Migratory network reveals unique spatial-temporal migration dynamics of Dunlin subspecies along the East Asian-Australasian Flyway.

Determining the dynamics of where and when individuals occur is necessary to understand population declines and identify critical areas for populations of conservation concern. However, there are few examples where a spatially and temporally explicit model has been used to evaluate the migratory dynamics of a bird population across its entire annual cycle. We used geolocator-derived migration tracks of 84 Dunlin (Calidris alpina) on the East Asian-Australasian Flyway (EAAF) to construct a migratory network describing annual subspecies-specific migration patterns in space and time. We found that Dunlin subspecies exhibited unique patterns of spatial and temporal flyway use. Spatially, C. a. arcticola predominated in regions along the eastern edge of the flyway (e.g., western Alaska and central Japan), whereas C. a. sakhalina predominated in regions along the western edge of the flyway (e.g., N China and inland China). No individual Dunlin that wintered in Japan also wintered in the Yellow Sea, China seas, or inland China, and vice-versa. However, similar proportions of the 4 subspecies used many of the same regions at the center of the flyway (e.g., N Sakhalin Island and the Yellow Sea). Temporally, Dunlin subspecies staggered their south migrations and exhibited little temporal overlap among subspecies within shared migration regions. In contrast, Dunlin subspecies migrated simultaneously during north migration. South migration was also characterized by individuals stopping more often and for more days than during north migration. Taken together, these spatial-temporal migration dynamics indicate Dunlin subspecies may be differentially affected by regional habitat change and population declines according to where and when they occur. We suggest that the migration dynamics presented here are useful for guiding on-the-ground survey efforts to quantify subspecies' use of specific sites, and to estimate subspecies' population sizes and long-term trends. Such studies would significantly advance our understanding of Dunlin space-time dynamics and the coordination of Dunlin conservation actions across the EAAF.

Simple Field Anesthesia for Free-Ranging Microtines.

Although physical restraint without anesthesia is a common way to immobilize microtines in field settings, tagging can cause pain and stress, and escape-response movements may reduce marking quality. To evaluate if inhaled isoflurane may be a tool to minimize these issues, we anesthetized free-ranging voles (Microtus and Myodes spp.) undergoing subcutaneous injection of a passive integrated transponder tag and dorsal fur clipping. We anesthetized 24 voles for short-duration anesthesia using two 0.2-mL isoflurane doses in a simple drop-chamber system. We used the first dose to induce unconsciousness and the second dose to immediately restore unconsciousness after the vole regained consciousness from the first dose. Median induction times were 54 s for the first dose (interquartile range [IQR], 47-61) and 50 s for the second dose (IQR, 38-55). Median recovery times were 33 s for the first dose (IQR, 26-60) and 62 s for the second dose (IQR, 35-104). No mortalities occurred during the holding period. The technique was simple, inexpensive, and effective. We therefore recommend using isoflurane delivered in a drop chamber when tagging or marking microtines in the field to improve handling.

Environmental and life-history factors influence inter-colony multidimensional niche metrics of a breeding Arctic marine bird.

Human industrialization has resulted in rapid climate change, leading to wide-scale environmental shifts. These shifts can modify food web dynamics by altering the abundance and distribution of primary producers (ice algae and phytoplankton), as well as animals at higher trophic levels. Methylmercury (MeHg) is a neuro-endocrine disrupting compound which biomagnifies in animals as a function of prey choice, and as such bioavailability is affected by altered food web dynamics and adds an important risk-based dimension in studies of foraging ecology. Multidimensional niche dynamics (MDND; δ13C, δ15N, THg; total mercury) were determined among breeding common eider (Somateria mollissima) ducks sampled from 10 breeding colonies distributed across the circumpolar Arctic and subarctic. Results showed high variation in MDND among colonies as indicated by niche size and ranges in δ13C, δ15N and THg values in relation to spatial differences in primary production inferred from sea-ice presence and colony migratory status. Colonies with higher sea-ice cover during the pre-incubation period had higher median colony THg, δ15N, and δ13C. Individuals at migratory colonies had relatively higher THg and δ15N, and lower δ13C, suggesting a higher trophic position and a greater reliance on phytoplankton-based prey. It was concluded that variation in MDND exists among eider colonies which influenced individual blood THg concentrations. Further exploration of spatial ecotoxicology and MDND at each individual site is important to examine the relationships between anthropogenic activities, foraging behaviour, and the related risks of contaminant exposure at even low, sub-lethal concentrations that may contribute to deleterious effects on population stability over time. Overall, multidimensional niche analysis that incorporates multiple isotopic and contaminant metrics could help identify those populations at risk to rapidly altered food web dynamics.

Behavioural responses of breeding arctic sandpipers to ground-surface temperature and primary productivity.

Most birds incubate their eggs, which requires time and energy at the expense of other activities. Birds generally have two incubation strategies: biparental where both mates cooperate in incubating eggs, and uniparental where a single parent incubates. In harsh and unpredictable environments, incubation is challenging due to high energetic demands and variable resource availability. We studied the relationships between the incubation behaviour of sandpipers (genus Calidris) and two environmental variables: temperature and a proxy of primary productivity (i.e. NDVI). We investigated how these relationships vary between incubation strategies and across species among strategies. We also studied how the relationship between current temperature and incubation behaviour varies with previous day's temperature. We monitored the incubation behaviour of nine sandpiper species using thermologgers at 15 arctic sites between 2016 and 2019. We also used thermologgers to record the ground surface temperature at conspecific nest sites and extracted NDVI values from a remote sensing product. We found no relationship between either environmental variables and biparental incubation behaviour. Conversely, as ground-surface temperature increased, uniparental species decreased total duration of recesses (TDR) and mean duration of recesses (MDR), but increased number of recesses (NR). Moreover, small species showed stronger relationships with ground-surface temperature than large species. When all uniparental species were combined, an increase in NDVI was correlated with higher mean duration, total duration and number of recesses, but relationships varied widely across species. Finally, some uniparental species showed a lag effect with a higher nest attentiveness after a warm day while more recesses occurred after a cold day than was predicted based on current temperatures. We demonstrate the complex interplay between shorebird incubation strategies, incubation behaviour, and environmental conditions. Understanding how species respond to changes in their environment during incubation helps predict their future reproductive success.

Rapid, non-destructive analysis of calcium and strontium in eggshells by WD-XRF.

We developed a simple method of analyzing the strontium (Sr) and calcium (Ca) content of intact eggshell samples in support of a broader study of how dietary Sr uptake impacts waterfowl eggshell quality. We used wavelength dispersive - x-ray fluorescence spectrometry (WD-XRF) to analyze eggshell pieces ranging in size from ∼6-mm2 fragments to intact half-shells. We verified this approach on a subset of reference shells by subjecting the same region and volume of shell material from which x-ray signals were measured to analysis by inductively-coupled plasma mass spectrometry (ICP-MS). An analysis of the sources of analytical uncertainty yielded total internal error estimates of ±0.3 and 5% relative for Ca and Sr, respectively, on the basis of which the chemistry of intact shell material analyzed by WD-XRF in this study is compared. The total external errors associated with the WD-XRF results of this study in relation to certified reference material (National Institute of Standards and Technology [NIST] 1400 [a bone ash]) are ±9 and 13.5% relative for Ca and Sr, respectfully (95% CL). Our results demonstrate this method is acceptably accurate and precise for many wildlife management applications. WD-XRF analysis is a quick and inexpensive alternative to traditional methods for determining eggshell Sr and Ca that require acid digestion, allowing for generation of larger datasets that might otherwise be cost-prohibitive, while preserving sample material intact.

Trace Elements in Sea Ducks of the Alaskan Arctic Coast: Patterns of Variation Among Species, Sexes, and Ages.

Climate change and increasing industrialization in the Arctic call for the collection of reference data for assessing changes in contaminant levels. For migratory birds, measuring and interpreting changes in trace element burdens on Arctic breeding areas require insights into factors such as sex, body size, or wintering area that may modify patterns independently of local exposure. In the Alaskan Arctic, we determined levels of trace elements in liver and kidney of common eiders (Somateria mollissima) and long-tailed ducks (Clangula hyemalis) from the Prudhoe Bay oil field and of king eiders (S. spectabilis) and threatened spectacled eiders (S. fischeri) and Steller's eiders (Polystica stelleri) from near the town of Barrow. Small-bodied Steller's eiders and long-tailed ducks from different locations had similarly low levels of selenium (Se), cadmium (Cd), and copper (Cu), perhaps reflecting high mass-specific rates of metabolic depuration during long spring migrations through areas of low exposure. In larger species, Se, Cd, and Cu concentrations were higher in adults than juveniles suggesting that these elements were acquired in nonbreeding marine habitats. Adult male spectacled eiders had exceptionally high Se, Cd, and Cu compared with adult females, possibly because of depuration into eggs and longer female occupancy of nonmarine habitats. Adult female common eiders and juvenile long-tailed ducks at Prudhoe Bay had high and variable levels of Pb, potentially due to local exposure. Explanations for substantial variations in Hg levels were not apparent. Further research into reasons for differing element levels among species and sexes will help clarify the sources, pathways, and risks of exposure.