ABSTRACT. We describe a new collaborative network, the Motus Wildlife Tracking System (Motus; https://motus.org), which is an international network of researchers using coordinated automated radio-telemetry arrays to study movements of small flying organisms including birds, bats, and insects, at local, regional, and hemispheric scales. Radio-telemetry has been a cornerstone of tracking studies for over 50 years, and because of current limitations of geographic positioning systems (GPS) and satellite transmitters, has remained the primary means to track movements of small animals with high temporal and spatial precision. Automated receivers, along with recent miniaturization and digital coding of tags, have further improved the utility of radio-telemetry by allowing many individuals to be tracked continuously and simultaneously across broad landscapes. Motus is novel among automated arrays in that collaborators employ a single radio frequency across receiving stations over a broad geographic scale, allowing individuals to be detected at sites maintained by others. Motus also coordinates, disseminates, and archives detections and associated metadata in a central repository. Combined with the ability to track many individuals simultaneously, Motus has expanded the scope and spatial scale of research questions that can be addressed using radio-telemetry from local to regional and even hemispheric scales. Since its inception in 2012, more than 9000 individuals of over 87 species of birds, bats, and insects have been tracked, resulting in more than 250 million detections. This rich and comprehensive dataset includes detections of individuals during all phases of the annual cycle (breeding, migration, and nonbreeding), and at a variety of spatial scales, resulting in novel insights into the movement behavior of small flying animals. The value of the Motus network will grow as spatial coverage of stations and number of partners and collaborators increases. With continued expansion and support, Motus can provide a framework for global collaboration, and a coordinated approach to solving some of the most complex problems in movement biology and ecology.Le Système de suivi de la faune Motus : un réseau de recherche collaboratif visant à mieux comprendre le déplacement des animaux RÉSUMÉ. Le Système de suivi de la faune Motus (Motus; https://motus.org), un nouveau réseau collaboratif de chercheurs internationaux, repose sur un ensemble coordonné de stations automatisées de radiotélémétrie pour étudier le déplacement de petits organismes volant, comme les oiseaux, les chauves-souris et les insectes, aux échelles locales et régionales, et à celle de l'hémisphère. Pierre angulaire pour les études de suivi depuis plus de 50 ans, la radiotélémétrie est encore le principal moyen de suivre le déplacement de petits animaux avec une grande précision temporelle et spatiale, en raison des limites que présentent les émetteurs basés sur le système de positionnement géographique (GPS) ou satellite. Des stations réceptrices automatisées,...

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We compiled a >50‐year record of morphometrics for semipalmated sandpipers (Calidris pusilla), a shorebird species with a Nearctic breeding distribution and intercontinental migration to South America. Our data included >57,000 individuals captured 1972–2015 at five breeding locations and three major stopover sites, plus 139 museum specimens collected in earlier decades. Wing length increased by ca. 1.5 mm (>1%) prior to 1980, followed by a decrease of 3.85 mm (nearly 4%) over the subsequent 35 years. This can account for previously reported changes in metrics at a migratory stopover site from 1985 to 2006. Wing length decreased at a rate of 1,098 darwins, or 0.176 haldanes, within the ranges of other field studies of phenotypic change. Bill length, in contrast, showed no consistent change over the full period of our study. Decreased body size as a universal response of animal populations to climate warming, and several other potential mechanisms, are unable to account for the increasing and decreasing wing length pattern observed. We propose that the post‐WWII near‐extirpation of falcon populations and their post‐1973 recovery driven by the widespread use and subsequent limitation on DDT in North America selected initially for greater flight efficiency and latterly for greater agility. This predation danger hypothesis accounts for many features of the morphometric data and deserves further investigation in this and other species.

For most shorebird species, our understanding of the basic limiting factors and when or where they operate during the annual cycle is currently inadequate to either understand ongoing declines or effectively allocate conservation resources for recovery. Whimbrels (Numenius phaeopus) exhibit delayed recruitment and have low fecundity, and populations with such life-history traits are often vulnerable to increases in adult mortality. We tracked 33 adult Whimbrels with satellite transmitters for 12,802 bird-days to investigate patterns in survival and recorded 16 probable and 5 confirmed mortalities. We used Cox’s proportional hazards model to estimate daily hazard rates by season and a Kaplan-Meier product limit estimator to estimate monthly survival. Daily hazard rates varied by season and were 5 times higher during migratory periods (fall and spring migration) compared to stationary periods (winter and breeding). Estimated annualized survivorship was 0.54 ± 0.21 (SE) and on the lower end of the range of 0.8–0.9 believed to be required to maintain a stable population. More than half of the mortality recorded during the study occurred during the fall hunting season and within the last remaining area throughout the Western Hemisphere where significant legal and illegal hunting occurs. One-third of mortality occurred during spring migration either within terminal staging sites or as birds made final movements to breeding grounds. Survival during the migratory periods may have been influenced by the use of transmitters.

The Bay of Fundy, Canada is a critical migratory stopover for Semipalmated Sandpipers (Calidris pusilla) during fall migration. Recent ecological changes combined with range-wide population declines indicate that a re-evaluation of habitat use and regional fidelity is required. The Bay of Fundy is divided into three regions, each of which contains multiple foraging and roost sites. In this study, we examined local movement and regional fidelity within and between years using radio-telemetry and field-readable markers. We deployed 194 radio-transmitters and 2295 field-readable flags on Semipalmated Sandpipers during migration in 2013-2014, and resighted these birds, along with additional birds flagged in 2012, between 2013 and 2016. Radio-tracked birds used on average 1.3 to 4.1 foraging and roost sites per day, with most making multiple daily movements, but only 2% made permanent moves between geographically distant regions within the bay during stopover. Additionally, 97% of birds returned to their original region in subsequent years. The use of multiple sites suggests Semipalmated Sandpipers are capable of adapting to dynamic conditions in the Bay of Fundy on a local scale, but the high regional fidelity suggests that their ability to adapt to changes occurring at a regional scale may be limited. Uncertainty about the capability of Semipalmated Sandpipers to flexibly move among different regions of the Bay of Fundy supports the need for conservation at both the site and regional level. Fidélité régionale intra-et interannuelle des Bécasseaux semipalmés (Calidris pusilla) aux haltes migratoires dans le fond de la baie de Fundy, Canada RÉSUMÉ. La baie de Fundy, au Canada, représente une halte essentielle pour les Bécasseaux semipalmés (Calidris pusilla) durant la migration automnale. Une réévaluation de l'utilisation de l'habitat et de la fidélité régionale est nécessaire en raison de changements écologiques récents couplés aux diminutions de population à grande échelle. La baie de Fundy se divise en trois régions, chacune comptant de nombreux sites d'alimentation et de repos. Nous avons examiné les déplacements locaux et la fidélité régionale des bécasseaux au cours d'une même année et entre les années, au moyen de la radiotélémétrie et de marqueurs lisibles à distance sur le terrain. Nous avons posé 194 émetteurs radio et 2 295 marqueurs sur des Bécasseaux semipalmés durant les migrations de 2013 et 2014, et avons réobservé ces oiseaux de 2013 à 2016, en plus d'autres oiseaux munis de marqueurs en 2012. Les oiseaux suivis par radio ont utilisé de 1,3 à 4,1 sites d'alimentation et de repos en moyenne par jour, la plupart se déplaçant plusieurs fois quotidiennement, tandis que 2 % seulement se sont déplacés de façon permanente entre des régions distantes dans la baie en cours de halte. De plus, 97 % des oiseaux sont retournés dans leur région d'origine dans les années subséquentes. Le fait que les Bécasseaux semipalmés utilisent de multiples sites donne à penser qu'ils sont capables de s'adapter aux conditions dy...

Long-distance migrants are assumed to be more time-limited during the pre-breeding season compared to the post-breeding season. Although breeding-related time constraints may be absent post-breeding, additional factors such as predation risk could lead to time constraints that were previously underestimated. By using an automated radio telemetry system, we compared pre- and post-breeding movements of long-distance migrant shorebirds on a continent-wide scale. From 2014 to 2016, we deployed radio transmitters on 1,937 individuals of 4 shorebird species at 13 sites distributed across North America. Following theoretical predictions, all species migrated faster during the pre-breeding season, compared to the post-breeding season. These differences in migration speed between seasons were attributable primarily to longer stopover durations in the post-breeding season. In contrast, and counter to our expectations, all species had higher airspeeds during the post-breeding season, even after accounting for seasonal differences in wind. Arriving at the breeding grounds in good body condition is beneficial for survival and reproductive success and this energetic constraint might explain why airspeeds are not maximised in the pre-breeding season. We show that the higher airspeeds in the post-breeding season precede a wave of avian predators, which could suggest that migrant shorebirds show predation-minimizing behaviour during the post-breeding season. Our results reaffirm the important role of time constraints during northward migration and suggest that both energy and predation-risk constrain migratory behaviour during the post-breeding season.

Shorebirds are declining to a greater extent than many other avian taxa around the world. In North America, shorebirds, along with aerial insectivores and grassland birds, have some of the highest proportions of declining species of any group. Here, we apply a new hierarchical Bayesian model to analyze shorebird migration monitoring data from across North America, from 1980 to 2019, and present the most recent available estimates of trends for 28 species. Point estimates for survey-wide trends in abundance were negative for 26 of 28 species (93%). Despite challenges with low precision associated with migration count data, trends for 19 species had 95% credible intervals that were entirely negative. More than half of the species were estimated to have lost >50% of their abundance. Furthermore, estimated rates of decline have accelerated during the last three generations for most species. Point estimates of trend were more negative for 18 species (64%) during the most recent three-generation period in comparison to the previous three-generation period. Many species now exceed international criteria for threatened species listing. The analytic approach used here allows us to model regional variation in trends, although survey coverage and strength of inference were greatest in the eastern portions of North America (east of 100°W). We found the greatest declines at staging sites along the Atlantic Coast from North Carolina to Nova Scotia, and lesser declines along the Gulf Coast and in the midcontinental United States. The declines in shorebird populations reported here are worrisome and signal the urgent need for conservation action. In addition, it would be beneficial to validate these results through collection and analysis of complementary data, and to initiate demographic studies throughout the annual cycle to determine where and when declines are most likely to originate. This improved information will allow for development of more targeted efforts to reverse declines through conservation action.

Many long-distance migratory birds use habitats that are scattered across continents and confront hazards throughout the annual cycle that may be population-limiting. Identifying where and when populations spend their time is fundamental to effective management. We tracked 34 adult whimbrels (Numenius phaeopus) from two breeding populations (Mackenzie Delta and Hudson Bay) with satellite transmitters to document the structure of their annual cycles. The two populations differed in their use of migratory pathways and their seasonal schedules. Mackenzie Delta whimbrels made long (22,800 km) loop migrations with different autumn and spring routes. Hudson Bay whimbrels made shorter (17,500 km) and more direct migrations along the same route during autumn and spring. The two populations overlap on the winter grounds and within one spring staging area. Mackenzie Delta whimbrels left the breeding ground, arrived on winter grounds, left winter grounds and arrived on spring staging areas earlier compared to whimbrels from Hudson Bay. For both populations, migration speed was significantly higher during spring compared to autumn migration. Faster migration was achieved by having fewer and shorter stopovers en route. We identified five migratory staging areas including four that were used during autumn and two that were used during spring. Whimbrels tracked for multiple years had high (98%) fidelity to staging areas. We documented dozens of locations where birds stopped for short periods along nearly all migration routes. The consistent use of very few staging areas suggests that these areas are integral to the annual cycle of both populations and have high conservation value.