Day 24: Spectacular seabirds
By Jamie Menzies
As we near the end of our four-week voyage, we have recorded over 14,000 seabirds across 27 different species. The most common including Sooty Terns and Brown Noddies, as well as plenty of Boobies, Shearwaters and Tropic Birds. We sometimes see these birds in groups of up to a thousand in spectacular tuna bait balls; these feeding frenzies happen when hunting tuna drive smaller fish up to the surface which makes perfect pray for hungry seabirds.
Three scientists have spent their days in the observation deck, one of the highest points of the ship, armed with binoculars and cameras to spot these seabirds in action. The scientific aim is to understand the distribution of these seabirds across space and time.
A benefit to spotting these birds in their natural habitat is getting to see some spectacular foraging behaviour. Foraging is a term that biologists use to describe when an animal is searching for food, and the seabirds we’ve seen have a particular tendency towards flying fish!
The boobies are often seen plunge diving – flying at about 20 metres high, they pull in their wings and shoot down at high speed to unsuspecting fish. This instinct or trait gives them a good chance of securing a meal.
Another foraging behaviour that we see is called kleptoparatism. Parasitism is when an animal benefits at the cost of another, and the prefix klepto– refers to stealing. The scientists have observed Frigate Birds harassing other birds by flying at them and pecking towards them until they drop their fish – allowing the frigates to swoop in and catch the dropped prey.
As well as feeding, we’ve also had a chance to spot birds roosting, which means resting for the night. Seabirds can roost on the sea surface, on islands, vegetation patches and, luckily for the bird scientists, on the mast of RV Investigator.