Burrowing Bird Getting a Boost

One reason why I love working at the San Diego Zoo Institute for Conservation Research is that I can do both lab and field research. For the last 12 years I have studied a very interesting bird, the kiwi. Kiwis are endemic to New Zealand, and even though it is the country’s national icon, few are seen in the wild. 

Unfortunately kiwis are in decline, as often happens to species of isolated island ecosystems into which mammals are introduced. Species that evolve without the presence of mammalian predators do not exhibit proper anti-predator responses, meaning they don’t run for their lives when the situation arises. Currently, the main challenges to kiwis are predation of chicks by stoats (a type of mink).

In the last 19 months, postdoctoral fellow Sarah Jamieson, has radio-tagged 47 adult kiwis. We documented 41 nest-burrows, explored the importance of habitat quality, and parent behavior on chick survival. In October I went to New Zealand to spend two weeks with Sarah and her field assistants at our field site, which is isolated despite its proximity to Auckland. 

Following the 12-hour flight from Los Angeles we drove for an hour, picked up two weeks worth of food and supplies, and took a 15-minute boat ride to the field site.  Because we are on an island, all necessities must be brought along—there is no popping down to the store to pickup a loaf of bread or roll of toilet paper. Although remote, our site is not primitive; it is located on a working ranch, with a small cabin and an outhouse, which is preferable to a tent and a shovel. 

Burrowing Into Field Work

The typical kiwi research day begins with a one-mile hike to the gullies where our kiwis reside. This may sound easy, but the hills are very steep and plentiful, there are cattle (and cow pies), and the equipment for tracking and measuring the birds, our water, lunch, and snacks for the day are all strapped to our backs. I received no special treatment from Sarah and the crew. Sarah has alternated two weeks on the island and two weeks at Massey University, for the last 2 years.

Once at our kiwi gully I had to find the kiwi sleeping burrows, which is easy because they are marked, or so Sarah said. 

Unfortunately the marker tape is green, not a color that stands out in lush New Zealand forest, and the GPS is little help beneath the dense canopy.  By the time I managed to find a burrow, I was so excited that I barely noticed the 500 kiwi ticks clinging to my hands after measuring burrow parameters and placement of tick traps. 

In the afternoon, back at the cabin, everyone gathers to go over the radio tracking information. Basically this is when we find out which kiwi was in which nest-burrow with who, a veritable “who is in who’s nest-burrow with whom” soap opera. Who needs TV? 

After dark, it is back out the one-mile hike over multiple hills (and cow pies) to check on eggs being incubated. Because kiwis are nocturnal and we do not want to disturb the incubating male, we have to wait until he leaves the nest-burrow to feed and guard his female. 

As we wait for the male to leave, I have time to enjoy the spectacular vision of New Zealand glow-worms on a stream overhang. These little larvae of a fungus gnat glow to attract prey that they catch using long sticky threads.

There is little doubt when the male kiwi leaves the burrow, and we can use our radio tracking equipment or just listen as he crashes through the forest undergrowth. Although kiwis are beautiful and interesting to study, they are neither quiet nor graceful birds. Getting our hands on the egg is important for egg measurements and a hatch date estimate. Knowing the hatch date is imperative to catching chicks for radio transmitter attachment, which will allow us to investigate parental care and chick dispersal.

Each day we do our field work chores: radio tracking the birds, kiwi burrow parameter measurements, tracking down a kiwi chick for growth measurement, or watching the Rugby World Cup tournament (which New Zealand won, of course).  What an exhilarating week!

Tom Jensen, Ph.D., scientist, San Diego Zoo Institute for Conservation Research.