New Caledonia & Vanuatu
There is one field guide for the region: Birds of the Solomons, Vanuatu & New Caledonia (ISBN 978-0-7136-4690-0) by Chris Doughty, Nicholas Day, and Andrew Plant.
The guide is small, lightweight, and relatively modern. It illustrates and describes all regularly occurring species in the region, including an astonishing 60 species never before illustrated. There are range maps, but they are sometimes difficult to read (because the islands are small), and birders familiar with Vanuatu say that the maps contain several errors. Some illustrations are quite good; others are less than inspired. But it’s hard to complain when the publication is so groundbreaking.
Unfortunately, the guide is becoming hard to find, especially if price is a concern for you. Try NHBS and compare prices at the major online booksellers.
Heinrich L. Bregulla’s Birds of Vanuatu is an older reference work (not a field guide) that may still provide helpful range/distribution information and species accounts for birders who plan to spend time in Vanuatu.