ABSTRACT
149Plovers of the subfamily Charadriinae demonstrate nearly every conceivable annual movement pattern found among birds, including long- and short-distance latitudinal migration, altitudinal migration, irruption, nomadism, and sedentary habits. Within species, and even within some populations, inter-individual differences may range from completely sedentary birds to some of the longest avian migrations yet recorded. This extreme variation makes plovers an interesting group in which to explore the ecological and evolutionary drivers and consequences of movement patterns. In this chapter, I review patterns of movement according to geography, molt, wing morphology, various aspects of annual-cycle strategies, and the known evolutionary history of the group. Of 40 plover species, 26 (65%) are migratory to some degree, and these are found on nearly all global migratory flyways, with the greatest number on the East Asian-Australasian Flyway. The species diversity and the proportion of nonmigratory plovers are highest in the Eastern and Southern Hemispheres. Migration distance increases with breeding latitude; the longest migrations are performed by arctic-breeding plovers, and no Southern Hemisphere breeders migrate further north than the tropics. In general, individual migration strategies are poorly described, but include both short-hop migrations and nonstop flights of at least 5,300 km and perhaps more than 7,000 km in some species. Wing shape varies with migration distance, suggesting that movement patterns and morphology coevolve to some degree, and that some species may be predisposed to greater flexibility in movements. Repeated loss of migration appears to be a significant form of diversification in plovers; recent phylogenetic evidence supports historical radiation from a northern migratory ancestor, and current distributions of sedentary species, particularly on islands, suggest a pattern of isolation from mainland migratory species. Although some species show evidence of evolutionary constraints on migration routes, the present-day diversity of movement patterns implies great flexibility to respond to changing circumstances at multiple time scales. However, the general lack of specific information regarding routes and habitats used during migration is a major obstacle to developing effective global conservation strategies for migratory plovers.
