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Wallace S.J.,Queens University | Wolf S.G.,Center for Biological Diversity | Bradley R.W.,Point Blue Conservation Science formerly PRBO | Harvey A.L.,California Institute of Environmental Studies | Friesen V.L.,Queens University
Journal of Biogeography | Year: 2015

Aim: Our aim was to investigate the influence of biogeographical barriers along the Pacific coast of North America on population genetic structure and gene flow using Cassin's auklet (Ptychoramphus aleuticus) as a test case. Location: We collected samples from 287 Cassin's auklets breeding along the Pacific coast of North America from the Aleutian Islands, Alaska, USA, to Baja California, Mexico. Methods: We amplified a 706 base pair fragment of the mitochondrial control region and 11 microsatellites to obtain independent estimates of population genetic structure and gene flow among colonies using programs based on coalescent and Bayesian theory. We tested whether genetic differentiation was related to geographical distance between sampling sites, and whether gene flow has occurred between differentiated groups. Results: We found two distinct genetic groups along the Cassin's auklet breeding range. These clusters matched the current subspecies designations, except that individuals breeding in the Channel Islands, California, were traditionally classified with the northern subspecies but were more genetically similar to the Baja California subspecies. Population genetic differentiation was not evident within either of the two genetic groups, despite large geographical distances between sampling locations. Evidence suggests that gene flow has occurred from the northern genetic group (Aleutian Islands to Southeast Farallon Islands) into the southern genetic group (Channel Islands to San Benito Island) since divergence, but gene flow may not have occurred in the opposite direction. These results suggest that a barrier to gene flow from south to north may occur at Point Conception. Main conclusions: Although a relatively short geographical distance occurs between sampling sites of Cassin's auklets across Point Conception, individuals breeding north of Point Conception are genetically differentiated from individuals breeding in southern California and Baja California. Population genetic differentiation of the southern genetic group provides support for a role of a barrier to gene flow around Point Conception in generating biodiversity in this area. © 2015 John Wiley & Sons Ltd.

Robison K.M.,University of California at Davis | Robison K.M.,Colibri Ecological Consulting LLC | Anderson D.W.,University of California at Davis | Anderson D.W.,California Institute of Environmental Studies | And 2 more authors.
Waterbirds | Year: 2015

Western (Aechmophorus occidentalis) and Clark's (A. clarkii) grebes are long-lived, migratory waterbirds that are sensitive to human-caused disturbance while nesting. Sampling the age distribution of post-hatch chicks provides a method for estimating the timing of nest initiation without causing disturbance to breeding colonies. The goals of this work were to describe trends in breeding productivity at two of the largest nesting colonies in northern California and illustrate how brood size can be used to evaluate nesting phenology in Aechmophorus grebes. No differences were found in brood size between species. Brood size decreased linearly as nest initiation date increased, showing no differences in the rate of decline among age classes of young. Within seasons, older broods were found to be significantly smaller than younger broods, suggesting that mortality was occurring after hatching thereby reducing the potential number of chicks recruited into the adult population.

Adams J.,U.S. Geological Survey | Carter H.R.,Humboldt State University | McChesney G.J.,Humboldt State University | McChesney G.J.,U.S. Fish and Wildlife Service | And 2 more authors.
Marine Ornithology | Year: 2016

We mist-netted and examined Leach’s Storm-Petrels Oceanodroma leucorhoa (LESP) caught during 1991-2015 at three locations in the California Channel Islands (CCI): Prince Island, Santa Barbara-Sutil islands and Scorpion Rock. Although mist-netting methods and effort varied between two study periods (1991-1995, 2004-2007 and 2015), during 750 h effort we captured 41 LESP during April-August, with two of these recaptured after initial banding. The majority (78%) were classified as likely breeders based on a well-developed incubation patch. We summarize island-specific efforts, capture rates and morphological measurements made at these three CCI locations. Captured LESP displayed a multimodal distribution in the overall degree of white rump plumage, with 28% classified as mostly “dark-rumped.” The majority of LESP (72%) captured in the CCI have variable white rumps, similar to what has been reported for northern California and the Farallon Islands. However, the relative proportions of “dark-rumped” individuals captured in the northern CCI is intermediate, within the shift starting at the Farallon Islands and increasing in prevalence toward the San Benito Islands, Baja California. More remains to be learned about LESP in the CCI, for which additional mist-netting efforts are needed, using a standardized approach that targets LESP. © 2016, Marine Ornithology. All rights reserved.

Harvey A.L.,Channel Islands National Park | Mazurkiewicz D.M.,Sutil Conservation Ecology | McKown M.W.,Conservation Metrics Inc. | Barnes K.W.,Sutil Conservation Ecology | And 2 more authors.
Marine Ornithology | Year: 2016

Ashy Storm-Petrels (ASSP) breed in a range restricted to the southern California Current, from Mendocino County in northern California, United States, to the Coronado Islands in northwest Baja California, Mexico. Approximately half the global population nests on the California Channel Islands, but nesting at one of them, Anacapa Island, had not been recorded before this study. In 2011, 10 years af ter rats were eradicated, we conducted a study to determine the breeding status of ASSP on Anacapa Island. We used habitat searches coupled with acoustic sensors to assess potential nesting areas and conducted mist netting to determine general presence. We found one active nest containing a nearly fledged ASSP chick in 2011, representing the first breeding record for the island. © 2016, Marine Ornithology. All rights reserved.

Anderson D.W.,University of California at Davis | Anderson D.W.,California Institute of Environmental Studies | Henny C.J.,U.S. Geological Survey | Godinez-Reyes C.,CONANP SEMARNAT | And 5 more authors.
Marine Ornithology | Year: 2014

In 2009, the Brown Pelican Pelecanus occidentalis was removed from the US Endangered Species List. The California subspecies P. o. californicus (hereafter CABRPE) was also removed from the California state endangered species list. Three years earlier (2006), we estimated the metapopulation of CABRPE to be 70 680 ± 2 640 breeding pairs (mean ± SD) and 195 900 ± 7 225 individuals. The largest single breeding aggregation within the range occurred among two to three islands of the San Lorenzo Archipelago, Gulf of California (GOC), totaling ~17 225 breeding pairs, or ~24.4% of the metapopulation. This and the other 4 subpopulations were composed of a single "core" breeding aggregation (on one or a few adjacent islands) and many smaller but isolated colonies (a colony represents all birds on a single island). Extremely small colonies (<65 nests) made up ~35.6% of total colonies, but only ~ 0.9% of the total estimated numbers, corrected for detectability. Modal colony size throughout the range was much smaller (230 to 1 300 breeding pairs), indicating that small, scattered colonies and sub-colonies have a function in CABRPE distributional dynamics and demography. Thus, negative single-survey data (no occupancy and small numbers) still have conservation importance as alternate or growing colonies in source-sink dynamics. Little numerical change in CABRPE in at least three decades was indicated from less precise data south of the northernmost Southern California Bight (SCB) subpopulation, but significant recent improvements in the SCB were reflected by our high estimates in 2006, supporting the USFWS delisting. At that time, we estimated the improved SCB breeding population as 11 695 ± 450 pairs. However, continuing threats throughout the range, especially in the south, now include commercial fishing, tourist developments, increased human activities, and extensive/expanding aqua-cultural developments (as well as, to a lesser degree, agricultural activities). Repeated endangerment is a possibility. Continued monitoring will be important.

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