Iris dark brown; bill, legs and feet black. This species has the entire head, mantle, scapulars, back and upper rump and upper tail sooty brown-black. Nape, mantle and scapulars, back and upper rump with grey wash in good light. Longest scapulars thinly edged very pale grey. Upper tail coverts white (white feather shafts) forming a white rump band c. 15 mm wide in the centre and c. 20 mm wide at the sides. Lower 10 mm of upper tail coverts tipped black, same as upper tail. Bases of outer three tail feathers white, extending 33 mm from feather base on outmost tail feather. Chin and throat slightly paler than upper headparts. Breast, belly, upper flanks, central undertail coverts noticeably browner than upperparts. Lower flanks and bases of outer undertail coverts white, forming a contiguous white band with rump, so the white rump ‘wraps around’ the flanks, but not joining ventrally. Underside of tail feathers brown-black (very similar to underparts) with silvery sheen. Undertail coverts extending almost to tail tip centrally. Wing: Lesser coverts, carpal coverts, primary coverts, primaries and secondaries uniformly sooty brownblack. Noticeable light-drab diagonal wing bar extending from tertials (and inner secondary), across the greater and median coverts, to the outer lesser coverts, almost reaching the leading edge of the wing. The outer three greater coverts have outer lower edge concolorous with the primary coverts. Underwing, but it appeared wholly dark, similar in colour to underparts. On current knowledge, Monteiro’s Storm-petrel is known only from the Azores islands and appears to have diverged between 125 000 and 300 000 years ago from populations in the Pacific and between 70 000 and 350 000 years ago from other populations within the North Atlantic. Within the Azores, the species is known to breed only on two small (c. 12-ha) islets, some 5 km apart, lying off the inhabited island of Graciosa. The combined breeding population at these two sites has been estimated at 200 pairs. Further small colonies, possibly holding a few tens of pairs, are suspected on other islets lying off Graciosa, Flores and Corvo. The total breeding population is therefore estimated at between 250 and 300 pairs, but there is a clear need for more accurate and up-to-date information on population size and demography. The distribution of Monteiro’s Storm-petrel outside the breeding season is currently unknown, although the capture of two individuals on Praia Islet in late October and a further individual on Vila Islet in mid November suggests that it remains in the vicinity of the breeding grounds, rather than dispersing into the western Atlantic.
M. Bolton, A.L. Smith, E. Gomez-Diaz, V.L. Friesen, R. Medeiros, J. Bried, J.L. Roscales & R.W. Furness (2008) “Monteiro’s Storm Petrel Oceanodroma monteiroi: a new species from the Azores” Ibis 150 (4): 717?727