Seabirds – Predators of the Open Ocean
Vol.7. 21st June 2017
Guest post by Julie Miller, University of Glasgow
Julie Miller is a PhD student at the University of Glasgow studying population dynamics of seabird species and their vulnerability to extinction.
One of the focuses of this research expedition is to collect data on marine predators in the region. Seabirds are apex marine predators; with many species covering broad ranges, information such as their presence in the area, life stage, morphology and their behaviour may give us an indication of where these birds have come from, what they are doing here and indicate more information about the wider ecosystem. To complement our continuous transect surveys, documenting abundances and distributions, we are beginning to try and catch the birds to gather more information on diet, morphology and to deploy loggers to track some individuals.
Birdwatching © Marguerite Tarzia
Rising to the bait
After bouncy seas delayed us, we made it to the start of our catching transects. As you read in an earlier blog post, we have several bait lures to try to attract our seabirds. Being long range predators of the open ocean, many seabirds utilise olfaction (scent) to find food in this vast expanse. We have three main stinky fish lures to attract them. The big chum blocks, tethered to the back of the ship; slow leaking fish oils- again tethered to the back of the ship and freshly chopped horse mackerel for drawing them nearer to the ship. Chopping the horse mackerel is a relatively grim job, we have lost count of the number of eyeballs sliding across the deck. Amusingly we are using dog ball throw sticks to fling out the mackerel - it never ceases to amaze me the ‘field kit’ usefulness of the everyday item.
Bird-catching © Marguerite Tarzia
Catch of the day
Ewan Wakefield, our Principal Scientific Officer, has the task of concocting the various methods we can deploy to try to catch our target species: Northern fulmar, Great shearwater, Cory’s shearwater and Sooty shearwater. This has never been attempted from a ship of this size that we know of and is certainly never happened before on RRS Discovery. The crew are enjoying the spectacle. We have several nets and poles of various sizes and designs to try to catch our subjects and on our first position attempt Ewan caught a Great shearwater using a cast net with skill.
Buoyed with expectation, we have sampled two subsequent sites but alas, lower densities, swell size and tantalisingly close ‘misses’ mean we have still many more to try to catch. In the evenings, we stop to collect CTD data and deploy plankton nets, the bright lights of the ship can often confuse storm petrels who may land on the deck during this time. As such, we have caught three birds during these events, so thus far its scientists 1: ship 3 in terms of bird catching.
Fulmars at sea © Marguerite Tarzia
We entered a lull in wind and high seas yesterday, so Ewan and the Captain decided conditions were good enough to do a trial run of bird catching from a smaller boat launched from the ship. This could be a risky procedure, but in the hands of the skilled crew this first launch looks a promising method for multiple catches in higher densities of birds. The expedition continues…
Taking out the rescue boat to catch birds © Marguerite Tarzia
Stay tuned for an upcoming post by Paloma Carvalho who will be writing a blog entry on data loggers and moulting in shearwaters.
Follow the RSS Discovery's position on the National Oceanography Centre's 'Vessel Tracker'.