How do you survive by being small? The soundscape in a New Zealand bush is filled with splendor. But among the powerful song and majestic plumage, there is a niche for all things small and sweet. In Boundary Stream Mainland Island, a forest reserve in the Hawke’s Bay region, a group of tiny birds constantly flick and flutter in the trees; tomtits, grey warblers, silvereyes, robins…and the smallest of them all is the tītipounamu (Acanthisitta chloris), dubbed rifleman due to their army-like plumage. The male is bright green and the female has beautiful shades of brown. And both sexes have white underparts. They are so small that a wing flap of a butterfly could be mistaken as a tītipounamu. Not only that. They are also very difficult to hear because they are so high pitched. And because of that, many don’t notice them among the tūī, bellbirds, and kākā. I spent the first week of my fieldwork season tuning in to the high pitch calls of the tītipounamu, tilting my head this way and that, like an owl, to pick up subtle wisps of conversation between foraging pairs. After some practice, I could finally tease apart the calls between tītipounamu, grey warblers and tomtits, by their small differences in pitch and length.
Genetics research in the past decade have plucked the tītipounamu from the suboscine group and placed them as a link between the passerines and the parrots. That challenged many assumptions about birds that sing (songbirds/oscines) and those that don’t have a song (suboscines), such as when did vocal learning appear or disappear in the evolutionary pathways of birds? So here we are, trying to decipher their potential hidden skill of vocal learning in this special species. Could they be learners? Well, we know that they are not songbirds, because they don’t actively defend their territories by singing, and they have cooperative breeding behavior. It was found that they have slight variations in their calls across the North Island populations. And they use their calls different in so many different contexts (more on that later). My work here is to look at how long it takes for a juvenile tītipounamu to acquire the adult voice. Vocal learners tend to take a longer time to mature vocally and start singing their song, and non-learners tend to take no time at all. I will also look at the functions of each of the juvenile and adult calls, something that hasn’t been well documented before.
In this 8-part series of short blog posts, I will take you through the life of the smallest bird in New Zealand. And in little snippets, I will also reveal the challenges and triumphs of being a wildlife field biologist and a PhD student. Check back in this space every Monday, Wednesday, and Friday this month for more! This series is also an upgrade and an extension of my first post about tītipounamu field work published in Ecology Ngātahi at the beginning of my fieldwork season. Since then, I have stayed 5 months in this forest recording the sounds of this bird, following them to their nests, spending hours at the nests recording their breeding behaviour, and straining my neck looking up at the fledglings. This is the longest I have ever been in a forest, walking the paths more than a hundred times, watching it grow, and seeing it in many different lights. I have travelled 8,900km to this country to learn about the interesting vocal behaviour of this bird. Truth be told, there is so much to learn wherever we go. And it led me here to this beautiful land of unique bird life. Being surrounded by the soundscape of this forest and the wonderful team that I’m working with, I am glad this is where I will spend all the summers of my PhD doing fieldwork!
The next blog post will be up on the 4th of February 2019, please stay tuned!
Next post: Nest building