Te Papa vertebrate curator Dr Colin Miskelly recently spent 12 days on Ohinau Island (east of Whitianga, Coromandel Peninsula) as part of a Te Papa seabird research team. This blog reports on what the team found living underground on the island.
As described in previous blogs in this series, a burrowscope is a high-tech tool used to view the contents of burrows, and is similar in design and function to an over-sized endoscope. We used a burrowscope every day as part of our research on flesh-footed shearwaters.
Within the main study colony, 54 adult flesh-footed shearwaters had been fitted with tracking devices (see previous blog). Each tagged adult was marked with white correction fluid on its head, allowing us to identify when a tagged bird had returned from the sea without having to handle the bird. Such birds were then extracted from their burrows and the tracking device removed, so that its data could be down-loaded.
During population estimates of each sub-colony we defined the sub-colony perimeter, counted burrow entrances along transects within the sub-colony, then burrowscoped at least 30 burrows to determine whether they were occupied by flesh-footed shearwaters or their eggs (which are occasionally left unattended during the day). This allowed an estimate of the number of occupied burrows per sub-colony.
Flesh-footed shearwater eggs began to hatch about 27 January, and within a few days the downy chicks were left unguarded in their burrows, while both parents foraged at sea.
Few other burrow-nesting seabirds were present on Ohinau Island at the time of our visit, having completed their breeding season (see Seabirds of Ohinau Island). However, we found one moulting little penguin in a burrow on the main island, and a couple of failed fluttering shearwater eggs in burrows on an offshore stack.
We did find a few fully-grown fluttering shearwater chicks still in burrows during a brief visit to nearby Ohinau-iti Island on 24 January.
The most surprising discovery that we made with the burrowscope on Ohinau Island was a tusked weta. These endangered insects were introduced to Ohinau Island in 2007 (see Critters of Ohinau Island). They are night-active, and most are presumed to hide in their own small burrows during the daytime. While checking a small bird burrow under forest on Ohinau Island (hoping to find an occupied Pycroft’s petrel burrow), we were delighted to see the distinctive form of a large adult tusked weta.
With thanks to Ngati Hei for permission to visit Ohinau, and DOC for logistic support. Robyn Blyth, Lizzy Crotty and Liam Miskelly assisted with field work during my visit.
Other blogs in this series