The Pacific as the world’s greatest theater of bird migration: Extreme flights spark questions about physiological capabilities, behavior, and the evolution of migratory pathways

Abstract

The Pacific Basin, by virtue of its vastness and its complex aeroscape, provides unique opportunities to address questions about the behavioral and physiological capabilities and mechanisms through which birds can complete spectacular flights. No longer is the Pacific seen just as a formidable barrier between terrestrial habitats in the north and the south, but rather as a gateway for specialized species, such as shorebirds, to make a living on hemispherically distributed seasonal resources. This recent change in perspective is dramatic, and the research that underpins it has presented new opportunities to learn about phenomena that often challenge a sense of normal. Ancient Polynesians were aware of the seasonal passage of shorebirds and other landbirds over the Pacific Ocean, incorporating these observations into their navigational “tool kit” as they explored and colonized the Pacific. Some ten centuries later, systematic visual observations and tracking technology have revealed much about movement of these shorebirds, especially the enormity of their individual nonstop flights. This invites a broad suite of questions, often requiring comparative studies with bird migration across other ocean basins, or across continents. For example, how do birds manage many days of nonstop exercise apparently without sleep? What mechanisms explain birds acting as if they possess a Global Positioning System? How do such extreme migrations evolve? Through advances in both theory and tracking technology, biologists are poised to greatly expand the horizons of movement ecology as we know it. In this integrative review, we present a series of intriguing questions about trans-Pacific migrant shorebirds and summarize recent advances in knowledge about migratory behavior operating at temporal scales ranging from immediate decisions during a single flight, to adaptive learning throughout a lifetime, to evolutionary development of migratory pathways. Recent advances in this realm should stimulate future research across the globe and across a broad array of disciplines.

Beyond Site-Specific Criteria: Conservation of Migratory Birds and Their Habitats from a Network Perspective

“…However, the feasibility of this approach should be evaluated with scientific understanding of spatiotemporal bird distributions. For example, it may not be suitable for species that skip stopovers, using a "jump migration" strategy [24]. In addition, we suggest dynamically measuring the networks because loss or degradation of certain sites in the network could affect the distribution of keystone sites.…”

“…It may also be used for identifying a network of sites of importance for "resident" bird species undertaking long-distance dispersal or range expansion/contraction due to environmental changes [4]. However, this approach is less useful for some terrestrial birds or waders that do not regularly use stopover sites during migration [24]. Although many of the international conservation frameworks are specially formulated for waterbirds (Table 1) and a large proportion of the reviewed studies are for waterbirds, this approach also fits other taxa that use similar migration strategies.…”

Variation in movement strategies: Capital versus income migration

“…plumage moult, reproduction) being accommodated within the migratory cycle. It should, however, be noted that possible exceptions to these expectations have been outlined (Conklin et al, 2017 ) and it has been posited that long‐distance (avian) migrants may be capable of torpor (Carpenter & Hixon, 1988 ; Hiebert, 1993 ), facultative hypothermia (Carere et al, 2010 ; Wojciechowski & Pinshow, 2009 ) or other, unidentified improvements to energetic efficiency (Piersma et al, 2022 ).…”

“…Inevitably, given the demands of large‐scale movement, energetics is a key driver for the evolution of migration (Avgar et al, 2014 ; Hein et al, 2012 ; Piersma et al, 2022 ; Roff, 1991 ). Indeed, based on their fuelling strategies, Theunis Piersma organised migrating birds into a sequential – rather than strictly categorical – system.…”

Do 50‐year‐old Ramsar criteria still do the best possible job? A plea for broadened scientific underpinning of the global protection of wetlands and migratory waterbirds

“…As a fifth concern, waterbirds are faced with many aspects of global change, either climate change or wetland shrinking due to water deprivation in their many different forms (Hu et al., 2017). For example, shorebirds making long‐distance nonstop flights have to cope with serious physiological demands during migration (Piersma et al., 2022). The current destabilization of global circulation patterns (i.e., position of climate cells) lead to more unusual environmental conditions, for example, increases in the frequency of events such as El Niño/La Niña Southern Oscillation (Timmermann et al., 2018).…”