Environmental conditions in winter and their ecological and evolutionary consequences for American redstarts (Setophaga ruticilla)

I used both observational and experimental approaches to assess the causes of nonbreeding habitat quality and to evaluate their ecological and evolutionary consequences for a Neotropical-Nearctic migratory bird, the American redstart (Setophaga ruticilla). Relative to control birds overwintering in second-growth scrub, redstarts experimentally upgraded from scrub to mangrove forest incorporated mangrove stable-carbon isotope signatures, maintained mass over winter, departed earlier on spring migration, and had higher apparent annual survival. Significantly higher arthropod biomass on upgrade territories implicated food availability as a proximate mechanism of habitat quality. Food availability, body condition, and spring departure schedules also depended on nonbreeding season rainfall. Food availability in mangrove was higher than in scrub in three of four years, allowing birds in this habitat to maintain superior body condition and depart earlier on spring migration. Abundant rainfall in a single year led to abnormally high food availability in scrub and early departure of birds in both habitats, suggesting both the amount and timing of rainfall influenced nonbreeding performance. Habitat occupancy and annual variation in rainfall had significant consequences for natal dispersal and selection through annual survival. Stable-hydrogen isotope ratios (δD) in feathers of immature birds captured again as adults indicated that habitat use in the first nonbreeding season interacted with spring phenology on temperate breeding grounds to influence the distance traveled on the first spring migration and direction of natal dispersal. In contrast, adults showed site fidelity between breeding seasons, suggesting nonbreeding conditions did not affect breeding dispersal and that migration distance becomes fixed later in life. Patterns of δD also revealed directional selection for short migration distance to southern breeding areas, a pattern that was nearly twice as strong in scrub compared to mangrove. During dry winters, redstarts experienced stabilizing selection on departure dates and directional selection for short migration. In years of high rainfall, birds experienced correlational selection favoring late departure when in good body condition. Thus, occupancy of moist habitats and years of high rainfall relaxed selection against late departure and longer migration. Collectively, these findings emphasize the need to understand how events throughout the annual cycle interact to shape fundamental biological processes

Challenging claims in the study of migratory birds and climate change

Recent shifts in phenology in response to climate change are well established but often poorly understood. Many animals integrate climate change across a spatially and temporally dispersed annual life cycle, and effects are modulated by ecological interactions, evolutionary change and endogenous control mechanisms. Here we assess and discuss key statements emerging from the rapidly developing study of changing spring phenology in migratory birds. These well-studied organisms have been instrumental for understanding climate-change effects, but research is developing rapidly and there is a need to attack the big issues rather than risking affirmative science. Although we agree poorly on the support for most claims, agreement regarding the knowledge basis enables consensus regarding broad patterns and likely causes. Empirical data needed for disentangling mechanisms are still scarce, and consequences at a population level and on community composition remain unclear. With increasing knowledge, the overall support (‘consensus view’) for a claim increased and between-researcher variability in support (‘expert opinions') decreased, indicating the importance of assessing and communicating the knowledge basis. A proper integration across biological disciplines seems essential for the field's transition from affirming patterns to understanding mechanisms and making robust predictions regarding future consequences of shifting phenologies

Rapid population decline in migratory shorebirds relying on Yellow Sea tidal mudflats as stopover sites

Migratory animals are threatened by human-induced global change. However, little is known about how stopover habitat, essential for refuelling during migration, affects the population dynamics of migratory species. Using 20 years of continent-wide citizen science data, we assess population trends of ten shorebird taxa that refuel on Yellow Sea tidal mudflats, a threatened ecosystem that has shrunk by >65% in recent decades. Seven of the taxa declined at rates of up to 8% per year. Taxa with the greatest reliance on the Yellow Sea as a stopover site showed the greatest declines, whereas those that stop primarily in other regions had slowly declining or stable populations. Decline rate was unaffected by shared evolutionary history among taxa and was not predicted by migration distance, breeding range size, non-breeding location, generation time or body size. These results suggest that changes in stopover habitat can severely limit migratory populations

Land Cover and Rainfall Interact to Shape Waterbird Community Composition

Human land cover can degrade estuaries directly through habitat loss and fragmentation or indirectly through nutrient inputs that reduce water quality. Strong precipitation events are occurring more frequently, causing greater hydrological connectivity between watersheds and estuaries. Nutrient enrichment and dissolved oxygen depletion that occur following these events are known to limit populations of benthic macroinvertebrates and commercially harvested species, but the consequences for top consumers such as birds remain largely unknown. We used non-metric multidimensional scaling (MDS) and structural equation modeling (SEM) to understand how land cover and annual variation in rainfall interact to shape waterbird community composition in Chesapeake Bay, USA. The MDS ordination indicated that urban subestuaries shifted from a mixed generalist-specialist community in 2002, a year of severe drought, to generalist-dominated community in 2003, of year of high rainfall. The SEM revealed that this change was concurrent with a sixfold increase in nitrate-N concentration in subestuaries. In the drought year of 2002, waterbird community composition depended only on the direct effect of urban development in watersheds. In the wet year of 2003, community composition depended both on this direct effect and on indirect effects associated with high nitrate-N inputs to northern parts of the Bay, particularly in urban subestuaries. Our findings suggest that increased runoff during periods of high rainfall can depress water quality enough to alter the composition of estuarine waterbird communities, and that this effect is compounded in subestuaries dominated by urban development. Estuarine restoration programs often chart progress by monitoring stressors and indicators, but rarely assess multivariate relationships among them. Estuarine management planning could be improved by tracking the structure of relationships among land cover, water quality, and waterbirds. Unraveling these complex relationships may help managers identify and mitigate ecological thresholds that occur with increasing human land cover

SNAPSHOT USA 2019 : a coordinated national camera trap survey of the United States

This article is protected by copyright. All rights reserved.With the accelerating pace of global change, it is imperative that we obtain rapid inventories of the status and distribution of wildlife for ecological inferences and conservation planning. To address this challenge, we launched the SNAPSHOT USA project, a collaborative survey of terrestrial wildlife populations using camera traps across the United States. For our first annual survey, we compiled data across all 50 states during a 14-week period (17 August - 24 November of 2019). We sampled wildlife at 1509 camera trap sites from 110 camera trap arrays covering 12 different ecoregions across four development zones. This effort resulted in 166,036 unique detections of 83 species of mammals and 17 species of birds. All images were processed through the Smithsonian's eMammal camera trap data repository and included an expert review phase to ensure taxonomic accuracy of data, resulting in each picture being reviewed at least twice. The results represent a timely and standardized camera trap survey of the USA. All of the 2019 survey data are made available herein. We are currently repeating surveys in fall 2020, opening up the opportunity to other institutions and cooperators to expand coverage of all the urban-wild gradients and ecophysiographic regions of the country. Future data will be available as the database is updated at eMammal.si.edu/snapshot-usa, as well as future data paper submissions. These data will be useful for local and macroecological research including the examination of community assembly, effects of environmental and anthropogenic landscape variables, effects of fragmentation and extinction debt dynamics, as well as species-specific population dynamics and conservation action plans. There are no copyright restrictions; please cite this paper when using the data for publication.Publisher PDFPeer reviewe

GBIF.org

Data were acquired from GBIF.org and were used to generate a habitat suitability surface for the common green darner (Anax junius). Citation: GBIF.org (03 July 2018) GBIF Occurrence Download https://doi.org/10.15468/dl.pw0uo

Observed Flight dates

This file contains the first flight date information for adult Common green darners (Anax junius) used to generate Fig 1

Green Darner Isotope data

This file contains isotope data used to make natal geographic assignments to reveal the annual cycle and migration of the Common green darner (Anax junius)