Past Research

 

 

Phenotypic Variation in Buteos

Project Lead: Megan Mayo

The Harlan’s hawk (Buteo jamaicensis harlani) is a raptor that exhibits exceptionally high levels of phenotypic variation in tail plumage color and pattern, even when compared to a conspecific subspecies, the western red-tailed hawk, Buteo jamaicensis calurus. Phenotypic divergence between Harlan’s hawks, which breed mostly in Alaska, and western red-tailed hawks, which breed in the western US and Canada, is not due to reproductive isolation; a recent study documented ongoing gene flow between the two subspecies, highlighting the question of what mechanism is responsible for maintenance of the polymorphism in Harlan’s hawks. How is variation maintained in one subspecies but not another? Little is known about the mechanism responsible for continued existence of such variation, though recent research has indicated that the melanocortin 1 receptor, a gene that has been shown to control polymorphism in many mammal and bird species, does not control polymorphism in Harlan’s hawks.  

 

Megan Mayo UC Davis
Population Genetics of Rough-legged Hawks

Project Lead: Megan Mayo

The Rough-legged Hawk (Buteo lagopus) is a widespread, panboreal raptor found in North America, Europe, and Asia. Despite its widespread distribution, we know very little about population structure or connectivity and gene flow between continents. We are using NextGen sequencing to examine DNA from a combination of wintering and breeding individuals to describe phylogenetic and population level differences among rough-legged hawk  populations. Through multiple collaborations, we have collected samples from N. America, Europe, and Asia.

 

 UC Davis Josh Hull Megan Mayo
Megan Mayo UC Davis Brian Smithers
Bristlecone Pines and Limber Pines

Project Lead: Megan Mayo and Brian Smithers

Great Basin bristlecone pines (Pinus longaeva) are the oldest non-clonal species on earth. Despite the fact that many of these trees have survived thousands of years, we still know very little about population structure, gene flow, and local adaptation of these ancient pines. With global climate change come threats such as blister rust, increased fire, drought, and novel interspecific competition, all of which threaten the continued survival of these living fossils. Perhaps the most interesting, unpredictable, and rapidly changing of these factors is invasion of limber pines (Pinus flexilis) into historically exclusive P. longaeva habitat. P. flexilis is a widespread species generally found lower in elevation on granitic soils in the White Mountains, but within the past fifty years, it has begun to establish upslope on dolomitic soil, with new recruits within the past 20 years establishing within P. longaeva habitat on Big Horn Sheep Peak in the White Mountains.  Limber pines may be better adapted to take advantage of a rapidly changing climate, meaning that much bristlecone pine treeline could be dominated by limber pine in the near future.  It is unclear whether this recent colonization event is the result of global climate change or how P. longaeva will be affected.

 

Pisaster Seastars 

Project Lead: Megan Mayo and Grace Ha

Pisaster ochraceus is a keystone predator of the rocky intertidal. Ranging in color from brilliant purple to outrageous orange, they are as charismatic as they are voracious. While the variation in coloration is obvious, the genes responsible have not yet been identified. Using NextGen sequencing and captive feeding experiments, we are investigating the underlying gene or genes responsible for phenotypic polymorphism in Pisaster ochraceus. 

 

Megan Mayo UC Davis Grace Ha
Brian Prochazka UC Davis
Greater Sage Grouse

Project Lead: Brian Prochazka

The greater sage grouse (Centrocercus urophasianus) is a lekking species found in the Northwestern United States. For this species, we are 1) quantifying resource selection via GPS location data and dynamic brownian bridge movement models, 2) estimating risk associated with various land cover types via shared frailty models, 3) estimating the effects of wildfire over the last 30 years on population growth rates for 800+ leks located throughout the Great Basin, 4) estimating abundance via state-space models, and 5) quantifying winter resource selection; specifically, nutrient vs anti-nutrient acquisition/avoidance strategies for a single population of sage-grouse located in northeastern Nevada.

Stable Isotopes and Ridgway's Rail

Project Lead: Angela Merritt

Little is known regarding the diet of the California Ridgway’s Rail. A 1941 stomach-content analysis completed by a San Francisco Bay naturalist (Moffit) indicated an opportunistic rail diet spanning several trophic levels. No predominant prey items, or a lack of, have been confirmed since. Based on the Moffit work and current location data, most researchers believe that Ridgway's rails forage exclusively in the brackish tidal marsh. A comparison of δ13C, δ15N, δ34S isotope values from clapper rail feathers and an updated gut content analysis is underway to confirm this. The final product will detail the foraging preference for three geographically distinct rail populations, documenting any rails with freshwater isotope signatures. Using museum rail specimens dating back to 1880 will broaden the spatial and temporal scale and ultimately capture diet adaptations in the face of a rising sea level.

 

 

Josh Hull UC Davis
Great Gray Owls in Yosemite

Project Lead: Joseph Medley 

A geographically-isolated population of Great Gray Owls (Strix nebulosa)(GGOW), consisting of approximately 150-200 individuals, is distributed in the central Sierra Nevada, California. Our recent research has documented that this population is genetically unique from other populations in North America. These population genetic results, in conjunction with management concerns regarding impacts of timber harvest, grazing, recreation and water management on GGOWs and their habitat, has generated significant management interest by the Forest Service and other agencies in the development of monitoring methods to track GGOW population status and trends. To date, we have collaborated with the Forest Service to develop and quantitatively-evaluate broadcast and meadow-search methods to document GGOW occupancy based on the presence and detection of owls at survey sites.  However, we also commonly collect molted GGOW feathers when conducting our meadow searches as part of the occupancy surveys. These molted feathers provide a potential source of DNA that can be used to identify individual GGOWs. The objective of our proposed project is to evaluate if the molted feathers can be used to identify individual GGOWs. If individuals can indeed be identified from these molted feather samples, then it becomes possible to use mark-recapture modeling methods to estimate survival and population trend (lambda), and to garner data on dispersal. Thus, it may be possible to develop passive and cost-efficient monitoring designs based on collecting molted feathers at occupied meadow sites, as compared to logistically-difficult and expensive demographic methods (i.e., does not require actual capture and annual resighting of individuals owls). Our goal is to develop scientifically-defensible, effective and cost-efficient monitoring methods and designs that can provide monitoring data on GGOW occupancy, survival, reproduction and population trends to meet the increasing information demands being placed on land managers and regulatory agencies regarding the status of this unique population.

Bay Area Raptor Nesting Survey
 

In collaboration with the Golden Gate Raptor Observatory, we are using data collected during a long-term citizen science project to describe the nest site preferences of Red-shouldered and Red-tailed Hawks nesting in Sonoma and Napa counties.

 

Josh Hull UC Davis
Raptor trend analysis

In collaboration with the Golden Gate Raptor Observatory and the US Forest Service, we are analyzing hawk count data collected in the Marin Headlands to identify population trends in 19 species of migratory raptors.