Nycticorax olsoni   (N. P. Ashmole, K. E. L. Simmons & W. R. P. Bourne)

Ascension Island Night-Heron
(Nycticorax olsoni)

syn. -


British Overseas Territory of Saint Helena, Ascension and Tristan da Cunha: Ascension Island

local name: -

size: 50 - 60 cm (length)

extinction date: sometimes after 1557

This species of Night-Heron was described in the year 2003 on the basis of subfossil bones, which were foun in guano deposits. In live this species was somewhat smaller than the Night-Heron (Nycticorax nycticorax (L.)) and it was most probably a weak flyer but not fully flightless.

The Ascension Island Night-Heron may have stayed near the coast, where it searched the giant sea bird colonies existing on the island at that time for unattended fledgelings, resp. fished for crustaceans at the shore.

The circumstances for its extinction are not known, but introduced rats may well have played a role as they did in so many other cases of extinctions of birds on islands.


In chapter 21 (D'une isle nommée l'Ascention.) of his book 'Les singularitez de la France antarctique, autrement nommée Amérique, et de plusieurs terres et isles découvertes de nostre tems.' from the year 1557 André Thevet describes a bird from Ascension Island which indeed could well be the Ascension Island Night-Heron.:

Dauantage en ceste isle s'en trouue une espece de grands, que i'ay ouy nommer Aponars. Ils ont petites ailes, pourquoy ne peuuent voler. Ils sont grands et gros comme noz herons, le ventre blanc, et le dos noir, comme charbon, le bec semblable à celuy d'un cormoran, ou autre corbeau. Quand on les tue ils criênt ainsi que porceaux.


Furthermore in this Ilande there is a certayne kinde of greate birdes that I have heard called Aponars, they have little wings, and therefore they cannot flye. They are great and hye lyke hearnshawes, the belly white, and the backe blacke as cole, the byll lyke to a cormorant, or a different crow. When they are killed they crye lyke hogs.


- A. Thevet: The new found worlde, or Antarctike. London: Henrie Bynneman for Thomas Hacket, 1568
- W. R. P. Bourne; N. P. Ashmole; K. E. L. Simmons: A new subfossil night heron and a new genus for the extinct rail from Ascension Island, central tropical Atlantic Ocean. Ardea 91: 45-51. 2003