Winter ecology of migratory grassland birds

Grassland habitats of the Southern Great Plains provide key wintering habitats for migratory songbirds, particularly longspurs of the Family Calcariidae. A number of these species have experienced population declines over the past 50 years. Such losses may be partly driven by mortality on wintering grounds or degraded post-winter body condition causing negative carry-over effects during breeding, yet we lacked data on the winter ecology of these species to make such determinations.

From the fall of 2018 through the spring of 2020, PhD students John Muller and Nu Perera investigated the habitat usage and flock dynamics of three focal species of longspur wintering in Oklahoma: the Chestnut-collared Longspur (Calcarius ornatus), Smith’s Longspur (Calcarius pictus), and McCown’s Longspur (Rhynchophanes mccownii). Our purpose was three-fold:

  1. Assess habitat use of each species through standardized surveys and use this data to inform species distribution models.
  2. Track individual movements using radio telemetry to assess temporal associations with vegetation cover as well as the behavioral ecology of flocking behaviors relative to local weather conditions.
  3. Develop models of survivorship relative to land-use patterns in order to build projections for each species provided possible landscape-scale shifts in the future.
Wintering Chestnut-collared Longspurs in flight over snowy grassland
Chestnut-collared Longspurs flush from snow covered feeding sites in the Wichita Mountains, Comanche County, Oklahoma – January 3, 2019 [John Muller]