Birds have developed internal clocks that help them match their migration, breeding, feeding, and day-to-day routines to the changing rhythms of their surrounding environments. But are human activities having an impact on these patterns?
Tirth Vaishnav will receive his PhD in Ecology and Biodiversity from Te Herenga Waka in December. His thesis looks at how the behaviour and ecology of birds change over time, taking into account both natural shifts in the environment and the human impact.
Tirth says human activities—including climate change, the introduction of new species, increased use of air travel, and the growth of cities—are throwing the natural patterns of these bird behaviours out of balance.
His research takes a multi-pronged approach to the issue and covers four key areas which Tirth says emphasises the interconnectedness of natural and human environments at a macro level: bird strikes, pollination, kākā feeding, and nighttime activities.
“Bird collisions with aircraft are a serious concern for the aviation industry, and an increasing threat to human safety worldwide—I wanted to see if I could identify any patterns that could help mitigate bird strike,” says Tirth.
Using data from 122 airports across the globe, he aimed to understand if bird strike occurrences increased at certain times of the year.
“While seasonal trends weren’t apparent in the Southern Hemisphere, I could see that bird strikes were more seasonally concentrated in the Northern Hemisphere, and seemed to correspond with fledgling season and migration,” says Tirth.
“This aspect of my research will hopefully be helpful for airports when developing strategies to deal with wildlife hazards.”
For the next part of his thesis, Tirth looked much more locally: Zealandia ecosanctuary. He examined data collected over nine years showing how birds visit flowers and fruit.
“The birds in New Zealand act as both pollinators and seed dispersers for plants, so it was interesting to find out exactly how and when they interacted with flowers and fruits differently,” says Tirth. “Flower and fruit visitation peaked at opposite times of the year, in spring and autumn, respectively. Birds used different seasonal strategies for visiting flowers and fruits of various plant species.”
Kākā then became of particular interest to Tirth, because they are known to have adapted their feeding patterns to include non-native plants.
“Kākā are known to switch their food resources seasonally as they become available. I looked at their seasonal foraging patterns on native food resources, as well as on pine seeds, which are available year-round. I found that they are opportunistic feeders and they have a lot of dietary plasticity to include these new resources in their diet,” says Tirth.
“In terms of conservation management, and as kākā disperse further into urban areas, it does raise the question of whether pines are good or bad for them—they’re a good food source if native species aren’t abundant, but you don’t want kākā to lose out on that natural behaviour where they switch resources seasonally. It’s definitely something for conservationists to consider in restoration planning.”
The final phase of his research again focused on kākā, and their nighttime behaviour patterns. Kākā are a notoriously noisy bird, with their loud screeches reverberating throughout the night around the valleys of Te Whanganui-a-Tara. Tirth wanted to find out what exactly they were getting up to at night, and how that differed from their daytime behaviour.
Tirth found the kākā is a bit of an outlier among parrots, being among a handful of its kind known to be active during the day and night. The vast majority of parrots around the world are diurnal (active during the day), and just two species worldwide (including Aotearoa’s very own kākāpō) are nocturnal.
“Kākā behaviour was known in Mātauranga Māori, but the details have been lost post-colonisation. My findings show what is, to my knowledge, the first detailed scientific account of partial nocturnality in a parrot species,” says Tirth. “While the light and noise of urbanisation may be a factor, I looked at kākā in Zealandia, which—as a relatively dark and quiet environment—is more reflective of their native habitat. But I could still see that they foraged more during the day and moved around more at night.”
Coming from Mumbai, Tirth wasn’t initially a bird researcher, with his Masters focused on a wildlife corridor for tigers, leopards, and bears, but the influence of island biogeographer Professor Kevin Burns changed that.
“Coming to Wellington opened up the avenue of researching birds and their ecology and behaviour, which is something that I never anticipated even five years ago.”
Tirth says that on a big picture scale, understanding the impact of time and seasons is important.
“We are starting to see these temporal patterns shift as climate change gets worse. As disturbances like this, along with the effects of urbanisation on habitats, continue to alter the timing of natural events on a large scale, it’s increasingly crucial to understand how that affects the way birds behave and interact with their environments.”