Altitudinal migration by birds: a review of the literature and a comprehensive list of species

Abstract

Altitudinal migration is the seasonal altitudinal movement of birds from breeding areas to non‐breeding or wintering areas at different elevations. Although this type of migration is widely reported, questions remain concerning the number of species that perform altitudinal migration, possible variation among different taxa and geographic locations in the extent of altitudinal migration, and the foraging guilds of altitudinal migrants. We conducted an extensive bibliographic survey and compiled a list of altitudinal migrant birds worldwide. We characterized species in terms of their foraging guilds because the spatial distribution of food resources along altitudinal gradients is often evoked as a driver of bird altitudinal migration. We identified 1238 species of altitudinal migrants, ~10% of the ~10,000 extant species of birds. We found a strong geographic bias in publications focusing on avian altitudinal migration toward the United States and Costa Rica, and a paucity of studies in megadiverse regions such as the Afrotropical and Indomalayan realms, and areas in the Neotropics other than Costa Rica. We also found that most species of altitudinal migrants were invertivores rather than frugivores or nectarivores. This general pattern held true for all zoogeographic realms except the Neotropics, where nectarivores and frugivores predominated among altitudinal migrants. The prevalence of invertivore birds among altitudinal migrants is not unexpected because this is the most common foraging guild among birds worldwide. Overall, we found no prevalence of any specific foraging guild among altitudinal migrants across zoogeographic regions. The results of studies to date suggest that altitudinal migration by birds may be driven by a number of factors, including access to increased food resources for breeding or molting, weather conditions, and mating and nesting opportunities. However, to better understand the mechanisms underlying altitudinal migration, broadening the geographic scope of studies is paramount, with additional study of altitudinal migration especially needed in the megadiverse tropical regions of sub‐Saharan Africa, Southeast Asia, and South America.

Survival is negatively related to basal metabolic rate in tropical Andean birds

“…Another feature common to tropical birds that could lead to their permanent emigration is altitudinal migration. Although our understanding of the birds that undertake seasonal altitudinal movements is far from complete, >500 species of altitudinal migrants are currently described from the Neotropics, of which the majority are also frugivores (Barçante, Vale, & Alves, ; Merkord, ). For example, our estimate of apparent survival for Chiroxiphia boliviana ( φ = 0.39, SE = 0.16), a frugivorous altitudinal migrant (Villegas, Newsome, & Blake, ), was between 28% and 85% lower than other sympatric manakin species.…”

Altitudinal migration: ecological drivers, knowledge gaps, and conservation implications

“…We added additional sources including theses/dissertations or book chapters to our review when referenced by literature returned by our initial searches. We also included previous reviews of altitudinal migration, including two of birds (Barçante, Vale & Alves, ; Boyle, ), and one of bats (McGuire & Boyle, ).…”

“…However, recent advances in animal‐movement‐tracking technologies (e.g. GPS loggers and lightweight radio tags) now make tracking animals of smaller sizes attainable (Bridge et al ., ; Barçante et al ., ). Although telemetry may be the best option for studying individual movement behaviour, capture–mark–recapture methods are another viable option.…”

A meta-analysis of global avian survival across species and latitude

“…One of the drawbacks of 455 capture-mark-recapture data is that the reported metric, apparent survival, is a product of true 456 survival and site fidelity and as such will always be biased low, whereas estimates of survival 457 from dead recovery models are often interpreted as true survival (Sandercock 2006). Biases in 458 survival estimates may therefore be strong for birds from tropical regions, which consisted 459 exclusively of live-recapture data, and where behaviors such as altitudinal migration are more common than in temperate regions (Barçante et al 2017) and can lead to permanent emigration 461 from study plots. Another issue affecting the comparison of survival studies is the study duration.…”