Biology ETDs

Publication Date

Summer 8-1-2024


Elevational gradients cause profound eco-climatic variation across short distances. Partial pressure of oxygen (PO2) is a severe challenge that organisms face at high elevations; due partly to specialization on PO2, most Neotropical bird species have narrow elevational ranges. However, a small fraction are elevational generalists that span sea level to high elevations, and a subset undertake extreme migratory journeys from low to high elevations biannually. My dissertation combines diverse approaches across levels of biological organization to understand how elevation impacts the ecology, evolution, physiology, and migration of montane birds. I examined ‘extreme’ elevational migration in birds worldwide, blood physiology of Andean hummingbirds, and migration, genomics, and phylogeography of the giant hummingbirds. I discovered that elevational niche-shift migration tends to evolve rarely and under specific circumstances; extreme elevational migrant species typically exhibit genetic adaptations associated with high elevation; hematological traits––except for the cell size-number tradeoff––typically vary predictably with elevation, both within and among species. Finally, extreme elevational migration can facilitate diversification, as appears to have occurred in the Giant Hummingbird.

Project Sponsors

American Museum of Natural History, American Ornithological Society, American Philosophical Society, Explorers Club, the National Science Foundation, Nuttall Ornithological Club, Society of Systematic Biologists, Wilson Ornithological Society, University of New Mexico (UNM) Biology Graduate Student Association, UNM Department of Biology, UNM Graduate and Professional Student Organization, and the UNM Latin American and Iberian Institute.




Andes; birds; blood; elevation; genomics; migration

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Christopher C. Witt

Second Committee Member

Jennifer A. Rudgers

Third Committee Member

Michael J. Andersen

Fourth Committee Member

Nadia D. Singh


Embargo until 2024.

Available for download on Thursday, August 01, 2024