Silver-tipped thought at the time because commonly present, but the very few recordings do not have this intro note; later in the morning Khaleb Yordan identified this species in the recording from 0614 hours with the same vocalization, with a very short introductory note; very few recordings of this species on XC and Macaulay, and they don't have the introductory note, though on other species of Columbid that is often lost; main note lasts 0.07 seconds, which is given in the Eaton et al. field guide;

bird-seen:no

playback-used:no

Tentative ID on the basis no other Ducula species recorded at this location appears to make a song like this. It sounds quite similar to Spectacled Imperial Pigeon (Ducula perspicillata) which is endemic to the Maluku islands, which I am guessing Grey-headed Imperial Pigeon is closely related to. Another species found here with calls that are not well-documented is Silver-tipped Imperial Pigeon (Ducula luctuosa), but I would expect those sounds to be more similar to other black & white Ducula species and quite different to this.

bird-seen:no

not seen actually vocalizing, but multiples seen at this spot; a short intro note to the long whooo, also one series of notes presumed to also be from this species; interval altered at 0:34, a confusing recording with the lower pitched Imperial-Pigeon and higher (slightly) pitched Emerald Dove both have an introductory note; very few recordings of this species on XC and Macaulay, and they don't have the introductory note, though on other species of Columbid that is often lost; the series of 'whoo' notes after 0:22 is like a couple of the recordings of Silver-tipped; the long note of these songs is about 0.07 seconds, which the Eaton et al. field guide gives as note length for this species;