It’s been a month of excitement, upheaval, and some head-scratching for birders and ornithologists across the globe. What’s been going on? Why have feathers been ruffled? Why are people posting updates to their Singapore bird lists?

The source of this consternation has been the publication of a new avian checklist named AviList, which BirdSoc SG now follows as of the latest checklist revision. This new list summarizes all avian species across the world, and as of its launch documents 11,131 bird species (of which 430 have been recorded in Singapore). The publication of this list was the result of meticulous hard work by a committee of ornithologists, who worked hard on building a consensus between multiple previously published global bird lists.

Let’s back up for a minute here. Many birders may be wondering why this is a big deal, or why so much work is required to generate such a list – after all, don’t we know all the different bird species on the planet already?

The answer is not so simple, and is linked to a field of scientific study known as taxonomy.

Taxonomy is the classification of organisms into different categories. It provides us with a framework for understanding the natural world around us, and was developed in the 18th century by the botanist Carl Linnaeus. Higher categories include broader divisions – for example, plants and animals are two such divisions (representing ‘kingdoms’), whereas mid-level divisions may refer to differentiating mammals and birds (representing ‘classes’). Lower level divisions represent differentiating between species and subspecies.

Defining what exactly a species is both intuitive and complicated. Intuitively, you could look at a White-bellied Sea-eagle and a Brahminy Kite and instantly recognize them as different species. How about a Blue-winged Pitta and a Mangrove Pitta? They look somewhat similar superficially, but you can find noticeable differences between the two which would probably convince you that they are different species (they occupy different habitats, their bills look different etc).

What about Cook’s Swift and Pacific Swift?

As you may be realizing, it’s not always very straightforward to define what exactly a species is. And therein lies the source of the problem.

Bird watching is a popular hobby, and this led multiple different organizations and enthusiastic ornithologists to come up with lists of all bird species recorded on the planet. You may already be familiar with or have come across these different lists: BirdLife has their own list, as does eBird (based on the Clements Checklist), and so does the IOC (International Ornithological Congress). We here at BirdSoc SG have been following the checklist by IOC. There is broad consensus across these checklists and they generally recognize the same species; however in trickier cases (for example the example of swifts above), they have reached different conclusions regarding whether a particular ‘taxon’ (i.e. a low level division) is a species or not.

This led to some confusion and problems for end-users. For individual bird-watchers, it could cause uncertainty on whether something you have photographed is a new species or not (for some time, Kentish and White-faced Plover were split into two species in our Singapore Bird List, but not on eBird). For legislation, this is also problematic: if you work for a conservation organization and are trying to determine whether a species is worth protecting, it would be really helpful to understand whether it actually is range-restricted, or whether it’s widespread and therefore you should save your conservation funds for another more deserving species.

AviList was born out of an effort to harmonize major avian global checklists, and to build a consensus which removes such discrepancies. In particular, they recruited ornithological experts from across the globe, including those ones involved in creating/maintaining the multiple conflicting lists (BirdLife, eBird/Clements, Avibase and IOC), and formed a large taxonomic committee. The committee proceeded to identify over 1,000 cases where there was a discrepancy between the different checklists, and then discussed each case in detail and finally voted on whether the taxon in question should be regarded as a species or subspecies. This effort took over five years, and we are seeing the fruits of that labour this month with the publication of AviList.

So what happens to all the other lists and their websites? Well, fear not! Most of them are already 99% aligned with the decisions made by AviList (since they were already involved in creating AviList), so they will continue to update until they are fully aligned and then cease publishing new lists. BirdLife will take a bit longer than the rest to fully align – this is because BirdLife is a conservation organization which assesses population status etc of the various species which it lists, therefore completing this alignment will require a lot more hard work and effort on their end.

You can check out this Spotify https://open.spotify.com/show/09iGFnxdKygOuCYRN93Obd to hear some behind-the-scenes story directly from some of the AviList curators.