Research

Migration, ecophysiology, and genomic divergence along elevational gradients 

High elevations push organisms to their physiological limits. I study how elevation shapes migration, physiology, and genomic change in birds with a focus on birds that make 'extreme' elevational migrations of 2,000 meters or more between the breeding and non-breeding seasons. In a recent global analysis of >4 million occurrence records, I identified 105 taxa from 29 families and 10 orders worldwide that make these types of extreme elevational shifts, a behavior that I described, called elevational niche-shift migration (ENSM). I am interested in the functional genetic consequences of extreme elevational shifts and the extent to which such shifts are associated with diversification. I study these topics across the bird tree, with a particular focus on giant hummingbirds (Patagona gigas). Since 2017, I have tracked Giant Hummingbird migration using miniaturized devices and a lightweight backpack tracking harness that I designed. I integrate migration data with whole genomes, blood and morphology data from wild-caught individuals, and DNA from historical museum specimens to answer questions about migratory connectivity, population genomics, evolutionary history, ecophysiology, and diversification




Genomic-phenomic convergence of extreme elevational migration

Repeated evolution of extreme elevational migration is a pervasive but understudied example of parallel evolution, and the physiological basis of the behavior is poorly understood. I combine comparative genomics and transcriptomics with field physiological experiments to study genetic adaptation, physiological plasticity, and gene expression of extreme elevational migrants in the tropical Andes and temperate Himalayas. This work is being done in collaboration with the Cornell University Museum of Vertebrates, the Museum of Southwestern Biology, and Centro de Ornitología y Biodiversidad (CORBIDI) in Peru. 

Adaptation to mountain environments

Low oxygen pressure at high elevations is a strong environmental stressor. My work examines how blood traits that underpin blood-oxygen carrying capacity vary across short timescales of acclimatization and long timescales of adaptation, as well as how elevational specialists and generalists differ in their genetic adaptations and physiological profiles. I study these topics across diverse clades, such as songbirds and hummingbirds, by combining field sampling, molecular techniques, and phylogenetic comparative approaches. My work has shown that evolutionary solutions to reduced oxygen availability can occur in fundamentally similar ways across individual and phylogenetic timescales, suggesting that 'rules' of elevational variation in blood-oxygen carrying capacity are set by the physics of gas exchange. Additionally, species differences in elevational range matter when examining underlying mechanisms of blood-oxygen carrying capacity adjustment, highlighting unique aspects of species adaptation at extreme elevations.



Host-parasite community dynamics across space and time

Parasites are important drivers of species distributions and diversity. I study malaria-causing haemosporidian blood parasites and their avian hosts to understand community structure, patterns of turnover, and the effects of shifting climatic conditions on host-parasite ranges. My work encompasses community-level surveys of parasite composition in both mountain and island systems, host specificity in breeding birds distributed along environmental gradients in the southwestern USA and Peru, as well as detailed examination of host-parasite relationships in single species and clades, such as Audubon's Warblers (Setophaga auduboni) and vireos (family: Vireonidae), using phylogenetic models and genomic tools. My research suggests that interactions among hosts and parasites can reciprocally limit individual species ranges and have 'trickle up' effects to shape the composition of entire communities. 

Behavior and natural history of birds

Data on behavior and natural history are essential for understanding species' ecologies, interactions, population connectivity, and resilience in the face of climate change. I integrate field data with information from natural history specimens to understand these topics. My work has documented evolutionarily-puzzling hybrids, such as a Yellow x Black-throated Blue warbler and the scarlet "grosserbeak", previously undescribed brood parasitism and rangewide overlap between the Olive Warbler and Brown-headed Cowbird, and unusual 'skyscraper' nesting behavior of coastal marsh birds. In the neotropics, my research has contributed to our understanding of biology and behavior of data deficient species, such as the Golden-plumed Parakeet (Leptosittaca branickii) and the Andean Ibis (Theristicus branickii). Closer to home, I regularly submit records of rare or unusual bird sightings ornithological society rare birds records committees. This documentation complements eBird checklist observation details and makes occurrence records more accessible to diverse audiences.

Collaborators 

Banner Photo: Will Ford