Physiomorphic transformation in extreme endurance migrants:Revisiting the case of Bar-tailed Godwits preparing for trans-Pacific flights

In a 1998 paper entitled “Guts don’t fly: small digestive organs in obese bar-tailed godwits,” Piersma and Gill (1998) showed that the digestive organs were tiny and the fat loads huge in individuals suspected of embarking on a non-stop flight from Alaska to New Zealand. It was suggested that prior to migratory departure, these godwits would shrink the digestive organs used during fuel deposition and boost the size and capacity of exercise organs to optimize flight performance. Here we document the verity of the proposed physiomorphic changes by comparing organ sizes and body composition of bar-tailed godwits Limosa lapponica baueri collected in modesty midway during their fueling period (mid-September; fueling, n = 7) with the previously published data for godwits that had just departed on their trans-Pacific flight (October 19; flying, n = 9). Mean total body masses for the two groups were nearly identical, but nearly half of the body mass of fueling godwits consisted of water, while fat constituted over half of total body mass of flying godwits. The two groups also differed in their fat-free mass components. The heart and flight muscles were heavier in fueling godwits, but these body components constituted a relatively greater fraction of the fat-free mass in flying godwits. In contrast, organs related to digestion and homeostasis were heavier in fueling godwits, and most of these organ groups were also relatively larger in fueling godwits compared to flying godwits. These results reflect the functional importance of organ and muscle groups related to energy acquisition in fueling godwits and the consequences of flight-related exertion in flying godwits. The extreme physiomorphic changes apparently occurred over a short time window (≤1 month). We conclude that the inferences made on the basis of the 1998 paper were correct. The cues and stimuli which moderate these changes remain to be studied

Coping with the Cold: An Ecological Context for the Abundance and Distribution of Rock Sandpipers during Winter in Upper Cook Inlet, Alaska

Shorebirds are conspicuous and abundant at high northern latitudes during spring and summer, but as seasonal conditions deteriorate, few remain during winter. To the best of our knowledge, Cook Inlet, Alaska (60.6˚ N, 151.6˚ W), is the world’s coldest site that regularly supports wintering populations of shorebirds, and it is also the most northerly nonbreeding location for shorebirds in the Pacific Basin. During the winters of 1997–2012, we conducted aerial surveys of upper Cook Inlet to document the spatial and temporal distribution and number of Rock Sandpipers (Calidris ptilocnemis) using the inlet. The average survey total was 8191 ± 6143 SD birds, and the average of each winter season’s highest single-day count was 13 603 ± 4948 SD birds. We detected only Rock Sandpipers during our surveys, essentially all of which were individuals of the nominate subspecies (C. p. ptilocnemis). Survey totals in some winters closely matched the population estimate for this subspecies, demonstrating the region’s importance as a nonbreeding resource to the subspecies. Birds were most often found at only a handful of sites in upper Cook Inlet, but shifted their distribution to more southerly locations in the inlet during periods of extreme cold. Two environmental factors allow Rock Sandpipers to inhabit Cook Inlet during winter: 1) an abundant bivalve (Macoma balthica) food source and 2) current and tidal dynamics that keep foraging substrates accessible during all but extreme periods of cold and ice accretion. C. p. ptilocnemis is a subspecies of high conservation concern for which annual winter surveys may serve as a relatively inexpensive population-monitoring tool that will also provide insight into adaptations that allow these birds to exploit high-latitude environments in winter.Le printemps et l’été, les oiseaux de rivage abondent et sont bien en vue dans les latitudes de l’extrême nord, mais au fur et à mesure que les conditions saisonnières se détériorent, peu d’entre eux hivernent dans ces régions. Au meilleur de nos connaissances, l’anse Cook, en Alaska (60,6˚ N, 151,6˚ O), est l’endroit le plus froid du monde où l’on trouve régulièrement des populations d’oiseaux de rivage l’hiver. Il s’agit aussi de l’emplacement le plus nordique du bassin du Pacifique à ne pas être consacré à la reproduction des oiseaux de rivage. Au cours des hivers allant de 1997 à 2012, nous avons réalisé des levés aériens de la partie supérieure de l’anse Cook afin d’être en mesure de répertorier la répartition spatiale, la répartition temporelle et le nombre de bécasseaux des Aléoutiennes (Calidris ptilocnemis) dans l’anse. Le total moyen des levés a permis de repérer8 191 ± 6 143 (DS) oiseaux, tandis que la moyenne du dénombrement le plus élevé au cours d’une seule journée d’hiver était de 13 603 ± 4 948 (DS) oiseaux. Dans le cadre de nos levés, nous n’avons détecté que des bécasseaux des Aléoutiennes, dont tous étaient essentiellement des individus de la sous-espèce désignée (C. p. ptilocnemis). Au cours de certains hivers, les totaux des levés se rapprochaient beaucoup des estimations de population de cette sous-espèce, ce qui laisse entrevoir l’importance de cette région en tant que ressource de non-reproduction pour cette sous-espèce. La plupart du temps, ces oiseaux ne se retrouvaient qu’à quelques endroits de la partie supérieure de l’anse Cook, bien qu’ils se répartissaient plus au sud de l’anse pendant les périodes de froid extrême. Deux facteurs environnementaux permettent aux bécasseaux des Aléoutiennes d’évoluer dans l’anse Cook l’hiver : 1) une source abondante de nourriture acéphale (Macoma balthica) et 2) une dynamique de courants et de marées qui a constamment pour effet d’alimenter les oiseaux en substrat pendant toutes les périodes, sauf celles de froid extrême et d’accrétion de glace. C. p. ptilocnemis est une sous-espèce dont la conservation présente de grandes inquiétudes et pour laquelle les levés hivernaux annuels peuvent constituer un outil de surveillance de population relativement abordable qui permettra également d’en savoir plus sur les adaptations qui permettent à ces oiseaux d’exploiter les milieux de haute latitude l’hiver

APPARENT SURVIVAL OF BREEDING WESTERN SANDPIPERS ON THE YUKON-KUSKOKWIM RIVER DELTA, ALASKA

We used 8 years of live recapture data (1998–2005) to estimate apparent annual survival for male (n = 237) and female (n = 296) Western Sandpipers (Calidris mauri) breeding on a 36-ha plot on the Yukon-Kuskokwim River Delta, western Alaska. Apparent annual survival (Φ) is the product of true survival and site fidelity, and estimates of Φ were corrected for the probability of encounter. Overall return rates (individual returned to the study site in a subsequent season) were lower for females (40%) than males (65%), as was Φ (± SE, females = 0.65 ± 0.05, males = 0.78 ± 0.03), and encounter rate (females = 0.51 ± 0.07, males = 0.74 ± 0.04). Results differed from previous estimates of Φ for this species as our estimates of Φ were higher for both males and females compared to estimates from another breeding site and two nonbreeding locations. Disparity among Φ estimates from breeding and nonbreeding areas highlights the need to delineate site-specific factors throughout the annual cycle that influence population dynamics of the Western Sandpiper

APPARENT SURVIVAL OF BREEDING WESTERN SANDPIPERS ON THE YUKON-KUSKOKWIM RIVER DELTA, ALASKA

We used 8 years of live recapture data (1998–2005) to estimate apparent annual survival for male (n = 237) and female (n = 296) Western Sandpipers (Calidris mauri) breeding on a 36-ha plot on the Yukon-Kuskokwim River Delta, western Alaska. Apparent annual survival (Φ) is the product of true survival and site fidelity, and estimates of Φ were corrected for the probability of encounter. Overall return rates (individual returned to the study site in a subsequent season) were lower for females (40%) than males (65%), as was Φ (± SE, females = 0.65 ± 0.05, males = 0.78 ± 0.03), and encounter rate (females = 0.51 ± 0.07, males = 0.74 ± 0.04). Results differed from previous estimates of Φ for this species as our estimates of Φ were higher for both males and females compared to estimates from another breeding site and two nonbreeding locations. Disparity among Φ estimates from breeding and nonbreeding areas highlights the need to delineate site-specific factors throughout the annual cycle that influence population dynamics of the Western Sandpiper

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

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

A circumpolar study unveils a positive non-linear effect oftemperature on arctic arthropod availability that may reduce therisk of warming-induced trophic mismatch for breeding shorebirds

Seasonally abundant arthropods are a crucial food source for many migratorybirds that breed in the Arctic. In cold environments, the growth and emergence ofarthropods are particularly tied to temperature. Thus, the phenology of arthropodsis anticipated to undergo a rapid change in response to a warming climate, potentiallyleading to a trophic mismatch between migratory insectivorous birds and their prey.Using data from 19 sites spanning a wide temperature gradient from the Subarcticto the High Arctic, we investigated the effects of temperature on the phenology andbiomass of arthropods available to shorebirds during their short breeding seasonat high latitudes. We hypothesized that prolonged exposure to warmer summertemperatures would generate earlier peaks in arthropod biomass, as well as higherpeak and seasonal biomass. Across the temperature gradient encompassed by ourstudy sites (>10°C in average summer temperatures), we found a 3-day shift inaverage peak date for every increment of 80 cumulative thawing degree-days.Interestingly, we found a linear relationship between temperature and arthropodbiomass only below temperature thresholds. Higher temperatures were associatedwith higher peak and seasonal biomass below 106 and 177 cumulative thawingdegree-days, respectively, between June 5 and July 15. Beyond these thresholds,no relationship was observed between temperature and arthropod biomass. Ourresults suggest that prolonged exposure to elevated temperatures can positivelyinfluence prey availability for some arctic birds. This positive effect could, in part,stem from changes in arthropod assemblages and may reduce the risk of trophicmismatch. Sarctic arthropods, arctic breeding shorebirds, climate warming, insectivorous birds,invertebrate biomass, phenology, trophic mismatcpublishedVersio

A global threats overview for Numeniini populations: synthesising expert knowledge for a group of declining migratory birds

The Numeniini is a tribe of thirteen wader species (Scolopacidae, Charadriiformes) of which seven are near-threatened or globally threatened, including two critically endangered. To help inform conservation management and policy responses, we present the results of an expert assessment of the threats that members of this taxonomic group face across migratory flyways. Most threats are increasing in intensity, particularly in non-breeding areas, where habitat loss resulting from residential and commercial development, aquaculture, mining, transport, disturbance, problematic invasive species, pollution and climate change were regarded as having the greatest detrimental impact. Fewer threats (mining, disturbance, problematic native species and climate change) were identified as widely affecting breeding areas. Numeniini populations face the greatest number of non-breeding threats in the East Asian-Australasian Flyway, especially those associated with coastal reclamation; related threats were also identified across the Central and Atlantic Americas, and East Atlantic flyways. Threats on the breeding grounds were greatest in Central and Atlantic Americas, East Atlantic and West Asian flyways. Three priority actions were associated with monitoring and research: to monitor breeding population trends (which for species breeding in remote areas may best be achieved through surveys at key non-breeding sites), to deploy tracking technologies to identify migratory connectivity, and to monitor land-cover change across breeding and non-breeding areas. Two priority actions were focused on conservation and policy responses: to identify and effectively protect key non-breeding sites across all flyways (particularly in the East Asian - Australasian Flyway), and to implement successful conservation interventions at a sufficient scale across human-dominated landscapes for species’ recovery to be achieved. If implemented urgently, these measures in combination have the potential to alter the current population declines of many Numeniini species and provide a template for the conservation of other groups of threatened species