The Henderson Island Experience

18 Dec 2015

Sarah Havery works as a Projects Assistant for the RSPB UK Overseas Territories and International Species Recovery teams and had the exciting opportunity to join the Henderson Expedition team in 2015. This is her Henderson story:

Imagine white sand beach. Clear blue seas. Coral reefs. Coconut palms. Humpback whales. Green turtles. All you can hear is the sea roaring over the reef and seabirds calling as they whirl overhead. Welcome to Henderson Island, a British World Heritage Site and one of the remotest islands on this planet.

View across north beach, Henderson Island

I was lucky enough to join the Phase 2 expedition team from August to November 2015 to help with the invaluable scientific research. The first big adventure though was actually getting there in the first place! Directions to Henderson: First, catch a flight from London to Los Angeles, then another flight from L.A. to Tahiti, then take a further four hour flight across French Polynesia (which surprisingly spans an area larger than the whole of Europe) to the island of Mangareva. Then, catch a boat for two days to Pitcairn Island, meet the descendants of the mutineers of the Bounty and pick up any last minute supplies, before continuing overnight to arrive at Henderson Island.

Sunrise over Henderson Island from the Claymore II

I will never forget that first sunrise over Henderson viewed from the boat. We had masked boobies and Greater frigatebirds soaring overhead, with the sun rising to reveal a forest-covered cliff spanning the island’s coast and the phase 1 team waving from the beach. After two days of hand-over, phase 1 left to make the return journey home and phase 2 settled into Henderson life. Henderson Island is so remote that there is no phone signal, no radio stations and certainly no internet! Fortunately we were armed with a satellite phone so we could get regular updates to RSPB HQ.

We quickly settled into our new lifestyle and cracked on with the research. The work programme covered a whole range of studies to improve our understanding of the island, ranging from a study to determine the density of the Pacific rats, to seabird monitoring, to entomological studies.

Sarah working on the Capture-Mark-Recapture study

To obtain a rat density estimate, a capture-mark-recapture study was used by marking individual rats with ear tags. We were also studying food preference of the introduced rats to gain an insight into the impacts they have on native flora and fauna. We observed flushes of different food types available in the forest, such as certain tree species going to fruit (notably the endemic tree Myrsine hosakae), which was followed by a sudden abundance of caterpillars. We noticed that during these fruiting and invertebrate emergences it sounded as though it was raining in the forest... in reality, caused by the rats gorging themselves on Myrsine fruit and dropping the seed pods, and then also due to the sheer amount of caterpillar droppings falling from the sky!

A rat eating the fruit of the endemic tree Myrsine hosakae on Henderson Island

During the expedition the team monitored the nests of masked boobies, Henderson petrels and Murphy’s petrels, to provide an indication of breeding success and predation pressure from rats, as well as morphometric information for the petrel species. We also managed to deploy a GPS logger onto an adult Henderson petrel for the first time, so amazingly we have the first indication of where this species goes to feed. It is incredible how much we still don’t know about the wildlife of Henderson Island, especially considering the birds are the most studied group of the flora and fauna.

Greg and Neil taking measurements of the chick from HEPE26 (which stands for Henderson Petrel nest number 26)

HEPE28 nest was found with an egg at the start of the Phase 2 trip and hatched over a month later. Henderson petrels have a relatively long incubation period of 55 days on average.

Andy Skinner was the team’s entomologist, who managed to collect lots of invertebrate samples (including some species that are newly recorded for Henderson Island) and undertook the first standardised surveys of the invertebrate diversity present. We had the exciting privilege of observing some of the island’s endemic invertebrates such as the endemic hawk moth and shieldbug.

Andy the entomologist in action! Andy spent the entire three months searching for the elusive endemic shieldbug... which he finally found during the final week of the trip!

The endemic shieldbug of Henderson Island – this beautiful critter is found nowhere else in the world.

The marine life observed from Henderson was just incredible, and some of the most awesome wildlife encounters I have ever experienced. I had the privilege of watching humpback whales coming to the surface only 50 metres offshore (due to the seafloor dropping off very quickly beyond the reef), and occasionally whilst working in the forest on the plateau you would suddenly hear a loud BOOM!... the distinctive sound of an adult humpback breaching! There were at least three adult females with calves observed swimming around the island. One of my most memorable evenings from the whole trip was when the team was eating dinner by the beach, whilst a female humpback and her calf were cruising along the shoreline. They swam parallel to the shoreline, until they were as close to us as they possibly could get, when at that point the young calf breached out of the water – spinning as it went! The adult then began tail slapping, as if in encouragement, and this display continued for about 10 minutes before they’d had enough, and disappeared into the abyss.

The humpbacks left at the end of September, migrating to the cold, productive southern waters. However, then the green turtles started making early season landings on the beach. By the time we left, we observed three turtle tracks on the beaches, and with signs of digging present it was clear the breeding season was due to start. With at least five individuals observed at one time, it was truly magical to be on a beach outnumbered by turtles. This little glimpse into the diverse marine life of Pitcairn’s pristine waters really highlighted the importance of the newly designated Marine Protected Area (MPA) to me, and why we need to ensure these waters are protected for the future.

Sarah and an adult green turtle on east beach

The Henderson Expedition offered a fantastic opportunity to work as part of a team with experiences from across the world. Sue & Pawl (more commonly known as Pirate Pawl!) from Pitcairn Island spent the whole six months of the expedition on Henderson. Their passion for the continued conservation work on Henderson was truly inspiring, having been involved with many previous research projects and the previous rat eradication attempt in 2011.

Sue & Pawl collecting rat data in the field

The Henderson 2015 expedition has given me a small insight into the amazing world of Henderson Island, and has shown it is truly a place worth protecting. With the results of this expedition and with future research work, we can really start to build a picture of what needs to be achieved to ensure the long-term conservation of this beautiful remote island and its’ incredible wildlife.