Burgess bird research - the physiology of diving petrels

I’m used to sitting in the dirt, in the dark, to work with seabirds. To be sitting around a table in the well-lit bunkhouse on Burgess Island with a diving petrel in my lap is a somewhat different experience.

On one side of me, Auckland Museum’s Matt Rayner and Auckland Council’s Todd Landers are banding the birds as they bring them in. I get handed a diving petrel in a bag, weigh it, and take a blood sample. On my right, University of Auckland’s Brendon Dunphy is processing the samples as I hand them over, steadily pipetting and centrifuging. At the other end of the table, Abby McBride, sketchbiologist extraordinaire, is taking notes on the little production line we have going on.

We’re here to do an annual health check-up on the diving petrels - taking weight measurements and small blood samples to get an idea of how the population is faring. For the past 4 years, Brendon has been keeping an eye on the diving petrels on the Mokohinau Islands. By taking measures of body condition annually, he has been tracking how the population responds to environmental fluctuations.

Diving petrel and egg - Photo by Abby McBride

Seabirds are particularly sensitive to alterations in sea-surface temperature such as the El Niño Southern Oscillation (ENSO), which causes shifts in productivity in the Pacific Ocean. This means that the prey species that seabirds feed on can be in completely different places from year to year. They may have to travel further to feed in some years than others, which can impact their breeding success.

Over the past two years, we have experienced strong warm El Niño conditions, and the weights of diving petrels has been dropping. This change has also been reflected in their physiology, with blood cell parameters indicating that the birds may be nutritionally stressed – they’re potentially not finding enough to eat. With a rapidly warming climate, knowing how these birds respond to environmental change is vital in predicting how they’ll cope – and what needs to be done to conserve them.

The Mokohinau Islands are a seabird hotspot in the Hauraki Gulf, with a total of 9 species breeding on Burgess alone. It’s the perfect place for a bunch of seabird researchers to spend time gathering information on how these populations are doing. During our short two days on the island, we check nest-boxes and burrows, take measurements from Grey-faced petrel chicks, attempt to retrieve geolocators from storm-petrels (no luck!) and set up acoustic monitoring stations. We also do a fair amount of swimming in the chill spring sea!

Taking measurements from a Grey-faced petrel chick - photo by Brendon Dunphy

The next night we’re perched on top of a cliff overhanging the ocean. As the sun vanishes, the deep haze of dusk creeps across the sky and shadows begin to soar overhead. The tell-tale whistle of Grey-faced petrels, a chatter of White-faced storm petrels, and the curious purr of Northern diving petrels begins to fill the air.

All of a sudden we’re caught in a whirlwind of seabirds returning to their burrows. I’m hopping over rocks to lift diving petrels out of the grass, the ghostly flashes of White-faced storm petrels caught in the light of my headlamp. The world narrows to its glowing beam and the tiny bird in my hands, while the darkness is a-whirr with wings and the chorus of hundreds of petrels, the steady breath of the sea a few hundred meters below. This is more the seabird science that I’m used to, but at a scale that I’ve never experienced before. Burgess Island is overflowing with birdlife.

The data we gathered this year is positive. With more neutral ENSO conditions, the weight of the diving petrels is increasing again, and their blood physiology is back to normal. Long term monitoring of seabird physiology gives us an important insight into how environmental changes impact on seabirds ability to raise chicks. It’s also much easier than monitoring breeding success directly, which requires months of checking on incubating birds, chicks, and then seeing how many fledge. It’s science on a shoestring budget – quick trips and tiny samples yielding a significant amount of information on which we can make more informed conservation decisions.

Our time on Burgess is brief, but we come away with important data, having shared the amazing experience that is one of the Hauraki Gulf’s most remote islands – a pest-free haven for ever-growing numbers of seabirds.