Tracking changes in migration for Vaux's swifts and chimney swifts using community science

Climate change has resulted in changes to weather patterns with earlier springs in temperate zones, warmer winters, and more frequent droughts and high-intensity storms. These changes present challenges to migrating bird species if they are unable adjust to the changing environment. In Chapter 2, using an extensive database of observations from citizen scientists, I asked if Vaux’s Swifts (Chaetura vauxi) altered their first arrival dates (date the first swift arrived) and peak roost occupancy dates (date the maximum number of swifts were observed at a roost) over a ten year period. I also asked if they altered migration timing in response to weather conditions experienced at migratory roosts during both spring and fall. The migration data analyzed was provided by the community science organization, Vaux’s Happening over a 10-year period from 2008-2017. In spring, first arrival and peak roost occupancy advanced over time, and first arrival advanced with an increase in local wind gust speeds. During fall migration, timing did not change over time, but higher temperatures were associated with later first arrival and peak roost occupancy. Also, higher local wind speeds were associated with earlier peak roost occupancy dates. These findings may indicate that Vaux’s Swifts are tracking earlier onset of spring conditions, as well as altering migration timing in response to weather conditions experienced during migration, especially during fall. In Chapter 3, I asked if Vaux’s Swifts and Chimney Swifts (Chaetura pelagica) changed their breeding distribution, migration routes, timing of migration, or speed of migration over time. The migration data analyzed was provided by eBird and covered the years 2009-2018. My results indicate a south-east shift in the breeding centroid for Vaux’s Swifts and a western shift in the breeding centroid for Chimney Swifts, as well as an eastern shift in the migration route for Vaux’s Swifts, almost equal in magnitude to its eastern breeding range shift. I also found an advance in the start of spring migration for Vaux’s Swifts and a delay in the start of fall migration for Chimney Swifts. Similar to my findings in Ch. 2, these results, using a much larger community-science dataset, may similarly indicate a response to earlier onset of spring conditions, and a possible delay in the onset of fall conditions. Surprisingly, my results also indicate a shift in breeding range to a more iii central location in North America (i.e., east for Vaux’s Swifts, west for Chimney Swifts) for both species, possibly as a result of anthropogenic changes to the environment. Results from both chapters indicate that the species show some behavioural plasticity in response to changing weather conditions and, likely, changes in the environment. What remains unclear is whether these species will be able to keep up with more extreme changes in weather and climate predicted with climate change.