The Australian magpie has been crowned bird of the year but how much do we really know about it? Where do magpies fit in the evolutionary scheme of things? Why do we even call them magpies?
DNA sequencing technology has revolutionised biology. Our understanding of the evolutionary tree of bird life – that is how species and groups of birds are related to each other and how their evolution has unfolded on the planet’s changing continents – is no exception. We now have a much better understanding than we did just 30 years ago of where all the species of the world’s birds perch, so to speak, on that tree.
We now know that Australian magpies are an evolutionary radiation of several thousand species of songbirds, which are more strictly known as oscine passerines. Our current understanding of their evolution is that the origins of songbirds were here in Australia.
Evolution of the different kinds of today’s songbirds began about 34 to 24m years ago. Its rate quickened 24 to 5m years ago coincident with extensive island formation in that part of present-day Indonesia biologists call Wallacea. That provided the first dispersal corridor out of Australia. It led to waves of songbird expansion and evolution through Asia to the rest of the globe.
Now consider that European ornithologists knew about and named their birds well before they learned about Australia’s avian riches. The name magpie, therefore, was first assigned to European birds that we now know to be more closely related to crows. As far as I know, it was bestowed upon the Australian magpie largely on the basis of the black and white plumage so broadly similar to the Eurasian magpie Pica pica. Australian magpies, along with so many of Australia’s other familiar land birds that were also named after European namesakes (think of treecreepers, shrike-thrushes, magpie-larks, quail-thrushes, fairywrens, and so on), actually show us how the ancestral stocks of the oldest songbirds evolved after staying right here in Australia.
We know from research led by Anna Kearns when at the University of Queensland that magpies are most closely related to several other groups of birds that will be familiar to many people in Australia, most notably the butcherbirds and the currawongs. Most simply, Australian magpies are butcherbirds that have evolved a much more terrestrial way of life than the other butcherbirds. Therein lies the reason I have not yet mentioned the scientific name for the Australian magpie.
Scientific nomenclature places groups of closely related into species into genera (singular: genus). So the generic names we use change as knowledge of relationships is tested and refined. Given that we are now confident that butcherbirds and the Australian magpie are all more closely related to one another than to any other group of birds, it is simple and expedient to assign them all to one genus, Cracticus. Within Cracticus, as within any genus, each member species of butcherbird has its own distinguishing species-level name. Australian magpies, remembering that they are terrestrial butcherbirds, would become Cracticus tibicen. Simple, right?
Yet Australian magpies are plainly very distinctive, both in the ways we come to know them as daily parts of our lives and even in more technical traits that ornithologists discuss, such as the patterning of their eggs and their DNA sequences. Simply because of their distinctiveness to us (and we are very visual creatures), Australian magpies have long been placed in their own genus, Gymnorhina, where they have been the only species and known as Gymnorhina tibicen.
The twist that recent research brings to the discussion is that one other species of butcherbird, the black butcherbird, a truly all black-plumaged bird, is more closely related to the Australian magpie than it is to the half dozen or so species of butcherbirds. That is where it gets tricky. It remains perfectly valid to continue recognising all in Cracticus.
If we want to use scientific nomenclature to recognise all of the Australian magpie’s distinctive traits, which have endeared it to almost 20,000 Guardian voters, and place it in Gymnorhina, then the black butcherbird has to enter the picture. Either we assign the black butcherbird to Gymnorhina too, or we place the black butcherbird in its own, third genus, which happens to be Melloria.
The pendulum of our understanding is swinging to this latter approach of recognising three genera for the butcherbirds and the Australian magpie. Although I was an author of the research back in 2013 that advocated Cracticus for all, we live in a democracy and I was out-voted by my co-authors when it came to keeping Gymnorhina.
- Leo Joseph is the director of the Australian National Wildlife Collection at the CSIRO