ARTE LTJA oxidative stress and migration
Description
Eight Long-tailed jaegers (LTJA) (four nesting pairs, 4 males and 4 females) were captured, sampled, and fitted with satellite tags. We captured six individuals in sub-Arctic alpine tundra habitat in Denali National Park and Preserve, Alaska, USA and two individuals in tundra habitat of the Arctic coastal plain near Alpine Alaska, USA . We attached 5-g Argos solar-powered satellite tags (Microwave Telemetry Inc.). Ten Arctic Terns (ARTE) (4 females, 2 males, 4 unknown) were captured in coastal tundra near Alpine, Alaska, USA. Six individuals were previously captured in 2017 and tracked with 0.65g archival light-level geolocators (Migrate Technology Ltd.). For ARTE, the migratory portion of the pathway was previously calculated in (Wong et al., 2022; Polar Biology (2022) 45:909–922; https://doi.org/10.1007/s00300-022-03043-2). For LTJA, we applied a change point analysis to a time series of net squared displacement to segment the track into breeding, migratory and non-breeding periods of the annual cycle. Net squared displacement is the distance from colony of each location, squared. We used the geodist package in R to calculate NSD using the square of vincenty distances from colony, estimated for an ellipsoid Earth. A change point analysis, implemented with the changepoint package in R, identifies changes in the rate of change of NSD and suggests segment breaks, which we then manually reviewed and assigned to a period of the annual cycle based on date. Light-level and sea-surface temperature data recorded by geolocator tags carried by ARTE were processed using the R statistical computing program packages TwGeos and SGAT. When light-level is the same across the globe, or does not vary during a day, locations cannot be resolved. Therefore, Arctic Tern migration paths are truncated; movements in the Arctic Circle for some individuals were unavailable. Argos satellite data for LTJA were processed using a continuous-time movement model following details in (Harrison et al., 2021; Eco & Evo (2021) 12:e8451 DOI: 10.1002/ece3.8451 and implemented in package foieGras for R. We sampled blood (~ 0.5 mL) from the brachial vein and collected into a heparinized microcentrifuge tube after birds were fitted with bands and tags and prior to release. Samples were stored on ice until return to the field station. Upon return to the field station, we measured hematocrit, aliquoted whole blood to hemoglobin reagents (see below) and separated plasma by centrifuge at 12000 rpm for 5 minutes. Plasma samples were frozen at -20 ⁰C until shipped on dry ice to Massachusetts, where they were stored at -80 ⁰C until laboratory analysis. Hemoglobin samples were protected from light and refrigerated until analysis. Birds were restrained for 32-60 minutes prior to blood sampling for tag application. Plasma samples were analyzed after the assays described in Fowler et al. 2018 Frontiers in Zoology (2018) 15:45; https://doi.org/10.1186/s12983-018-0288-3