Mysterious Cave Dwellers

Seabirds living in caves? Surely not!

Prions nest all over Gough, from burrows to rocky crevices, and the main study colony just so happens to be in a cave. These delightful birds are one of the most numerous on Gough and there may be some two million pairs on the island!

Outside the cave.....(David Kinchin-Smith)

......and inside (David Kinchin-Smith)

Prions are a small, blue-grey petrel with a fairly remarkable bill. Known as ‘Whalebirds’, a combination of filtering lamellae and an expandable gular pouch in their broad bills means that these birds are able to filter feed like, as Ryan et al. (2007) aptly puts it, “a tiny baleen whale”.

Until very recently, Broad-billed Prions were thought to be the only breeding prion species on Gough. However, research by Ryan et al. (2014) over the course of a few years revealed evidence for two separate prion species on Gough. The prions breeding in the main study colony of Prion Cave were shown to be significantly smaller billed and bred some three months later than those elsewhere on the island. The Prion Cave birds are more similar in size and their timing of breeding to Macgillivray’s prions, a species found on Amsterdam and St Paul islands in the temperate Indian Ocean. There is still so much waiting to be discovered on the island, and our prions are just one of Gough’s many mysteries.

Magnificent Macgillivray's! (David Kinchin-Smith)

The closely related Broad-billed Prion (David Kinchin-Smith)

Each year, around 50 prion nests are monitored in the Cave. The first eggs were discovered in late November and we will hopefully be welcoming our first chicks over the next couple of weeks.

Pair-bonding at the start of the season (David Kinchin-Smith)

Followed by preparing the nest (David Kinchin-Smith)

And now incubating an egg! (David Kinchin-Smith)

David

Reference.

Ryan, P. G. et al. (2014) The occurrence of two bill morphs of prions Pachyptila vittata
on Gough Island. Polar Biol (2014) 37:727–735

Ryan, P. et al. (2007) Field Guide to the Animals and Plants of Tristan da Cunha and Gough Island