Data from: Migratory, molting, and overwintering strategies of sagebrush-associated songbirds are diverse and flexible

Abstract

The nonbreeding period constitutes most of the annual cycle for many migratory animals, and nonbreeding conditions can affect current and future fitness outcomes. The flexibility and diversity of nonbreeding movement strategies for breeding populations can therefore have consequences for population dynamics, particularly with rapid environmental change. The diversity of movement strategies across contexts and the mechanisms underlying such diversity in breeding populations, however, remains unclear. We investigated the diversity and flexibility of movement strategies across multiple levels of biological organization (species, populations, and individuals) and nonbreeding stages (prebasic molt and overwintering) for a breeding bird community of the North American sagebrush biome. Movement strategies varied extensively both within and among focal species: Brewer’s sparrow (Spizella breweri; n = 22), sagebrush sparrow (Artemisiospiza nevadensis; n = 13), and sage thrasher (Oreoscoptus montanus; n = 7); all obligate migrants. S. breweri demonstrated a mix of movement strategies to molting sites, including molt migration to diverse sites and breeding-molt overlap. During the overwintering period, S. breweri demonstrated range residency, whereas A. nevadensis and O. montanus used both nomadic and resident strategies. Individuals tracked across multiple years (n = 7) revealed support for the migratory flexibility hypothesis – that migratory spread of the population was associated with the behavioral flexibility of individual adults. Such flexibility may buffer populations against increasingly variable conditions associated with anthropogenic change, yet flexibility also highlights the need for broader-scale, rather than site-specific, conservation strategies focused on the full annual cycle. In summary, we document high intraindividual, intrapopulation, and interspecific variation in movement strategies across multiple periods of the annual cycle, with implications for full annual cycle ecology and conservation strategies.