Smith, Paul A.

Migration, space use, and phenology play key roles in shaping avian populations and are therefore critical for conservation. My thesis examines the migration strategies and non-breeding spatial requirements of Virginia's beach-nesting American Oystercatchers (Haematopus palliatus), as well as the nesting phenology of mid-Atlantic American Oystercatchers and Piping Plovers (Charadrius melodus). I assessed migratory decisions using field-readable bands and GPS transmitters, finding that ~90% of Virginia's beach-nesting American Oystercatchers migrate out-of-state during the non-breeding season, though tested hypotheses did not strongly predict migration patterns. I then estimated home range sizes of American Oystercatchers during the non-breeding season, revealing high individual variation (12.1-201.6 km²) and a potential trend toward larger home ranges in males. Finally, I analyzed clutch initiation timing of American Oystercatchers and Piping Plovers in response to climate change, finding that American Oystercatchers advanced timing of breeding by 10.7 days between 2005-2022, while Piping Plovers showed no significant shift.

Author Keywords: behavioural ecology, climate change, home-range, migration, movement ecology, phenology

The Lesser Yellowlegs (Tringa flavipes) is a steeply declining shorebird that breeds across boreal North America. I studied nest survival in Anchorage, Alaska, USA and Churchill, Manitoba, Canada and nest site selection factors in Churchill. Nests were monitored at each site and daily nest survival rates (DSR) were calculated based on a maximum likelihood approach. Overall nest survival was ~63% for Anchorage (lcl–ucl = 0.450–0.773, n=49) and ~28% (lcl–ucl = 0.113–0.481, n=26) for Churchill. Earlier initiation dates, warmer mid-incubation temperatures and lower temperature variability during nesting were linked with higher DSR. I tested nest site selection at territorial and microhabitat scales using multiple logistic regression to compare nest sites with random points. Lesser Yellowlegs selected territories further from water and, at the microhabitat scale, taller shrubs. Projected climate-related shifts in weather and habitat will likely present both benefits and challenges to Lesser Yellowlegs.

Keywords: Lesser Yellowlegs, Tringa flavipes, shorebird, nest survival, nest success, nesting habitat, breeding habitat, boreal, sub-arctic, climate change, Anchorage, Alaska, Churchill, Manitoba

Author Keywords: boreal, breeding habitat, Lesser Yellowlegs, nest survival, shorebird, Tringa flavipes

I examined how shorebirds respond to environmental change at a key subarctic migratory bird stopover site, the southwestern coast of James Bay, Ontario, Canada. First, I investigated if the morphology of sandpipers using James Bay during southbound migration has changed compared to 40 years prior. I found shorter, more convex and maneuverable wings for sandpipers in the present-day compared to the historical monitoring period, which supports the hypothesis that wing length change is driven by increases in predation risk. Secondly, I assessed the relationship between migration distance, body condition, and shorebird stopover and migratory decisions. Species that travelled farther distances from James Bay to wintering areas migrated with more characteristics of a time-minimizing migration strategy whereas species that travelled shorter distances migrated with energy minimizing strategies. Body condition impacted length of stay, wind selectivity at departure, groundspeeds, and probability of stopover and detection in North America after departing James Bay. Thirdly, I examined annual variation in dry/wet conditions at James Bay and found that shorebirds had lower body mass in years with moderate drought. In the present-day, drought resulted in lower invertebrate abundance and refuelling rates of shorebirds during stopover, which led to shorter stopover duration for juveniles and a higher probability of stopover outside of James Bay for all groups except white-rumped sandpiper. Finally, I estimated the relative importance of intertidal salt marsh and flat habitats to the diets of small shorebirds and found that semipalmated and white-rumped sandpiper (Calidris pusilla and C. fuscicollis) and semipalmated plover (Charadrius semipalmatus) diets consist of ~ 40 – 75% prey from intertidal marsh habitats, the highest documented in the Western Hemisphere for each species. My research shows that James Bay is of high importance to white-rumped sandpipers, which are unlikely to stop in North America after departing James Bay en route to southern South America. Additionally, intertidal salt marsh habitats (and Diptera larvae) appear particularly important for small shorebirds in the region. My thesis shows that changing environmental conditions, such as droughts, can affect shorebird refuelling and stopover strategies.

Author Keywords: body condition, diet, environmental change, migration, ornithology, stopover ecology