It is always difficult to locate a singing Spotted Dove (Streptopelia chinensis) in my garden. The song may sound loud and clear, yet I have always been unable to locate the bird in the tree, even when the tree is sparsely leaved or shortly trimmed. Then one day I did manage to locate the singing dove in a closely trimmed Macarange heynei tree.
The deutting was loud and distinct. One sang loudly while its partner replied with a softer song. Close observations showed that the singing was made with the bill closed (above left). Only the throat vibrated a little.
On 5th October 2010, I was under the same tree and easily located the singing bird. It sang differently this time. Then it flew to my neighbour’s house and continued singing. Initially the bill gaped slightly (above right), just before the song was heard and was completely clamped when the song came through.
Discussions on vocalising barbets and bill behaviour can be found HERE: 1, 2 and 3.
You have nice experience of the behavior of the dove.