Effective wildlife management requires identifying which species, or populations, may be vulnerable to climate-driven phenological mismatch. Critical knowledge gaps remain, however, about the underlying genetic and environmental factors that affect the adaptive potential of populations to shift phenology. The project team addressed these gaps by accomplishing four objectives. First, they conducted a large-scale investigation of the demographic consequences of phenological mismatch on a migratory bird, the American kestrel (Falco sparverius). Second, they investigated the genetic variants associated with the nesting and migration phenology of kestrels. Third, they developed an individual-based simulation model to test hypotheses about mechanisms underlying phenology shifts. They used American Kestrels as a focal species for these objectives because western Kestrels show evidence of phenology shifts (i.e., are nesting earlier) whereas eastern Kestrels do not. Finally, they parameterized the model for a Department of Defense (DoD) Partners in Flight (PIF) Mission-Sensitive Species, the Burrowing Owl (Athene cunicularia), and a DoD PIF Tier 2 species, Canada Warblers (Cardellina canadensis).

The project team added avian monitoring capacity at several DoD installations and leveraged research networks to sample American Kestrels’ environmental, phenological, demographic, and genetic information across their entire North American range. These data were used to develop SCOPE (Simulation of Carry-Over and Phenological Effects), an individual based model to test hypotheses about phenology shifts in response to climate change. Once SCOPE was developed, the project team used published research and data mining approaches to parameterize SCOPE for Canada Warblers and Burrowing Owls.

Western Kestrels had concomitant declines in reproduction and survival during the breeding season, whereas eastern Kestrels showed seasonal trade-offs between reproduction and survival, with early nesters having higher productivity and lower survival than later nesters. The project team identified genetic variants within candidate genes that modulate the circannual rhythms of American Kestrels. Genetic variants showed both multi- and single-gene effects on the timing of nesting and migration passage. Further, heterozygosity at individual loci of candidate genes differed between western Kestrels and eastern Kestrels. However, when population-specific genotypes were seeded in SCOPE, genetic composition and diversity had only very small effects on nesting phenology shifts. Alternatively, results from SCOPE showed that seasonal declines in adult survival, as well as competition for nest sites and mates, were strong drivers of earlier nesting. Finally, results from the Canada Warbler SCOPE model showed that their nesting phenology did not keep pace with climate-driven advances in spring, suggesting that they are vulnerable to mismatch. Burrowing Owl SCOPE results suggested they might be resilient to mismatch.

Results suggest that large populations lacking seasonal trade-offs in reproduction and survival are likely to be resilient to phenological mismatch. Alternatively, populations that have seasonal trade-offs between reproduction and survival, declining populations where density dependent processes like competition for nest sites and mates is lower, or small populations with limited genetic potential are likely to be vulnerable to mismatch. Genetic results suggest that future research on the genes that modulate the metabolic and light input pathways to biological clocks will be helpful for revealing variants associated with phenology. Finally, the project team provided methodological approaches for integrating genetic and ecological information into models that simulate both evolutionary and ecological processes, which is an important advancement for understanding and predicting population responses to environmental change and increases the understanding of the mechanisms underlying phenology shifts.