Long-distance migration is a feature of the terrestrial avifaunas of most continents, notably those of Eurasia and North America. There, lengthening spring days and warmer temperatures prompt millions of birds to move towards higher latitudes (see Alerstam 1990; Berthold et al. 2003; Greenberg and Marra 2005). Among the most spectacular of these migrations are the millions of waterfowl and shorebirds migrating between high-latitude breeding grounds across the Holartic and non-breeding grounds in the southern hemisphere, and the annual movements of songbirds, raptors and others between the forests of the Neotropics and breeding grounds in North America. Yet among terrestrial species (except shorebirds) only seven migrate to Australia from a pool of 234 Palearctic species that migrate to South East Asia (Dingle 2004, 2008). All seven are non-breeding migrants to Australia, of which only three, oriental cuckoo Cuculus optatus, white-throated needletail Hirundapus caudacutus and fork-tailed swift Apus pacificus are common visitors (Dingle 2004). It is this dearth of migration between Australia and Eurasia that is our primary focus here.

For a wide range of Australo-Papuan landbird species there is no broad environmental condition likely to warrant an ‘out of Australia’ response to Asia or further afield. The resources they need can be found elsewhere within Australo-Papua. In the south, swift parrots migrate hundreds to thousands of kilometres from Tasmania to the mainland seeking widely dispersed nectar and psyllid resources in the Austral winter (Saunders and Heinsohn 2008). As winter develops, southern populations of rainbow bee-eater and others migrate north and some depart the continent to New Guinea and islands beyond. In the north, pied imperial pigeon, metallic starling, buff-breasted paradise kingfisher and others migrate annually between the tropical forests of northern Australia and New Guinea to exploit seasonally available resources (e.g. Legge et al. 2004). A key feature of migration within Australia is the preponderance of partial migration, the phenomenon of some populations or individuals and not others of a species undertaking migration. This arises through variable responses of individuals and populations to irregular weather patterns and subsequent uncertainties of the whereabouts and availability of food resources (Chan 2001). For Palearctic migrants passing through the archipelagos of South East Asia, this uncertainty likely precludes extending migration to the Australian continent, except to habitats that are reliably productive in the Austral summer, such as the coastal habitats used by migratory shorebirds.