Seabirds are the ecosystem drivers of islands, traversing the marine-terrestrial interface throughout their lives. In particular, they transport marine nutrients from the ocean to islands, which they ‘deposit’ while burrowing and nesting. These nutrient inputs have driven island ecosystems for thousands of years, and did not go unnoticed by our forefathers through such actions as the Guano Islands Act. Today, seabirds across the world are threatened with extinction, but one species in New Zealand is not at immediate risk. The grey-faced petrel (Pterodroma macroptera gouldii), which is a sub-species of IUCN ‘Least Concern’, numbering in the hundreds of thousands and found throughout the upper north island of New Zealand.
An oddity among its relatives, the grey-faced petrel is a winter-breeder, so its chicks fledge at the height of summer. So in April each year, grey-faced petrel return to their New Zealand breeding sites for nothing less than a breeding frenzy of birds cackling across the surface. Unfortunately, it is precisely this period when they are most vulnerable to predation by medium-sized carnivores such as cats and dogs. Although the grey-faced petrel is in high abundance, this is only at a few of its remote island breeding sites. At many other small island and a few mainland headland breeding sites, the number of birds is dwindling. This imminent extirpation will see the loss of this keystone ecosystem engineer from these sites. It is for this reason that my research group is so interested in studying and conserving grey-faced petrel across their range.
This year, during the breeding frenzy, we visited two contrasting mainland sites on the West coast of Auckland, where we suspect the birds do better due to their proximity to the Tasman Sea. At one site, local rangers started pest control eight years ago and today there were over 60 birds in the space of a few hours, mostly unbanded birds suggesting colony recruitment, although a few birds found banded from a neighbouring island colony also suggest migration between sites is more important than previously thought. However, at the other site the colony had not been monitored for 20 years. Here (after hours scrambling through inaccessible scrub), we found only a few birds clinging on to cliff edges. Unfortunately without pest control this latter site is now just a mainland wreckage colony. Over the rest of the breeding season we will continue to monitor the birds here and on key small island sites to measure chick growth and health, before they finally fledge for a Happy New Year!