Abstract:
The Cerulean Warbler (Setophaga cerulea) is a small, Neotropical migrant songbird that
breeds in central and eastern United States, and southern Canada. This species has experienced a
significant decline in population, and there are important gaps in our knowledge of this species’
biology. This research was intended to identify characteristics of Cerulean Warbler space use
and phenology. Two types of space use, the territory and the home range, have both been
studied for the Cerulean Warbler. However, studies differed in tracking methodologies, and a
fair comparison between the territory and home range cannot be made. I used radio telemetry to
track adult male Cerulean Warblers that were affixed with a radio-transmitter. I compared
resulting territory and home range estimates for each bird to identify the relationship between
these two space use areas. I also compared my resulting territory estimate with a previously
published territory estimate, which used an alternative tracking method (spot-mapping), to
determine if tracking methods have an effect on territory estimates. Cerulean Warbler home
range estimates (n = 14, mean ± SE = 2.33 ± 0.29 ha) were significantly larger than territory
estimates (n = 14, mean ± SE = 1.79 ± 0.39 ha). The telemetry-based territory estimates were
significantly larger than the published territory estimate (mean = ~0.70 ha). Climate change is
affecting the phenology of many species. I examined trends in Cerulean Warbler arrival timing
to Indiana from 1982-2019. I also compared arrival and breeding phenologies with several
climate variables. Cerulean Warblers did not advance their arrival timing significantly (1-4
days), while growing degree day accumulation indicates that spring conditions in Indiana have
advanced by ~14 days. Migratory phenology was best predicted by growing degree days, but
breeding phenology was not associated with any climate variable.
