Messages from the Cinereous and Streaked Bulbuls

The Cinereous Bulbul Hemixos cinereus and Streaked Bulbul Ixos malaccensis are both uncommon to rare species in Singapore. However, once in a while, they appear in numbers all across Singapore. What can we infer from these sightings?

In the winter of 2014/2015, Singapore experienced a flood of Cinereous Bulbuls and Streaked Bulbuls. An influx of some sort, it seemed. These typically uncommon bulbuls appeared all over the country, with observations including a flock of nearly 200 Cinereous Bulbuls at Pulau Ubin. During that period, many other surprises showed up: two separate Green Broadbills, Yellow-eared Spiderhunter, Yellow-vented Flowerpecker, and Thick-billed Flowerpecker to name a few. Most of them were species that are rare visitors to Singapore (the Green Broadbill especially, being the first two records since their extirpation in 1941) though common in the lowlands of the region, such as the forest patches of Johor just an hour’s drive by car, or the islands in Riau a boat ride away. The next few seasons were lacklustre with regards to these groups of birds despite the rapid spike of birdwatchers in the country. Both bulbuls only appeared sporadically and in much smaller numbers, and regional lowland rarities (?) continued to be found but at a rather slow pace. In the 2018/2019 season, a handful of Cinereous Bulbuls appeared and were once again accompanied by some Streaked Bulbuls. Their numbers dwindled through summer, and the 2019/2020 season was a similar case. Then in the winter of 2021/2022, Singapore observed a familiar scene of mass Cinereous Bulbul arrivals. Streaked Bulbuls followed suit, and multiple rare regional species showed up in Singapore as if their calendars were synchronised: two Black-thighed Falconets (the first since 1990), Green Broadbill (first since 2014), Scarlet Minivet (first since 2001), Yellow-vented Flowerpecker, and Scarlet-breasted Flowerpecker (first confirmed record for Singapore). The peaks and troughs of Cinereous Bulbul (blue), Streaked Bulbul (red), and locally significant Sundaic visitors (green) sightings in Singapore. Sundaic visitors are considered “locally significant” for the purposes of this illustration if they have less than 10 records in the last 10 years. The table below this article lists all the records of these locally significant Sundaic species from this illustration. Note that a single record is defined as an individual or group of individuals present at one site for a period of time. So although there were hundreds of Cinereous Bulbuls across Singapore in both the 2014 and 2021 peaks, the number of records is far smaller. These sightings are more than just déjà vu; they possibly hint towards some form of ecological force driving the birds southwards that we are yet to understand (assuming they primarily came from Johor). Indeed, unorthodox movements of birds – be it at a large or small scale – are periodically observed. In 2019/2020 we had a spate of Indochinese birds arriving in Singapore, and just last season we were kept busy with species that typically winter in the Indian and Middle-eastern region (remember the Cinereous Vulture, Amur Falcon, Black Redstart and Spotted Flycatcher?). Very recently in May we also observed a rush of regional species to Pulau Ubin, with Black-and-red Broadbill, Black-and-white Bulbul, Lesser Green Leafbird and Scarlet-breasted Flowerpecker showing up. Strangely, Cinereous and Streaked Bulbuls were absent from the rave, and the birds were concentrated to Chek Jawa but not elsewhere in Singapore – perhaps the cause for the latest event differs from the seemingly periodic influxes we get. Could it have been due to land-use change in the region? Was there a particular tree in Chek Jawa blocked from our views that provided a very attractive food source? We don’t know, and these are at best educated guesses. However, with proper housekeeping of local bird records, we might eventually be able to search for the answers to these questions. For example, reliable long-term data coupled with environmental modelling showed that the Indian Ocean Dipole event (a phenomena where the Indian Ocean’s western section becomes unusually warmer than the eastern section) led to an influx of Red-necked Phalaropes to the region around Kenya in 2019/2020). Our continued and collective efforts to document Singapore’s birds will surely play a key role in advancing our knowledge in the years to come. As for now, while our understanding is limited, the patterns suggest one thing: get your gears prepared and be on high alert when Cinereous and Streaked Bulbuls start showing up. These two species seem to serve as messengers for the rendezvous of regional birds rare in Singapore. There are many species on our checklist to look out for: Silver-rumped Spinetail, Whiskered Treeswift, White-bellied Woodpecker, Great Slaty Woodpecker, Malayan Black Magpie. Or perhaps other megas not even on the Singapore checklist – I’d like to place an order for a Brown-backed Flowerpecker please! We recently contributed an article to BirdingASIA to highlight these avifaunal records from our community during the 2020-2021 season and the possible implications behind them. As the national...