A recent publication in the Journal of Ornithology has some interesting new data on the breeding seasons of Singapore’s birds, and if you are an avid contributor to eBird, your observations might be a part of it.
Singapore has an incredibly dedicated birding community, and many birders share their observations of nests, baby birds, and fledglings. All those observations were taken together with half a decade of mist-netting data collected by the Avian Evolution Lab at NUS and the National Parks Board to outline the breeding season in Singapore.
If you look hard enough you can find birds building nests in Singapore just about any month of the year, but you’re much more likely to succeed if you go looking in March – that’s when most insectivores like Malaysian Pied Fantails and frugivores like Coppersmith Barbets and Black-naped Orioles are constructing nests. Granivores like Baya Weavers nest a bit later in the year, the best chance to catch them constructing their charismatic hanging nests is in June. You’re most likely to come across active nests with unhatched eggs if you go looking in April or May. June to July is the best time to see parents feeding their fledglings, and very young birds still chasing their parents begging for food. By the time August comes around the breeding season is over, but if your field ID is particularly good you might be able to recognise juvenile birds still in their first set of flight feathers.
It’s always exciting to see nests and baby birds but remember not to get too close. Its stressful enough being a parent.
Another example of a very widespread frugivorous species, the Black-naped Oriole. They are very common in Singapore, but finding their nest takes a bit of effort! Photo credit: Goh Cheng Teng
Granivorous species like the Baya Weaver , known for their intricate nests, tend to breed later in the year. Photo credit: Keita Sin, taken in Malaysia
Insectivorous birds like the Malaysian Pied Fantail that likes to nest near waterbodies often nest around March. Photo credit: Keita Sin
Frugivorous birds like the Coppersmith Barbet tend to nest around March too. Photo credit: Goh Cheng Teng
And so it’s been a year since we launched the Singapore Bird Database. Time really flies. This time a year ago, the Fairy Pitta at Hindhede Nature Park that we queued for was already gone, and many of us were busy chasing Singapore’s first proper documentation of the Grey-streaked Flycatcher.
Nostalgia feels good, but for now, let me share some updates on our database.
Our database was launched to provide a platform where anybody can easily find relevant information regarding rare bird species in Singapore. Since then, we’ve received over 25,000 views on our database website, and we’re glad that many of you have found our work useful. For those who are keen to find out how our platform came to life, you can check out our blog post or detailed write-up.
Information available in our database has almost doubled over the past year, and it now contains over 2000 records from more than 180 species. While many were compiled from social media archives, publications, and past eBird records, nearly 300 were submitted by none other than all of you – birders in the field – to which we would like to express our huge thanks to. 300 submissions, only for rare birds! All of these submitted records were evaluated by our Singapore Bird Records Committee team, whose latest works are constantly updated in our Recent RC Decisions page. We’ve been very busy – a happy problem because it means that our community has been finding a lot of good birds!
Moving on to how the Singapore Bird Records Committee has evolved since then, first, we have developed an operational guideline that can be viewed in a Q&A format here. Second, we are renaming the term “Rarity” to “Review Species” in our checklist. It might sound like a matter of semantics, so allow us to explain. Our Records Committee makes a concerted effort to properly evaluate and document records of birds that one might not necessarily think is that rare. Say, Pied Harrier. This is an annually recorded raptor, but in numbers small enough that warrants celebration. This season, we seem to be witnessing a strange spike in their numbers for reasons unknown, and patterns like this will be missed if not for proper efforts. Another good example is the form of Barn Swallows with rufous underparts. we occasionally observe At present, we don’t even know which subspecies actually arrive here, but what we do know is that they are rare in Singapore, and that records keeping would be essential for future generations to have a point of reference when the ornithological community one day have a better understanding of these birds. In principle our workflow stays the same, and so we’d greatly appreciate it if you could submit your encounters. This terminology change will be reflected in our Species Pages as well in due time.
Our database has changed in more ways than one, and here is a comparison of how it looked 1 year ago versus today. Besides new features and useful tools, the layout now emphasises images and is more colourful and easy to use. An archived version of our website from Nov 2021 is available here.
Last, our database works have extended beyond collating records, and we’ve designed useful tools for everybody’s birding activity. Our Monthly Roundups provide accurate information on interesting species documented each month, and our bar charts can help you plan your birding itinerary to best target the species that you really want to see. If you’re hungry to find the next Mega in Singapore, you can also refer to our On This Day page to find gems from the past.
Moving forward, we aim to revisit all of our Species Pages for further improvements, and also plan to expand our database and website to include more species. If you have ideas for collaboration or are keen to help out with our work, don’t feel shy to get in touch with us!
I’d wrap up this update with the most important bit, the acknowledgements.
See all those Monthly Roundups and Bar Charts? They didn’t just fall out of the sky (though the birds did) – they were possible thanks to the tech-wizardry of Raghav, to whom we extend our utmost gratitude.
See those crazy numbers of historical records newly compiled in our database? They were collated and scrutinised by our amazing Singapore Bird Project teammates Clarice, Geraldine, Jenwei, Jing Ying, Hong Yao, Hui Zhen, Raghav, and Zachary. Massive, massive thank you for the hard work – checking through all those records is really not easy.
And lastly, to all the birders for your all-rounded support and for sharing and submitting your sightings – the Singapore Bird Records Committee thanks all of you.
See you all in the field and happy birding!
PS, IN CASE YOU MISSED IT:
We were invited by the Lee Kong Chian Natural History Museum to give a talk about our database in March 2022. Check it out too if you couldn’t join us!
In a recent post, we covered the why of our migrant bar charts – what motivated us to design a new way to present migration data? In this post, we will try to explain how our methodology works, and look at some examples of the algorithm in action.
Recently, a large volume of work in the field of ecology has been concentrated on generating robust avian population estimates, with a variety of different methods. One feature common to a number of the techniques has been a focus on applying citizen science data, especially from the eBird platform, as in Hansen et al. (2022).
Over the last few months we have designed a straightforward technique to model migration patterns and trends in Singapore. Rather than making population-wide range and abundance estimates which require more sophisticated methods, like in eBird Status and Trends (Fink et al., 2021), we instead focus only on analyzing occurrences within Singapore, which are fine-grained and relatively well-represented in citizen science datasets such as eBird.
The effect of confounding variables such as uneven effort distribution is relatively low due to Singapore’s small size and high observation density, so our approach only incorporates recorded observations and makes no attempts to estimate unknown quantities using extrapolation.
We consolidate observation data using spatial and time-based constraints. Important terminology that we use to describe the process are defined:
Sighting: one eBird observation of a species, extracted from the eBird dataset; the important information which is used is: species name, number of individuals, date, and location.
Record: one or more eBird observations of a species where the observations in question all relate to the same individual(s) – one record may comprise sightings of different numbers of individuals
Individual: a single bird of one species, may be seen multiple times or just once, and alone or together with other individuals
What this all means is that we need a method to map sightings to individuals. For instance, consider the following sightings of Yellow-rumped Flycatchers in late Sep 2021.
Tuas Bay Street
Jurong Lake Gardens (inc. Chinese Garden and Japanese Garden)
Jurong Lake Gardens (inc. Chinese Garden and Japanese Garden)
Changi Business Park
Singapore Botanic Gardens
Dairy Farm Nature Park
Tuas South (Tuas South Avenue 16 and surrounds)
Jurong Lake Gardens (inc. Chinese Garden and Japanese Garden)
Singapore Botanic Gardens
Tuas South (Tuas South Avenue 16 and surrounds)
Simply choosing the high count of 4 is not a good idea, since there are clearly more than 4 unique birds in the table here. At the same time, adding them up won’t work because the 26 Sep sighting and the 30 Sep sighting at Tuas could possibly involve the same birds.
So our approach is summarized as follows:
For each species, we deliberate and determine a reasonable “date threshold” which determines the maximum date difference between two sightings for them to be grouped together as one record. For raptors, the threshold is normally a shorter period because most sightings are of birds just passing through. Winter visitors will have longer thresholds.
For any species, our algorithm will “lump” sightings across multiple dates into a single record if the gap between them is less than or equal to the decided threshold and the sightings are less than 2km apart.
We repeat this process for every sighting until they are all categorized. Each record will have one or more sightings.
To estimate the number of individuals observed during the timeframe, we take the highest count of individuals sighted in each record and add them all together.
The below example is a color-coded example showing how each sighting is grouped according to location and date. The total number of individuals outputted by the algorithm, for the period 25 Sep to 30 Sep, would be 12, which is the sum of 1, 2, 3, 2, and 4 (highest count for each respective record, listed in bold in the table below).
Tuas Bay Street
Jurong Lake Gardens (inc. Chinese Garden and Japanese Garden)
Jurong Lake Gardens (inc. Chinese Garden and Japanese Garden)
Jurong Lake Gardens (inc. Chinese Garden and Japanese Garden)
Changi Business Park
Singapore Botanic Gardens
Singapore Botanic Gardens
Dairy Farm Nature Park
Tuas South (Tuas South Avenue 16 and surrounds)
Tuas South (Tuas South Avenue 16 and surrounds)
After dividing the year into week-long chunks and taking the average over ten years, the result is quite smooth and matches our prior understanding quite well. In the case of Yellow-rumped Flycatcher, we can see the two clear peaks in fall and spring.
How our approach compares with other publicly-available statistics
The other main source of bar charts is on eBird. Because eBird is built for users around the world, it cannot take advantage of the unique features of data in Singapore: namely the high density of observations here compared to other places. We wrote about how our method differs from statistics available on eBird in our earlier post, which has a full explanation.
This method of course only yields estimates, as some – not many – sightings which are from the same location are listed at different eBird hotspots which are more than 2km apart. Also, sometimes birds may hang around longer or shorter than the threshold decided for the species. The other problems that come from working with citizen science data are also reflected, like in the case of misidentification, incorrect location data, incorrect date information, and so on. Generally, the impact of these issues is not large and tends to cancel out, but are still problems to be aware of.
The data is also not intended to be a population estimate but rather an estimate of the observed number of individuals. The difference is that we do not infer records where data is not available, which would allow for a complete population estimate.
The algorithm is also optimized for Singapore’s uniquely high number of active observers, coupled with the tightly-packed hotspots here. In larger countries, the distance between observations would make it difficult to apply our approach.
Further possible improvements and applications of the model
In future, we hope to further improve the model by considering low counts which may be the result of undersampling rather than actual low abundance. Particularly for pelagic species, higher perceived abundance may be due to a lower number of pelagic trips during certain times of the year.
We may also attempt to extend the model to display spatial abundance in addition to temporal abundance, to highlight the best areas for different species.
We wrote this post to highlight the key features of the algorithm which serves as the foundation for our newly-released migrant bar charts. Besides these charts, it also forms a basis for our internal analyses and discussions, which eventually lead to work such as our Records Committee’s rarities list.
We’ll continue to document any further updates to our methodology in a timely manner, and as always, constructive criticism is very valuable and will help us improve going forward. Please feel free to contact us!
Hansen, B. D., Rogers, D. I., Watkins, D., Weller, D. R., Clemens, R. S., Newman, M., Woehler, E. J., Mundkur, T., & Fuller, R. A. (2022). Generating population estimates for migratory shorebird species in the world’s largest flyway. Ibis, 164(3), 735–749. https://doi.org/10.1111/ibi.13042
Fink, D., T. Auer, A. Johnston, M. Strimas-Mackey, O. Robinson, S. Ligocki, W. Hochachka, L. Jaromczyk, C. Wood, I. Davies, M. Iliff, L. Seitz. 2021. eBird Status and Trends, Data Version: 2020; Released: 2021. Cornell Lab of Ornithology, Ithaca, New York. https://doi.org/10.2173/ebirdst.2020
I’m sure many of us have used eBird bar charts in the past, and they’ve certainly helped me in deciding where to go birding or what to look for. So why did we make our own migrant bar charts here at SBP?
In this article, we’ll explore some of the drawbacks we noticed with eBird bar charts, and how our migrant bar charts stack up against eBird’s. We’ve also got a future article lined up in which we go more in-depth into the inner workings of the algorithm, so do stay tuned if you’re into that sort of thing! (Update: this post is now posted on our blog)
Because eBird is built for users around the world, it cannot take advantage of the unique features of data in Singapore: namely the high density of observations here compared to other places.
eBird mainly uses two alternative methods to try to quantify abundance/frequency for its bar charts.
This method uses the percent of checklists in which a species appears. This does not really tell us anything, because birders go to different places during different times of the year. Let’s say a certain wader is more common in November than in September. But because many people are at Henderson Waves instead of Sungei Buloh in November, the percent of checklists which contain that wader would obviously be much lower than in September. That would not reflect the species’s true status. Another problem with this method is that a checklist with 100 individuals of a certain species counts the same as a checklist with just 1 individual. And to make matters worse, an “incomplete” checklist – one where the observer says that not all birds that were seen are listed on the checklist – is not counted at all.
The difference between September and November is stark, despite just the two-month difference. It highlights the shift in observer coverage from shorebird areas in Sep (mainly Sungei Buloh) towards other habitats in Nov.
The second indicator used by eBird is the highest count of a bird for a week in history. This also poses major problems. Consider the example of the Japanese Sparrowhawk Accipiter gularis. The highest count was on 13 Oct 2020, with 104 birds, and from the eBird chart, you would imagine Japanese Sparrowhawk is most common in the first half of October. But the highest count for a certain week is not the best way to gauge abundance. To take an extreme example, if we simply take the highest count, 1000 birds split into groups of 100 each would appear like a lower level of an abundance than 104 birds seen once. And indeed, this seems to be the problem with Japanese Sparrowhawks, which are far more common in end-Oct despite the high count telling us otherwise.
From the above chart taken from our bar charts, you can see the peak for Japanese Sparrowhawk lies closer to the end of Oct, with rising numbers through October and falling numbers in November.
We’ve used eBird bar charts in the past too. We noticed these issues, and set out to design a more robust algorithm which uses all available data rather than only considering high counts or frequencies. The algorithm uses eBird’s dataset of observations too, but processes the sightings differently.
These new bar charts are the product of years of hard work from the Singapore birding community. Your observations have formed the basis for the raw data that we now have access to in eBird. Now, with your help, we have found a way of presenting information that is easily understood and has proper scientific grounding.
In the coming weeks, I’ll be writing about how our algorithm consolidates many thousands of individual eBird data points to estimate the abundance of each species over time – we’re always making an effort to ensure our approaches are firmly rooted in science, and striving to be transparent about it too. (Update: this second post is now posted on our blog as well)
Regardless of where you come from, you’re missing out on the Singaporean experience if have you never queued long long for food before. And it seems that our locally found parrots know that too! Here are some intriguing observations on the feeding behaviour of three parrot species – Tanimbar Corella, Coconut Lorikeet and Blue-crowned Hanging Parrot.
By Muhammad Nasry
Earlier this year, an alert that a stretch of mango trees around the Alexandra Village area was fruiting and attracting Coconut Lorikeet Trichoglossus haematodus began circulating online, featuring eye-level shots of this colourful parrot happily munching away at the fruit. Naturally, this attracted a whole horde of birders, myself included. Having lived near the area since birth but blithely unaware of the existence of these mango trees, I was a little embarrassed for not realising sooner, but excited by the discovery of a new birding spot just minutes from my doorstep.
And so I visited. Again. And again. And again.
Over the course of several visits I began to notice an odd pattern in terms of the foraging behaviour of some of the birds there. Consistently, this feeding pattern repeated itself over and over.
The first to arrive was usually the Tanimbar Corellas Cacatua goffiniana. These parrots seemed to prefer feeding on the outermost bits of the mango fruit, only occasionally reaching deeper into the mango for more of the pulp.
Second on the scene was typically the star attraction: the Coconut Lorikeets. They would pick up where the corellas had left off, peeling off what remained of the fruit skin. They would then proceed to rip apart the rest of the fruit (as parrots do) while eating, with the bits of fruit either being scattered on the surrounding foliage or dropping straight to the ground.
The lorikeets were often seen foraging in pairs, with the occasional dispute breaking out between pairs over mangoes. There were up to three pairs seen at the same area at any one time. In one instance, one of the pair was feeding while the other stood guard, screaming its head off to ward off any would-be usurpers of the coveted mangoes.
This feeding order was generally consistent – each parrot species usually came to feed only after the previous one had left. Competition due to size differences may explain this pecking order (pardon the pun), given that the corellas are the largest, and hanging parrots the smallest. The issue with this theory is that there were plenty of mangoes to go around, many of them a similar shade of green as the ones being eaten (which presumably indicates they were equally edible) and therefore competition was not necessary. However, the hanging parrots seemed to pass up these seemingly fine mangoes in favour of those that had already been opened by the two introduced parrot species. Perhaps letting the bigger parrots do the hard work of opening up the unripe mangoes may be more convenient for them – they may have to use a lot more effort with their comparatively smaller beaks to open up the mangoes on their own.
The messy eating habits of the parrots did not go unnoticed by other animals; there were intermittent visits to the mangoes (or to the bits of mango strewn around on the branches) by other common urban species, which included:
It is interesting that the feeding behaviour of the introduced parrot species benefited other wildlife species (birds or otherwise). It may be possible that many more species may benefit from such interactions in other habitat types as well. Ground-dwelling fruit-eaters like the Asian Emerald Dove or Lesser Mousedeer may benefit from the bits of fruit scattered around the forest floor thanks to the parrots’ poor table manners. Of course, these interactions took place in a relatively urban habitat next to a busy road – generalisations to less developed habitats would not be wise without further study.
Nasry, M. (2022) Biodiversity Record: Observations of some urban birds feeding on mango fruit. Nature in Singapore, 15, e2022095. URL
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.
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 borders start opening up, many of you who picked up this obsession hobby of birding recently must be craving to, or might have already started to explore beyond Singapore. If you’re keen to read more about birding news from the Asian region, do consider subscribing to the Oriental Bird Club! You’ll receive two copies of BirdingASIA with more exciting articles from the region, as well as one copy of the Journal of Asian Ornithology where latest research on regional avifauna are highlighted. (Just for the record, the Singapore Birds Project is not affiliated in any way to the Oriental Bird Club. We do not get any commission or benefits from promoting them.).
Happy birding, and please do share your sightings if you happen to come across any of these rarities and submit your records to the Singapore Bird Database for proper archival!
Table of records of locally significant Sundaic species, as displayed in the chart above (2014-2021)
Nussbaumer, R., Gravey, M., Nussbaumer, A., & Jackson, C. (2021). Investigating the influence of the extreme Indian Ocean Dipole on the 2020 influx of Red-necked Phalaropes Phalaropus lobatus in Kenya. Ostrich, 92(4), 307-315.
Sin, Y.C.K., Narayanswamy, R., Ng, D., Chia, S., Ng, E., & Kennewell, M. (2022). Beyond the pandemic: gems from Singapore in 2020-2021. BirdingASIA, 37, 101-108.
Streaked Bulbul at Dairy Farm Nature Park. Photo Credit: Francis Yap
Cinereous Bulbul at Kent Ridge Park. Photo Credit: Francis Yap
Juvenile Green Broadbill at East Coast Park. Photo Credit: Francis Yap
Yellow-eared Spiderhunter at Dillenia Hut. Photo Credit: Francis Yap
Thick-billed Flowerpecker at Dairy Farm Nature Park. Photo credit: Francis Yap
Yellow-vented Flowerpecker from Panti Bird Sanctuary. Photo credit: Con Foley
Black-thighed Falconet at National Equestrian Centre. Photo credit: Francis Yap
Editing by Tan Hui Zhen, infographic by Kee Jing Ying
In the winter migration season of 2021/22, our community was graced by five appearances of Himalayan VulturesGyps himalayensis. These massive birds are rare but increasingly annual migrants to Singapore and never fail to spark huge hunts for a chance to see them perched or to witness their incredible wingspan in flight.
No other species seems to unite the entire community in a truly islandwide effort as much as a flock of Himalayan Vultures slowly soaring across the island. Their size and slow flight means that regardless of where you are at the time of sighting, if they pass by your general vicinity, there is a chance you will get to see them.
Here are the accepted records of Himalayan Griffons the 2021/2022 season, as per the Singapore Birds Database:
The next day, one bird – likely one of the two seen the previous day – at Pasir Ris Park by multiple observers.
Sighting 5: 18 to 19 Jan 2022 (Bukit Batok flock)
Seven birds seen over East Coast Park by Rachit in the afternoon, last seen roosting at Bukit Batok Nature Park by Francis Yap and JJ Brinkman. All 7 birds were seen flying off the next day.
The very unique result of all the excitement surrounding Himalayan Vulture sightings is that every aspect of their presence—how many of them, their behaviour, their flight path—is quite well tracked. Combine that with Singapore’s tiny country size and the recent massive increase in community size, we have an extremely high observer density: the movement of the birds across the island were particularly well-documented on 28th Dec 2021 (Novena flock) and 18 Dec 2022 (Bukit Batok flock). The Bukit Batok flock also allowed many who could not pop their heads out of the window during work to look for them later that evening and the next morning.
Annotated flight paths of sightings 2 and 5 starting from Novena and Bukit Batok respectively, recreated based on the collective information shared by birders of Singapore through various social media groups.
All sightings from this season were of immature birds, as are most records from the region. Young birds are typically known to wander around more so than adults, and in the cases for the birds that end up in Singapore, quite far off course from where they would usually be. Records show that there’s an increasing trend in their numbers arriving over the years too. Of course, we have to be careful about extrapolating too many conclusions from this: as the number of birdwatchers go up, so do the number of rare sightings, but could other factors have contributed to their increased sightings in Singapore? Climate and land use change are speculated to have increased their occurrence in the region over the past few decades. Additionally, a vulture restaurant has been set up in Phuket since 2019. Could this have allowed some birds to accumulate enough energy to make it further south than previously possible? There have been talks on introducing such a system in Singapore too—how could this potentially help or affect the birds? There are many more questions than answers for now, much of it requiring research and discussions beyond the scope of this article.
Another slightly easier question that comes to mind is: were this season’s sightings of the same flock flying around, or new birds arriving each time? Those birds that were seen on two consecutive days at sites they were known to roost are quite surely the same individuals, but what can we make of the separate sightings? We could attempt to answer this question by examining some photographs taken across the sightings.
As seen from the images, many of the birds have rather worn wings and tail feathers, making it quite difficult to ascertain individuals. However two birds did have comparatively “unique” wear.
Interestingly, it appears that one individual from the Novena flock photographed on 28 Dec 2021 had several matching features of wear and tear of plumage. This is strongly suggestive that at least one (if not all) of the 5 Vultures from the Novena flock reappeared in the SBG flock along with the Cinereous vulture. The case is even more compelling when we note that both sightings had 5 Vultures: perhaps the same flock left Singapore on the 28th at 1300h, only to return on the evening of the 29th at SBG?
Then we notice that one bird from the Novena flock with a somewhat unique missing secondary (giving it a very “long-looking” tear) could (??) have participated in the Bukit Batok flock.. If the two photographs taken were indeed of the same bird, it suggests that the bird could have hung around the region and returned to Singapore after three full weeks! As always, it is important to keep in mind that plumage wear is common in long distance migrants and that this singular feature is suggestive but not indicative.
It goes without saying that many of the above deductions are based on guesswork, but exercises like this could bring us one step further to learning more about their behaviour in Singapore. When the vultures next arrive, taking ample photographs of them from multiple angles, will help to pin-point traits unique to individuals (if any) to help us estimate how long the birds typically stay around for.
Using plumage wear to identify individual birds is helpful in determining the number of otherwise rare migrants. The same technique was applied on an interesting case study this season elsewhere: we are quite confident that there were two Common Kestrels on the same day at Seletar Aerospace Drive. On 14 Dec 2022, one bird with strongly marked underwing coverts was photographed there by Lim Ser Chai. The next day, this species was seen again by Woo Jia Wei twice, but once at 1340h involving a bird with faintly marked underwings and broken primaries, and later at 1500h a bird that looked like the previous day’s individual!
Finally, the question that we all hope to know the answer to: what’s the best strategy to search for them again next season?
Five sightings is far from a good sample size, but the observations from this season might provide hints when searching for them again. First, if the birds are seen soaring late in the afternoon, chances are that you might be able to head down to observe them later in the evening or the next morning if they roost somewhere visible. These birds seem to have a tendency to remain in Singapore island overnight when detected later in the day. Given their massive size, they are highly reliant on thermals (rising hot air) to engage in soaring flight, making water bodies a possible deterrence for them. Perhaps this could be part of why the seven birds from the Bukit Batok flock chose to fly along the coast rather than further south to Bintan/Batam? For those aiming for flight shots, their take-off time is also likely highly dependent on the weather, though typically not too early in the morning. The Novena flock took flight around 0900h, the SBG ones around 1020h, and the Bukit Batok flock, around 1145h. Again the presence of thermals is essential for their flight, though where they might head off afterwards remains unknown to us for now.
Becoming the first person to find the vultures requires a little more serendipity. Initial sightings of Vultures are fairly unpredictable and highly dependent on being at the right time at the right place. However, knowing when to pay attention helps: previously, scarce sightings were from late December and January, but the 8 Dec 2021 proved a new early date, and no birds were detected past January despite the many occurences. For now, December to January seems to be the prime time to keep our eyes glued to the skies, and you can refer to the bar charts from our Singapore Bird Database for more information on when to look for them (and other rarities too!)
As the summer months approach, it is quite unlikely that we will see any more vultures before next season (but who knows!?). We’re approaching the season to search for possible Austral migrants and dispersals from Malaysia, but come December some of these birds might head here again. With so many pairs of keen eyes and quick cameras around nowadays, it has become easier than ever to track the habits of these vultures. The small bits of information we are able to piece together through social media may not seem like much, but as we repeat the process year after year, new insights into the birds’ habits may reveal themselves. It doesn’t take much to help: just share your sightings and submit your record to our database!
We are grateful to Con Foley, Daryl Tan, Feroz, Herman Phua, Jared Tan, Justin Jing Liang, Lim Ser Chai, Marcel Finlay, Martin Kennewell, Siew Mun, Trevor Teo, Wee Aik Kiat, Wong Weng Fai and Woo Jia Wei for sharing excellent images of the birds. We also thank the community for sharing the sightings very promptly, allowing everyone to get exciting views of the birds. Last but not least we thank the Singapore Birds Project team for comments on this article.
Praveen, J., Nameer, P.O., Karuthedathu, D., Ramaiah, C., Balakrishnan, B., Rao, K. M., Shurpali, S., Puttaswamaiah, R., & Tavcar, I. (2014). On the vagrancy of the Himalayan Vulture Gyps himalayensis to southern India. Indian BIRDS, 9(1), 19-22. pdf
Yong, D. L., & Kasorndorkbua, C. (2008). The status of the Himalayan Griffon Gyps himalayensis in South-east Asia. Forktail, 24, 57-62. pdf and associated erratum
18 May 2022: We previously mislabelled the dates for the Pasir Ris Park and Bukit Batok Himalayan Vulture photos, the map, and the first Common Kestrel photo.
Written by Yip Jen Wei with input from the Singapore Birds Records Committee
Editing by Keita Sin, Dillen Ng, Raghav Narayanswamy, Sandra Chia, & Geraldine Lee
In October 2021 a series of national firsts made landfall in Singapore in quick succession, the first of which was a male Ashy-headed Green Pigeon Treron phayrei. But unlike most of the others, there is considerably more uncertainty to the origin of this pigeon: is it an escapee or not?
To start off, there is little uncertainty regarding the identity of this pigeon. The bird is green, with a maroon mantle and wings, a yellow rump, yellow edges to dark flight feathers, chestnut undertail coverts, and a grey forehead. Going by the overall green colour and the fully developed maroon on wings, we can start from a male of the genus Treron, commonly known as green pigeons. Shown below is an image from the original sighting on 9 October 2021 as well as a list of Treron pigeons in Singapore and the field marks that rule them out:
Male has green wings and prominent orange and pink on breast
Having ruled out all known local species we can look at species beyond our shores. Visually, the only two possible matches are Ashy-headed and Grey-fronted Green Pigeon T. affinis. To rule out Grey-fronted Green Pigeon, we can look at the clear delineation of the grey crown, as well as the orange patch on the breast which is absent in T. affinis.
Now that we are certain of the identification, we are faced with the monumental task of figuring out its origin. Listed below are some of the factors that were considered when determining if this bird is a genuine vagrant or if it has origins in the pet trade:
Is this bird or related species known to migrate or travel long distances?
Is the species common in the pet trade, legally or illegally?
Is the bird in good condition?
Are there any similar cases of vagrancy?
First off, are Treron pigeons known to migrate or travel long distances? The short answer is that no, Treron pigeons do not typically undertake seasonal migration (Birdlife International, 2021), but pigeons are good dispersers and have been known to travel long distances in search of food. Similar species such as Thick-billed Green Pigeon have been recorded undergoing mass dispersal for fruit, along with small numbers of Yellow-vented Green Pigeon T. seimundi. In particular, night dispersal of Thick-billed Green Pigeons occur year-round, but peak in October-November (Wells, 1999)—incidentally this sighting of Ashy-headed Green Pigeon falls under the same timeframe. There are also hints of regular movement for Cinnamon-headed Green Pigeon to Pulau Ubin: in addition to sightings at other parts of the year, from 2018 to 2021 the species has been annual for the first week of December at the same fruiting trees in Western Ubin.
Secondly we look at the prevalence of Ashy-headed Green Pigeons or other Treron species in captivity. To answer the easiest question first: no, this species is not found in Jurong Bird Park or Mandai Wildlife Reserves. In recent published surveys from Vietnam, Thailand, Singapore, and Java, Ashy-headed Green Pigeon is also not listed as a legally or illegally traded species (Chng et al, 2015; Chng & Eaton, 2016; Eaton, Leupen, & Krishnasamy 2017; Eaton, Nguyen, et al., 2017; Phassaraudomsak & Krishnasamy, 2018). However, Treron species like Pink-necked and Thick-billed Green Pigeons have been recorded in these surveys, so it is still not beyond the realm of possibility that small numbers of Ashy-headed Green Pigeons are in the black market having avoided detection.
Thirdly, poor condition of the bird’s plumage is often cited as an indicator that the bird was once in captivity. In this bird’s case, this is not an issue: the bird is in pristine condition, from the above image there are no rings on its legs, its nails are not clipped, and its feathers are not tattered. The physical condition of the bird offers no indication that the bird was a recent escape from captivity.
It is also helpful to compare this sighting with other cases of natural vagrancy with similar characteristics: closely related species, or species with comparable ranges and movement patterns.
Here is an eBird range map for Ashy-headed Green Pigeon in the region. We can see that there are no records in Malaysia and the nearest record is in Southern Thailand, around 1200km away.
The most immediately obvious comparison is Orange-breasted Green Pigeon, another vagrant Treron with similarly only one record to Singapore from 2007 (Bird Ecology Study Group, 2008). However, this species is present in Peninsular Malaysia, with the nearest record being Port Dickson, around 250km away.
Between these two cases of Ashy-headed and Orange-breasted Green Pigeon vagrancy to Singapore, both exhibit long distance dispersal, but Ashy-headed is far more extreme. We go on to see if there are any similar cases of natural vagrancy to Singapore in the range of 1200km.
This is a range map for another species with only one record in Singapore: Hair-crested Drongo Dicrurus hottentottus. Distance-wise, its nearest records and even native range are comparable to Ashy-headed Green Pigeon. However, Hair-crested Drongo is a known long distance migrant (Birdlife International, 2021) while Treron pigeons are not. An Ashy-headed Green Pigeon’s natural dispersal is far more surprising than a Hair-crested Drongo’s migration to Singapore for the same distance. So while it is not accurate to compare one to the other, it does show that absence of a species in Peninsular Malaysia should not completely discount any case of potential vagrancy to Singapore. The fact that both these (and other) species have escaped detection on their journey south from Thailand along the Malaysian Peninsula is also not terribly unusual. Given our incredibly high observer density and position at the southernmost point of Continental Asia, Singapore has a unique advantage in detecting stray vagrants, as our stellar migration season can confirm.
Finally, here is a range map for Wedge-tailed Green Pigeon Treron sphenurus. Lone records in the centre and the western coast of the Indian Subcontinent represent extreme cases of just how wildly out of range Treron pigeons can sometimes show up at, with distances from the core range far exceeding our case of Ashy-headed Green Pigeon.
These are just some examples to show that it is not inconceivable for an Ashy-headed Green Pigeon to fly 1200km from Southern Thailand to Singapore in an interesting case of natural dispersal or vagrancy. Indeed, as with the Wedge-tailed Green Pigeon, more extreme cases of Treron dispersal have occurred.
The Singapore Birds Records Committee has placed this record in Category A (natural vagrancy) through a majority vote of 6-2. To sum things up—in making this decision, the committee considered the following:
Ashy-headed Green Pigeon is absent from local captivity and recent surveys of traded species around the region.
Treron species are capable of making such long distance flights.
Plumage and condition of the bird offer no indication the bird is an escapee.
Date and location (Central Catchment Nature Reserve) of sighting are supporting factors for the bird being a genuine vagrant.
Lack of records in Malaysia is not unusual given Singapore’s high observer density and the fact that other species have also escaped detection to Malaysia.
Of course, unless we learn to speak Pigeonese, we will never know the true origin of this bird. This offers us some interesting food for thought—what are some indicators that would reaffirm the committee’s decision or skew it toward being an escapee?
For starters, if an Ashy-headed Green Pigeon were to turn up caged or ringed somewhere in Singapore or Malaysia where it is not known to occur, that would be definitive proof that they are traded (legally or illegally) and might swing the vote against the current decision. On the other hand, if more Ashy-headed Green Pigeons or species with similar ranges and habits were to turn up nearby, it would be much harder to discount two separate sightings as repeated incidents of escapees of a bird not known to be on the market.
As with most national firsts of contentious origin, we may never have a definitive answer regarding the provenance of the bird, by nature of it being a national first record—there just isn’t enough information. At present, the best we can do is make an educated guess.
If you need help with identification, don’t hesitate to ask on our Facebook group where many regionally experienced birdwatchers are present
To find out more about our philosophy and objectives of this database, check out this write-up
Basic questions but who has the answers?
A Digital Museum. Quite a catchy name, isn’t it? Now that we have grabbed your attention, here are some simple questions that we want to ask you: How many times has the Fairy Pitta been recorded in Singapore? The answer is twice. Easy, right! It’s been all over the news recently. Okay then, what about Chinese Blue Flycatcher? Hmm, there were some recent records but it’s difficult to be certain of the total count. Two? Three? The answer is four. Well, what about the Northern Boobook? Now that’s a tough one. Does anyone have this information at their fingertips…? A rather basic piece of information, it seems—just how many times a species has been seen. Yet no one appears to have the answer.
To find out more, let’s check what Singapore Birds Project has to say about the Northern Boobook.
Local Status: Uncommon migrant
Location: Records from Tuas South, Pasir Ris Park, and Satay by the Bay but could conceivably occur in any place with trees.
This gives us some rough ideas about the species. It certainly is not a common bird, so maybe less than 20 records in total? Still we’d like to know more details. After all, it is still a highly sought after species—knowing where and when to look for it provides clues on the best way to find an individual.
Searching eBird is not particularly effective either. There are a large number of data points with some being repeats of the same sighting, and it would be too time consuming to click through every point on the map.
Finding the answer to this seemingly simple question is actually rather difficult. One would first need to make an excel spreadsheet, click through every eBird data point, then collapse possibly duplicated sightings…and that’s not all. To obtain pre-eBird era information, there would also be a need to flip through old literature to tabulate all records.
This used to be the convoluted journey that any curious birdwatcher had to take to learn about most species, but that will no longer be the case.
Introducing the Singapore Birds Database
Using our newly launched Singapore Birds Database, you can get your answer in just a few clicks. All you need to do is to search for a species name, and voila! We can see that there are at least 16 confirmed local records of the Northern Boobook. How easy is that?!
The Singapore Birds Database contains local records of over 160 species of rare birds. Not only are details on the dates, location and species name of sightings included, we also provide links to primary sources (if available online) such as Facebook or scientific publications so that anybody can verify the data for themselves. For cases where there are records of a rarity at the same (or nearby) location after a period of absence, if we think that multiple records refer to the same individual, we provide internal links so that users can cross-reference the records.
How the Singapore Birds Database was conceptualised
In 2019/2020, we had a tremendous migration season with vagrants such as a Fairy Pitta, Daurian Redstarts, and Taiga Flycatchers showing up. It was quite extraordinary and we worked to publish about its peculiarity together with Singapore’s eBird reviewer, Martin Kennewell. Researching for our paper was very challenging because basic information about a species in Singapore (e.g. how many times has it been seen) was not readily available.
We thought to ourselves, why not create a database to address this problem? In January 2020, we decided to embark on a massive projectto compile all records of significant bird species in Singapore. And let’s not just compile it for personal use. Let’s make it public. Let’s make it comprehensive. Let’s make it easy to use. Let’s make sure that it is regularly updated. Let’s make it free to use. And most importantly, let’s make it transparent. We aim for this database to provide records, substantiated with primary evidence, such that users can also question and independently arrive at answers themselves.
We reviewed over 1000 records manually by checking through every available primary source, visiting libraries countless times, and trawling through the web like crazy. After 1.5 years of effort, we are finally ready to launch this database via the Singapore Birds Project website. For those who are keen, you can find out more about the processes and philosophy of our work in this write-up.
How can you be a part of our project?
If you encounter any rare species, please submit your sighting at this link to play a part in documenting Singapore’s avifauna. We also strongly encourage you to make use of eBird for your day-to-day birding adventures.
Please let us know if you notice any errors! We will do our best to update the database as soon as possible and with proper acknowledgements.
Lastly, if you have any ideas for our database or the Singapore Birds Project, feel free to contact us!
All records submitted to our database will be reviewed by the Singapore Birds Project Record Committee. One key focus behind our integrated user submission system and database is transparency, because we believe in making all records and decisions publicly accessible. Given that sightings are shared across a variety of online platforms nowadays, we will continue to actively look out for records of rarities to prevent data from slipping through the cracks, while encouraging user submissions. We aim to cover all bases by being vigilant and using a future ready approach.
The birdwatching community in Singapore has been growing rapidly and everyone is yearning to learn more about our feathered friends. The Singapore Birds Project has filled in the niche for being a reliable source of updated and accurate bird information. This new database is a big step forward in our aim to contribute to the local community. We aim to update our database with more information and explore various avenues to utilise this data. We hope to continue doing our work, not alone, but as a community together with all of you.
Raghav Narayanswamy and Francis Yap: A massive thank you to the two of you for creating the digital platform to present our database in such an elegant manner. If not for your efforts, our work would have been constrained to a single excel spreadsheet.
Adrian Silas Tay, Goh Cheng Teng, Lester Tan, Martin Kennewell, Richard White, and See Toh Yew Wai: The feedback all of you provided when testing the initial stages of our database helped improve our public interface tremendously.
Elize Ng, Geraldine Lee, Movin Nyanasengeran, Sandra Chia, Tan Hui Zhen, Twang Fang Qi: Your reviews helped to greatly refine our overarching document that explains the processes behind our work. Thanks for your time in reading through 18 pages of texts. We will probably continue sending you all our future blog posts, so be prepared :p
Martin Kennewell: We are constantly blown away by how you take on the herculean task of curating Singapore’s eBird data with such precision. Your efforts over the past few years in promoting the use of this platform locally is finally paying dividends. Thank you so much for your work!
Bird Ecology Study Group, Lee Kong Chian Natural History Museum, Nature Society (Singapore) Bird Group, Oriental Bird Club: Efforts and publications by these organisations have served as key documentation for numerous historical records, to which we are grateful for.
The past and present administrators of key Facebook groups (Bird Sightings, Birder’s Group, Singapore Birders): Curating content on Facebook is not easy [I know, because I’ve recently become one of them! – Keita] and the efforts have allowed us to search for important information when compiling modern records. Thank you for your effort.
Every single person who has contributed to advancing the local ornithology scene over the past two centuries: Thank you, if not for the efforts of everybody who documented and shared their records, we would be living in a very different community today.
For much of my first few years of birding in Singapore, I wondered how the data from earlier eras in local ornithology could be made available for more to benefit; if early dates and late dates, major hotspots, past trends in the local avifauna, among other useful information, could be compiled in an accessible format for the community at large. After all, this small country has always been blessed with a higher-than-average observer coverage relative to its surrounding regions. The data could fill major gaps in understanding Asian avifauna, and be greatly beneficial to interested local birdwatchers as well.
So when I first saw that the Nature Society (Singapore) (NSS) had made its old editions of Singapore Avifauna from 1987 through 2010 available on its website, it was immediately clear that this could be a great resource for the birding community in Singapore if it could be consolidated into a more readily-accessible format. To really know how many times a species has been recorded locally, or which months it appears most frequently, manually scrolling through hundreds of reports for that species would not be practical. Rather, the data would need to be in a spreadsheet, and easily searchable, for the information to be most useful.
Recently, as Keita discussed last week, eBird has established itself as the most widely-used citizen science database for avian records. Many studies have referenced data stored in eBird to examine trends and achieve important conservation outcomes. It also reached a major milestone — 1 billion bird observations — in May this year, reinforcing its position as a powerful tool for conservationists and casual birders alike to share observations and further broaden our collective knowledge. It was clear to me that putting these important records from SINAV on eBird was the best way to make them as impactful as they can possibly be.
In collaboration with Singapore’s eBird reviewer Martin Kennewell, after obtaining permission from NSS to consolidate and upload the records, I set to work on designing a program to extract species names, observation counts, dates, and locations, as well as observer names for proper credit, for all the volumes of Singapore Avifauna available on the NSS website. Dividing this process into two steps: conversion of the PDFs (stored as images) into text, followed by extracting the important details from the text, I was able to upload over 27,000 individual observations, around 23,000 from Singapore and 4,000 from Malaysia and Indonesia.
The records uploaded now make up around 75% of all eBird records until 1990, and over 25% of all records until 2010 (the last year that Singapore Avifauna was published).
I can’t say that this journey was always smooth; one of the biggest challenges I faced was resolving old locations, with old place names, to current landmarks or points on the map which could be uploaded to eBird. With Martin’s expertise and support, I was able to resolve most of these, and sent a further few to NSS for their review. Additionally, some older editions of SINAV were missing; indeed, this was an era with limited technological access and keeping track of documents was admittedly more challenging than it has become today. Older records also suffered from a lack of specific counts; especially as birds that have now become rare once numbered in the dozens or even hundreds, observers sometimes may not have made the effort to accurately count these species.
See, for example, the entry for Sanderling in the report for February 1987.
This species is now barely an annual visitor; in the 80s, 90s, and even the early 21st century, counts in the double digits were regular. It’s hard to believe this count of 100 Sanderlings along with exceptional counts of other shorebirds, was just over 15 years ago.
Sometimes the work was tiring and it became difficult to continue, but I always knew the reward of making all these sightings accessible was worth the effort. In the end, after probably 100 hours of work, I uploaded the data to the NSS Records eBird account.
The excerpts below are from Volume 19 (Jan-Mar) of Singapore Avifauna, published in 2005 (link). I’ve used this example to highlight how the process of digitizing reports into individual records works. For January, February, and March of 2005, Blue-crowned Hanging-Parrots were recorded a total of 12 times. Since the report is split into each of the months, this species appears three times.
These three entries are then converted into text with optical character recognition and combined into one overall entry for the period covered by the report, in this case January to March:
BLUE-CROWNED HANGING-PARROT Loriculus galgulus
1 over Dairy Farm Road, 17/1 (LKS) and 18/1 (LKS) and 4 at Malcolm Park, 30/1 (NK/LKS/FR/IR/JR). At Botanic Gardens, 7 were counted on 4/2 (LKS) and 5 on 28/2 (AF/LKS). Also 3 over Nee Soon, 8/2 (LKS), 1 at MacRitchie Reservoir, 16/2 (LKS) and 28/2 (AF/LKS), and 1 over Dairy Farm Road, 24/2 (LKS). 1 heard at the foot of Bukit Timah, 12/3 (LKS), 1 flying over Dairy Farm Road, 22/3 (LKS) and 3 at Sime Road, 27/3 (LKS).
The individual records are then separated by looking for “sets” comprising the four important pieces of information for each record: count, date, location, and observer names. Of these, the most challenging to parse out is the location. In this case, there’s no extraneous information that we need to ignore, so it seems relatively straightforward to just use the leftover text as the location. But sometimes, sightings are associated with lengthy descriptions and the location needs to be extracted from that description – so I had to use natural language processing to pick out the location.
For the example above, the following 12 sightings would then be uploaded to eBird. This checklist shows how the first record (17 Jan) would appear in eBird’s outputs.
This project is mostly complete, and with it, thousands of bird observations recording hundreds of species have now been placed somewhere they can be accessed by researchers and amateurs alike. As more people come forward to contribute their sightings and share their knowledge, we can make more meaningful progress in conserving our valuable local wildlife.
This piece was written with the help of comments and advice from the Singapore Birds Project team (Dillen, Francis, Keita, Movin, and Sandra). My project drew on over a hundred reports made available by NSS on its website; their permission for me to take on this project also made this project possible. I also appreciate Martin’s contribution to many aspects of my project, including location-matching and manual approval/rejection of the uploaded records.
Sullivan, B. L., Aycrigg, J. L., Barry, J. H., Bonney, R. E., Bruns, N., Cooper, C. B., … Kelling, S. (2014). The eBird enterprise: An integrated approach to development and application of citizen science. Biological Conservation, 169, 31–40. doi:10.1016/j.biocon.2013.11.003
Sullivan, B. L., Wood, C. L., Iliff, M. J., Bonney, R. E., Fink, D., & Kelling, S. (2009). eBird: A citizen-based bird observation network in the biological sciences. Biological Conservation, 142(10), 2282–2292. https://doi.org/10.1016/j.biocon.2009.05.006