Dr David Vieco Galvez at home during the COVID-19 lockdown.
International PhD candidate David Vieco Galvez has graduated from the School of Agriculture and Environment this week after spending more than four years studying the reproductive biology of the genus Apteryx, which includes the five species of native kiwi.
Dr Vieco’s research took him around New Zealand where he analysed kiwi eggshells and extracted DNA from eggshell membranes. He was able to determine that kiwi chicks in a nest are not always siblings, suggesting a non-monogamous mating system, which contradicts the previously- held theory that kiwi mate for life.
Before coming to New Zealand, Dr Vieco studied the flocking behaviour of birds in the Andes of Colombia, where he also met his Massey supervisor, Associate Professor Isabel Castro, at an ornithological conference. Dr Castro introduced him to the possibility of studying kiwi.
“I always was interested in the Apteryx (kiwi) species, because it’s one of the most unusual bird species there is. If you look at it, it looks much more like a mammal than a bird, so I was thrilled to be able to see these animals in the wild and in real life,” he says.
Dr Vieco with a kiwi on Ponui Island.
Because kiwi are such an unusual species, studying them can reveal more about different bird species in general, according to Dr Vieco. “When we make comparisons between bird species it is very important to understand the species that deviate from the norm. Those unusual species can tell us a lot about evolutionary pressures that have shaped how they are today.”
To get access to kiwi eggshells, Dr Vieco worked with Operation Nest Egg (ONE) who supplied him with hundreds of samples from all over New Zealand. ONE is a programme that incubates wild laid eggs in captivity, which allowed Dr Vieco to look further into the reproductive biology of the species in a non-invasive way.
“One of the biggest difficulties while studying kiwis is that we cannot disturb the birds, which is absolutely fundamental in studying any endangered species. So, fortunately, ONE collected all the eggshells after they had reared and released the chicks, which allowed me to have a look at different times and different locations the different properties of the eggshells,” he says.
Dr Vieco’s research looked at the physical characteristics of kiwi eggshells to see how they were adapted to their environment, and focused on brown kiwi, to look at how those characteristics fit with the nest architecture. He also looked at the mating systems of the different species, and ended up focusing on brown kiwi because they are the better-known species and had the best samples.
“I extracted DNA from the membranes of the eggs and eggshells to see if all of the chicks that hatched in a nest are all siblings or not. And it turned out they were not.”
Some of the chicks in the nests Dr Vieco studied were related, some as full siblings, some half-siblings, meaning that they shared either the mother or the father, and others were completely unrelated, confirming that kiwi are not monogamous.
“It was widely believed that kiwi mate for life, but that's definitely not the case. Kiwi are somewhat closely related to ostriches, emus, and cassowaries, and these other species all have mating systems similar to polygamy or promiscuity where males mate with several females sequentially, and females mate with several males. If kiwi were monogamous, that would be an important evolutionary jump, but it seem unlikely to be the case, based on the behaviour of the related species,” he says.
Studying kiwi in the wild
He carried his fieldwork out on Ponui Island, a small private island in the Hauraki Gulf and the base of Dr Castro’s research programme. “Ponui Island has a thriving population of around 2000 brown kiwi and that was the perfect scenario for me to study their nest architecture, as these birds have been radio-tagged and followed for about 20 years.”
There, Dr Vieco conducted a series of experiments to test the insulation capacity of the nests, to describe how they're built and to test the lining materials without disturbing the birds, finding that the nests maintain higher temperatures than those of the environment at night while the incubating parent is foraging.
He found that eggshells presented capped and plugged pores, and are more porous than previously measured, which changes the way their gas conductance in a burrow nest is understood.
Another discovery was that the cuticle (the external part of the eggshell) is composed of triangular crystalline particles that are only shared with an extinct therapod, a velociraptor type of dinosaur. “At this point, we don't know the purpose of this cuticle but it's interesting to find a coincidence with an extinct animal which is, in principle, quite distant to the kiwi.”
Dr Vieco says finishing his PhD has not quite sunk in. “It feels unreal – it hasn't sunk in yet that I am to officially become a doctor. I think it will take time before it properly sinks in but it's very exciting and I'm really happy that it has come to a good end.”
Coming from Medellin, a city of six million people in Colombia to Palmerston North’s 180,000 was a shock at first, but he says he enjoyed his time there. “I really liked it. I discovered the charm of Palmerston North and made really good friends and really enjoyed it. I was very supported by all my supervisors but especially Professor Patrick Morel who funded a big part of the research, which I'm incredibly thankful for,” he says.
Dr Vieco says he’s glad to be in New Zealand during the global pandemic. “I'm very grateful for what the government has done to manage this pandemic. My visa was going to expire in May this year, but it has been extended to September to allow us to sort our lives out in the meantime. This country has become an example internationally of how to manage the pandemic and I'm incredibly happy to be here.”