The value of a zero count

Consider two different birding sites. In one, we have no idea whether a particular species lives there or not because no birdwatchers visit. In another, we can infer that that particular species probably doesn’t live there because birdwatchers frequent the site yet fail to find it. Accurate data telling us that a bird is missing is often as important as accurate data telling us that another species of bird is present. We explore the importance of such information in this article.

We live in a society that is increasingly data driven. It’s overwhelming how much information is out there and one of the major challenges is setting the right filters so we can see what we are looking for. A quick look at eBird data for Singapore at the time of writing (8 March 2025) shows that there are over 88,000 checklists. If there were an average of 12 records per checklist, this would mean there are a million records in this dataset. Some of the over 88,000 checklists are accompanied by photographs that provide additional quality to the data reported. Are you able to find birds hiding in these pictures? If we are looking for the answer to a question, how do we go about this? Fortunately, eBird data can be downloaded and analysed by those talented enough (not me). There are some more manual ways to check the information, but it takes time. While examining this valuable wealth of data, there’s an important caveat to bear in mind. It’s entirely based on the presence of birds, not on their absence. When submitting an eBird checklist there is a specific box to check to state whether this is a complete checklist or not i.e. all species observed are recorded. But should a complete checklist include species that should have been seen but were not, such as a target species that was not found. It’s easy to get silly about this – of course we’re not going to go out on a daily basis and record every species that we don’t see. But somewhere between the recording everything that we see and recording everything we don’t; I would argue that there is a valuable point about the value of a zero count. Why would we care about a zero count? Primarily, those with a strong conservation interest will be looking to highlight scarce and declining species. Anyone chasing a year list is also acutely aware of what is missing or getting harder to find on an annual basis. I see it as one role of the Bird Society of Singapore to draw attention to trends in local bird populations, hence this article. One thing that eBird data does allow for quickly and easily is to check when a species was last seen. To look at Singapore, the first wild species on this list is a Brown Booby from 1878. There’s then many other species that have not been recently recorded, not entirely comprised of vagrants but also including some former breeding species such as Moustached babbler and Crimson-winged woodpecker. To look more recently, from 2015 onwards, here’s a quick run through of some of the species that have changed their status and may be considered going; or gone: Little Grebe IUCN Least Concern Until around 2021 this species was regularly recorded from ponds in the Punggol area. However, this species became locally extinct there. The species still occurs occasionally, and has been known to breed in the past. There are well founded rumours of a small population on a pond on the inaccessible Jurong Island. Otherwise, the most recent record was single seen on Pulau Ubin in January 2025. Little Grebe at Lorong Halus Wandering Whistling Duck Least concern A small number of this species was regularly recorded at the Eco Lake in Singapore Botanic Gardens until December 2016. The birds were no doubt escapees from a local waterfowl collection. Since then there have been no further records and it seems unlikely that any genuine vagrants will occur. Wandering Whistling Duck, Singapore. One of the last few birds from the introduced population Grey-headed Swamphen IUCN Least Concern Formerly a regular, if difficult to observe, resident of Kranji Marshes this species was last recorded in May 2018. The elevation of this location to a nature reserve in 2016 appears to have not benefited this species. Grey-headed Swamphen at Kranji Marsh Grey-tailed Tattler IUCN Least Concern Formerly a regular at sites like Sungei Buloh this species was last recorded in August 2021 at Pulau Tekong, and the last “publicly available” bird was January 2019 on Ubin. The decline of this species is no doubt linked to the wider decline of shorebird populations within the East Asian Australasian Flyway and it seems likely that other shorebirds will share the same fate. Grey-tailed Tattler at SBWR Black-crested Bulbul IUCN Least Concern This species was regular at the summit of Bukit Timah summit in the past but recent sightings are scarcer, with the last on eBird from 10 June 2024. The species has been recorded occasionally since then at other locations in Singapore, such as a single at Chek Jawa in June 2024. As with Wandering whistling duck, this species is introduced to Singapore. Black-crested Bulbul at Bukit Timah Black-headed Bulbul IUCN Least Concern This species was formerly regular in the Central Catchment Nature Reserve, but has not been recorded there since October 2022. The species has been recorded occasionally since then at other locations in Singapore. Black-headed Bulbul at Jelutong Tower Lesser Green Leafbird IUCN Near Threatened Until 2017 this species was regularly...