, winged reproductive forms of ants or termites are seen flying out from the nest hole in the ground in large swarms, such swarming behavior is usually synchronized by other nearby colonies so large numbers of winged ants suddenly appear, attracting numerous feeding birds catching them on the wings. I witnessed Asian Glossy Starling Aplonis panayensis, White Breasted Woodswallow Artamus leucorynchus, Eurasian Tree Sparrow Passer montanus, Java Sparrow Padda oryzivora and Chestnut Munia Lonchura atricapilla feeding on them  as they flew out form their nest hole in front on my home. No doubt the composition of the predating birds would be different in the forest setting.)

Two birds were photographed  in Tawau, saw them flew in to feed on tiny black ants on the tree trunks, the ants are visible in the second photograph.

 

Grey-bellied Bulbul

This is my new bird and bring my count of photographed wild birds of Borneo to 311.

Happy birding.

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Finsch's Bulbul

Borneo has 25 species of Bulbul, including 2 endemics. Out of the 25 species, 17 species are from the genus Pycnonotus, and 4 species from the genus Criniger.

Finsch's Bulbul Criniger finschii, is a scarce to local common sparsely distributed resident of the lowlands and secondary forests.

This genus of Bulbul differs from the Pycnonotus genus in that it shows a patch of long feather at the throat, giving a bearded appearence.

This is photographed in Tawau and my number 310 photographed wild birds of Borneo.

Happy birding.

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Notes on Taxonomy

Bulbuls are tropical forest birds distributed in Africa and Asia. Among some 15 genera, only two, Pycnonotus and Criniger, are common to both continents. All African Pycnonotus seem clearly related to the Arabian species and to some other Asiatic species.Conversely, the five African and six Asiatic bearded bulbuls of the genus Criniger  are also thought to be related. 

In the broad sense, the generic name Criniger is better characterised by its conspicuous throat patch with long feathers and by their numerous and long hair-like feathers on the nape, than by the general shape of the bill – strong, high and hooked – or the plumage – very long and soft.

However, evidence from two mitochondrial genes suggests that the Asian members of Criniger form a clade distinct from the African members, and should be separated as the genus Alophoixus Oates1889 (Pasquet et al 2001). Although the distinct finschii did not form part of their study, they tentatively placed it in Alophoixus. Dickinson & Dekker (2002) did not accept this generic split as Alophoixus was erected for phaeocephalus (Yellow-bellied Bulbul), based on the distinctiveness of this form, to separate it from other Asiatic member of Criniger, and because Alophoixus may itself require splitting. Fishpool & Tobias (2005) use the genus Alophoixus, but suggest that this species may be better placed in a monotypic genus.

IOC in its update in IOC Version 2.0 (January 2009) has put all the Asian Criniger bulbul under the genus Alophoixus based on Fishpool & Tobias (2005).

Both Craig Robson's A Field Guide to the Birds of South East Asia (2008) and Susan Myers's A Field Guide to The Birds of Borneo (2009) follow the IOC list.

Clive F. Mann's The Birds of Borneo An Annotated Checklist (2008) and Quentin Phillipps's Field Guide to The Birds of Borneo (2009) use the genus Criniger.

Oriental Pratincole

Oriental Pratincole Glareola maldivarum, is a winter visitor form the North, a passage visitor and also migrant breeder. They are gregarious birds, often forming large flocks, largely crepuscular (active at twilight), feeds by running and lunging after insects on ground.

In April 1981, large number were found in Tampasuk plain, several nests were found near birds that were hesitant to fly, each nest usually containing one brown-blotched egg and a downny young which tried to scurry off.  However, in 1982, only few birds were present and no nest was found.

Thousands of Pratincoles were observed on Tampasuk plain on 9th March 1983 (Western Foundation of Vetebrate Zoology)

In 1987 and 1988 they were reported to try to breed and raise young in Brunei. There were at least 62 at Kota Belud in Jun 1998 but no nest was found. Smythies concluded that there might be a spread of breeding population that appeared to migrate away from breeding site or out of Borneo.

This single bird in breeding plumage was photographed in Tawau in February, first record from the East Coast of Sabah, perched on a freshly plowed field used for open pit sand mining. My number 309 wild bird of Borneo.

Oriental Pratincole

Happy birding.

Photodocument of Wild Birds of Borneo #309

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