The Most Ancient Passerine

Imagine that the earliest human was still alive - what would it be like to communicate with them? Would they grunt and whistle? When we start talking to them, using the words we know so well, would they listen and learn to speak like us even though their brains are different?

Within the Passerine clade, more than 6000 species of birds sing intricate and powerful songs. They were grouped in the Passeriformes based on the structure of their toes (three front, one back), making perching on tree branches and singing from them a thing. Around two thirds of these perching birds are called oscines and have the ability to learn their songs, just like how humans learn our mother tongue. To pull off the perfect song as a learning songbird, they take their time to listen as a baby and follow the footsteps of their parents. They start off with singing off tune, and adding extra meaningless words, not really knowing what they’re doing. Slowly, they get the rhythm and the melody right, and they graduate music school and go on to the world of sounds to pursue their lifelong career of driving ornithologists out of bed in the morning!

Anyway, this wonderful skill of vocal learning is a rare trait in the animal kingdom. In addition to birds, only a handful of land and sea mammals can do it. Humans are one of them, along with whales, dolphins, bats, elephants, seals, and three clades of birds, which are the parrots, oscine songbirds and hummingbirds. These three bird groups were very distantly related, so it was commonly understood that their vocal learning ability originated independently.

Now, what if I told you that the most ancient Passerine is still alive today? And has been since millions of years ago? I am talking about the Passerine suborder Acanthisitti. They are also known as New Zealand Wrens because they are only found in New Zealand (which, mind you, is a hub for birds that don’t follow bird rules). The Acanthisitti is ancestry to all songbirds! How did that happen?

There has been a long debate of where the New Zealand Wrens belong in the avian family tree. They were placed within the suboscine, which are non-learning songbirds within the Passerine order. But in 2014, there was finally a consensus that they actually have no close relatives. And so they were removed from the suboscines and placed as their very own suborder, consisting of the Rock Wren (Xenicus gilviventris) and Rifleman (Acanthisitta chloris). Not only that, they are now also a sister clade to parrots!

In this new avian family tree, the New Zealand Wrens form an important link between the two most prolific vocal learners in the world of birds, the parrots and oscine songbirds. Sandwiched between these two groups, their vocal abilities and brain structure spark the interest of ornithologists and neuroscientists the world over. If they could learn their calls, then there may be only two origins of vocal learning in birds instead of three!

In a sub-montane forest in the North Island of New Zealand, I am part of a small team of Rifleman researchers. I record and observe the vocal development and call functions of the Rifleman (Maori name: Tītipounamu) to see if they follow the pattern of vocal learners. These two species don’t have songs per se, just simple high-pitched calls, says all bird guides and online references. But I beg to differ. A closer look at the Rifleman repertoire revealed that their calls are complex and flexible. How long does it take to vocally mature? Can the Rifleman learn their calls and pass down their language legacy? And how does it compare to the vocal learning ability in oscines and suboscines? If vocal learning exists in the New Zealand Wrens, what would it mean for our understanding of the origins of vocal learning in birds? In two years while we complete our PhD, we will start to have answers to these important questions. Following the lives of the tiniest bird in New Zealand and the most ancient Passerine as an early career ornithologist is very rewarding indeed!