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Raptor Research

Photo by C. Olson

Click on the title for a pdf file of the paper

Differential winter distribution of Rough-legged Hawks by sex in western North America

We conducted roadside surveys of Rough-legged Hawks in Montana, California, and Nevada for four consecutive winters.  The ratio of males to females was significantly lower in Montana than in the southerly locations, suggesting that females wintered farther north than males.  We did not detect differential winter distribution by age and the sex ratios of juveniles trapped in Montana were nearly identical to ratios observed for adults.  We suggest that thermal regulation is an important factor influencing differential winter distribution in Rough-legged Hawks.

Dispersal movements of juvenile Mexican Spotted Owls in New Mexico

We used tail-mounted radio transmitters to track the dispersal movements of juvenile and sub-adult Mexican Spotted Owls in New Mexico.  Juveniles exhibited two types of dispersing behavior: moving rapidly across the landscape (up to 11.3 km/night) and extensive local exploration.  Two juveniles moved between separate mountain ranges crossing at least 25 km of grassland and pinyon-juniper savannah habitat, suggesting that isolated populations in the southwest U.S. could function as metapopulations.  During dispersal, juveniles roosted in habitat unlike that normally used by breeding adults.  The sub-adult females paired temporarily with adult males in their first summer, but did not breed and left in the fall, suggesting that dispersal can continue through an owl's second year.

Genetics Research

I worked under Dr. Mary Peacock, a geneticist and Assistant Professor in the Department of Biology, on these three DNA fingerprinting projects.  We collaborated with graduate students (Dr. David Delehanty, Dr. Scott Fleury), professors (Dr. Guy Hoelzer, Dr. Stephen St. Jeor), and visiting scientists (Dr. Pascal Villard) at the University of Nevada-Reno.

Population genetic structure and parentage in migratory Red-naped Sapsuckers in a naturally fragmented environment

We used DNA fingerprinting to estimate genetic differentiation among Red-naped Sapsuckers breeding in naturally fragmented riparian aspen forest in five canyons of the Toiyabe Range, central Nevada.  Sapsucker breeding habitat in the Great Basin is patchy and isolated and many populations in Nevada were extirpated during the early 20^th century because aspen trees were cut for mining operations.  In fact, Red-naped Sapsuckers may have been extirpated from the Toiyabes prior to 1940.  Our genetic results suggest that frequent gene flow occurred among canyons, which was supported by direct observations of natal and breeding dispersal.  This indicates that extirpated populations may have been rapidly re-colonized once suitable breeding habitat regenerated.

Habitat loss, dispersal, and genetic variation in an endemic island woodpecker

We used DNA fingerprinting and mark-resight to investigate genetic population structure, the relatedness of mated pairs, and dispersal patterns of the Guadeloupe Woodpecker.  This species is endemic to Guadeloupe and is only found in the forests on the two largest islands.  Our DNA fingerprinting results suggest that dispersal and gene flow occurred between the two islands, but there was a moderate degree of genetic differentiation.  Mark/re-sight results also suggested that dispersal was limited.  Some breeding occurred between first order relatives within both island populations.  Continued habitat loss and fragmentation on the smaller island will further reduce the total population size and may have profound effects on population persistence and maintenance of genetic variation.

Fidelity to Mojave Desert water sites results in Mountain Quail population genetic structure

We measured population genetic structure of Mountain Quail breeding in the Mojave Desert of southern California.  In arid areas, Mountain Quail cluster around water sources such as springs and wildlife guzzlers during the breeding season.  Previous studies indicate Mountain Quail have high site fidelity within and between years.  Mountain Quail in the Mojave are not found in a naturally fragmented environment, yet the quail we sampled showed genetic structure at the small geographic scale of this study.  We suggest that genetic structure is not due to habitat barriers but rather results from the physiological need for water and the behavioral tendency of Mountain Quail to gather and breed near their natal water source.

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