Guest blog by Dr Steffen Oppel, Senior Conservation Scientist, RSPB Centre for Conservation Science. You can read Part 1 of the science expedition to Henderson Island here.
On 22 May 2015, the RSPB expedition team arrived on Henderson (Pitcairn Group, UK Overseas Territory) to better understand the ecology of this remote and rarely visited island.
Monitoring Henderson rail and other landbirds
The team has been on the island for about 3 weeks now, and has completed the first round of bird counts and rat trapping.
The team are monitoring the four endemic landbird species (Henderson fruit-dove, Henderson lorikeet, Henderson rail and Henderson reed-warbler) on Henderson to assess whether populations have changed in the four years since the failed rat eradication attempt.
The landbird counts are very encouraging so far, with far more of the endemic Henderson rail being seen and heard across the island than in 2013. The species declined considerably following the bait drop in 2011, but current data suggest that the population has almost fully recovered.
Photo: Henderson rail by Richard Cuthbert
Ten rails have been caught and are being fed in captivity to examine whether they are equally likely to swallow blue rat bait as they swallowed green rat bait, which was used during the 2011 eradication attempt.
The Murphy's Petrels have started breeding, and the team has deployed 4 GPS loggers on incubating birds to track their movements, but so far none of these birds has left their nests.
Photo: Murphy's petrels by Richard Cuthbert
Rat densities and movement on the island
Henderson’s unique biodiversity is currently under threat due to the presence of introduced Pacific rats. One of the key goals of the 2015 expedition is to get a better understanding of the density and movement ranges of rats on the island. Unfortunately, the rat population has also recovered.
The team has captured >150 individual rats so far, and has recorded some long movements of rats across the island. The longest movement of 330 meters in a single day from one trap to another vastly exceeds previous information obtained by radio-tracking in 2013. Some rats near the camp site have apparently survived since 2013, as the team found rats with ear tags from previous expeditions.
Living on one of the most remote islands on the planet
The last week saw some intense rainfall which flooded the camp and had the whole team digging up drainage ditches, but overall we were all happy to have our water tanks full to the brim and even had enough fresh water to take a cleansing shower!
Over the next few months the team will collect more data on vegetation, landbirds, rats, and seabirds, before being relieved by another crew at the end of August.
The Henderson expedition is funded by The Darwin Initiative and David & Lucile Packard Foundation.
Find out more about our Henderson Island Restoration Programme
Great work by the RSPB and Birdlife International
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