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UC Davis Natural Reserve System

Natural History Handbook of Stebbins Cold Canyon Reserve

Holly Ernest prepares to weigh an Anna's Hummingbird.

Male Rufous Hummingbird in hand

A male Rufous Hummingbird in hand.


Anna's hummingbird at the trap.

Anna's humming bird at the trap.

Featured Research - McLaughlin Natural Reserve

Holly Ernest
Department of Population Health & Reproduction
School of Veterinary Medicine, UC Davis

Population health and conservation genetics of hummingbirds

Hummingbirds, found only in the Americas, comprise the second largest taxonomic family of birds (over 330 species), are important pollinators for many plants, and are the tiny flying jewels of the animal kingdom. As ubiquitous as hummingbirds in general may seem, a number of species are threatened or endangered (at least 49 species as of 2006, up from 29 species in 1999). One species that occurs in California, the Rufous Hummingbird, is listed on the Audubon/Partners in Flight top 20 birds of decline in North America. Not surprisingly (since these birds are so tiny and difficult to sample – imagine taking a blood sample from a 4 gram [less than the weight of a U.S. nickel] wiggly bird), very little is known about hummingbird population biology and health. To assess population status, predict future population viabilities, and plan conservation, key information is needed: genetic diversity, population structure, effective population sizes, identification of breeding populations, and causes of illness and death.

Holly Ernest is beginning to gather this information with the help of the McLaughlin Reserve, the international Hummingbird Monitoring Network (HMN), and others. Dr. Ernest, a wildlife veterinarian and ecological geneticist on faculty at the UC Davis School of Veterinary Medicine, is developing DNA markers to non-invasively test genetic composition of hummingbird populations using feather samples. She and her team of graduate students and technicians have applied the newest techniques in trace DNA analysis (tiny amounts of sample, such as with forensic cases) to study the genetic diversity over large landscapes in species including Yellow-billed magpies, Swainson’s Hawks, Great Gray Owls, mountain lions, sea otters, and wild pigs (read more at With no harm to the hummingbirds, a small number of tiny body feathers are collected during the banding process for DNA analysis.

Another part of the study is to assess the role that disease plays in the ecology of hummingbirds. Detailed bird banding records will be evaluated for clues that signal health issues in hummers. Working with the California Animal Health & Food Safety Laboratory, the UC Davis Veterinary Teaching Hospital, and Lindsay Wildlife Museum, bodies of hummingbirds that have died from window-strike or other traumas will be examined for presence of diseases and toxins.

Holly’s work with hummingbirds began in 2008 when she joined a team of reserve staff and volunteers who run an HMN banding station at McLaughlin every two weeks from March to October. Holly collects samples and data, gains experience toward her own future bird banding permit, and (most especially) experiences the joy of hummingbird biology and nature up close.