Dispersal, Mimicry, and Geographic Variations in Northern Melanesian Birds

Abstract

I present new information about 34 of the 195 resident land and freshwater bird species of Northern Melanesia, an area characterized by a rich avifauna, high endemism, and great geographic variation in morphology. There are many examples of geographic variation in voice, behavior, habitat preference, altitudinal range, vertical stratum, abundance, and nest. Possible vocal convergence or mimicry between sympatric populations of different species is described between the goshawk Accipiter albogularis and the kingfisher Halcyon chloris, between the cuckoo-shrike Coracina [tenuirostris] and other species in its mixed-species foraging flocks, between the white-eyes Zosterops murphyi and Z. rendovae kulambangrae, and between the starlings Aplonis grandis and Mino dumontii. Hybridization is reported between the Bismarck and New Guinea races of the cuckoo Eudynamys scolopacea on Long Island (described as a new subspecies), between the whistlers Pachycephala pectoralis and P. melanura, and between the honey-eaters Myzomela tristrami and M. cardinalis. Cyclones bring Australian species, some of which occasionally remain to breed. Over-water dispersal ability varies greatly, from species that can be seen flying over water any day to species that rarely or never cross water. For instance, a channel 12 km long and only 0.15-1 km wide divides Florida Island into two halves, one of which possesses and the other of which lacks a resident population of the coucal Centropus milo.

Northern Melanesia comprises the hundreds of islands of the Bismarck and Solomon Archipelagoes east of New Guinea. Its rich avifauna, their intensively studied distributions and taxonomy, the marked geographic variation in morphology of conspecific populations among different islands, and the existence of bird species representing many different stages in the speciation process have all combined to make Northern Melanesian birds ideal material for studying speciation (Mayr 1942 and many papers). However, little has been reported about geographic variation in ecology, behavior, and vocalizations. The Northern Melanesian avifauna includes many little-known endemic populations (five endemic genera, 30 endemic full species or superspecies, 102 endemic allospecies, and 380 endemic subspecies). Rampant ongoing deforestation of Northern Melanesia makes it urgent to study this treasure trove of diversity before much of it disappears.

Between 1969 and 1976 I made four expeditions to Northern Melanesia: 27 June-24 July 1969, West New Britain; 23 June-1 September 1972, Umboi and Long and neighboring islands, and Bougainville; 18 August-31 October 1974 and 5 September-15 October 1976, almost all ornithologically significant Solomon islands (except Buka, Ysabel, Malaita, Ulawa, Ramos, Gower, and the remote outliers), plus 94 small islets in and near Wana Wana Lagoon of the New Georgia group. Previous publications have described the avifaunas of Rennell and Bellona (Diamond 1984), vocalizations of the white-eye superspecies Zosterops [griseotinctus] (Diamond 1998), character displacement in myzomelid honey-eaters (Diamond et al. 1989), community assembly (Diamond 1975a), selected species of Bougainville (Diamond 1975b) and West New Britain (Diamond 1971, 1972) and Umboi and nearby islands (Diamond 1974, 1976), species/area/distance relations (Diamond and Mayr 1976, Diamond et al. 1976, Gilpin and Diamond 1976, 1981), the montane avifauna (Mayr and Diamond 1976), and two new taxa (Diamond 1989a, 1991).

In this paper I report significant field observations and distributional records—especially ones involving endemic populations and/or concerning geographic variation, vocalizations, overwater dispersal, and hybridization. I also mention two records based on unreported specimens that I found in museums.

Taxonomy and distributions are based on a comprehensive, just-published account of the Northern Melanesian avifauna by Mayr and Diamond (2001), hence information in that book is not repeated in this paper. To facilitate finding such information, I cite each resident species by its number used in Appendix 1 of that book. To facilitate use of the taxonomic literature on Northern Melanesian birds, most of which predates 1960, the island names and spellings used here and in that book are those then in use, differing in nine cases from modern names and spellings (the older Florida, Ganonga, Gatukai, Gizo, Gower, Kulambangra, New Hanover, San Cristobal, and Tetipari rather than the current Nggela, Ranongga, Nggatokae, Ghizo, Ndai, Kolombangara, Lavongai, Makira, and Tetepare, respectively). I frequently...