The Experts below are selected from a list of 72 Experts worldwide ranked by ideXlab platform
Bruce H. Pugesek - One of the best experts on this subject based on the ideXlab platform.
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mark resighting analysis of a California Gull population
Journal of Applied Statistics, 1995Co-Authors: Bruce H. Pugesek, Chris Nations, Kenneth L Diem, Roger PradelAbstract:California Gulls ( Larus californicus ) of known age and sex were censused on their breeding colony in 1979, 1980 and 1984 through 1993. Ages of 235 males and 196 females ranged from 4 to 27 years. Age classes used in the analysis were limited to 17, 4 through 19, and 20 or more as a final age category because data on Gulls over 20 were sparse. Survival declined with age in a way that was parsimoniously modelled with a quadratic function. Other factors, sex and time, did not explain any variation in survival. Resighting depended on age, sex and time. Younger adults skipped breeding more frequently than did older adults, and females skipped breeding more frequently than did males. There was also good evidence for time dependence in resighting probability, but its inclusion in the model occurred at the expense of interpretability and precision. In a data set such as this, resighting probability may assume more importance than a mere 'nuisance parameter'. In this study, resighting history measured attendance...
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Offspring growth in the California Gull: reproductive effort and parental experience hypotheses
Animal Behaviour, 1995Co-Authors: Bruce H. PugesekAbstract:Abstract Measures of adult feeding and foraging behaviour in the California Gull, Larus californicus , were related to the growth of their offspring. Offspring showed significantly higher growth when average feeding interval, a measure of the time interval between feedings, and feeding latency following foraging decreased. The amount of time parents foraged was positively related to offspring growth and negatively correlated with average feeding interval. Either (1) increased foraging efficiency with parental age, or (2) increased reproductive effort with age, could explain age-related differences in patterns of feeding behaviour and their impact on offspring growth. However, data on foraging time support only the hypothesis of increased reproductive effort with parental age.
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Alternate reproductive strategies in the California Gull
Evolutionary Ecology, 1992Co-Authors: Bruce H. Pugesek, P. WoodAbstract:We analysed 6 years of reproduction data for 176 California Gulls ( Larus californicus ) surviving from 1980 to 1988. Using a statistical model adapted from Rao's (1958) and Tucker's (1966) generalized growth curve analysis, we reconstructed the reproductive patterns of Gulls aged from 0 to 26 years. Individuals were highly consistent in following one of two patterns of reproduction. In a primary pattern employed by most Gulls, individuals skipped breeding less frequently and laid larger clutches as they aged. Clutch size increased to a plateau and remained at high levels throughout remaining life. In an alternate pattern employed by a smaller subset of the sample, clutch size also increased to a plateau. However, as a result of frequent skipping of breeding and smaller clutches, this plateau was considerably lower compared to that of Gulls adopting the primary reproductive pattern. Data on fledging success from 1980 and 1984 were consistent with the finding of two reproductive patterns. Gulls adopting the alternate reproductive pattern produce fewer offspring per breeding attempt but survive longer than Gulls adopting the primary pattern. The frequency of Gulls employing the alternate pattern will increase with age relative to Gulls employing the primary pattern. The alternate pattern, and not senescence, may explain why several cross-sectional studies on seabirds report declines among the oldest breeders in measures of clutch size, egg mass, hatching success, and fledging success.
Joshua T Ackerman - One of the best experts on this subject based on the ideXlab platform.
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California Gull larus californicus space use and timing of movements in relation to landfills and breeding colonies
Waterbirds, 2018Co-Authors: Joshua T Ackerman, Sarah H Peterson, Danika C Tsao, John Y TakekawaAbstract:Expanding Gull (Laridae) populations throughout the world have been attributed to the availability of anthropogenic food subsidies. The influence of landfills on California Gull (Larus californicus) space use and the timing of their movements was evaluated in San Francisco Bay, California, USA. Using radio telemetry, 108 California Gulls were tracked, > 7,000 locations were recorded, and > 1 million detections were obtained at automated logger systems placed at the two main landfills and three major breeding colonies. Population home range (31-35 km2) and core use areas (2-3 km2) overlapped landfills and colonies, and expanded after breeding. California Gull attendance at landfills (1.6-19.0 km from colonies) increased throughout breeding and post-breeding, whereas attendance at colonies was low during pre-breeding (20%-40% per day), increased during breeding (60%-80% per day), and declined into and during post-breeding (< 20% per day). California Gull attendance at landfills was greatest when garbage was delivered from 06:00 hr in the morning until 18:00 hr at night. In contrast, California Gull attendance at colonies during breeding was greater at night from 20:00 hr to 05:00 hr (50%-70% per hr) than during the day from 06:00 hr to 18:00 hr (30%-40% per hr). Landfills played a predominant role in California Gull space use and the timing of their movements in this highly urbanized estuary.
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California Gull chicks raised near colony edges have elevated stress levels
General and Comparative Endocrinology, 2011Co-Authors: Garth Herring, Joshua T AckermanAbstract:Coloniality in nesting birds represents an important life history strategy for maximizing reproductive success. Birds nesting near the edge of colonies tend to have lower reproductive success than individuals nesting near colony centers, and offspring of edge-nesting parents may be impaired relative to those of central-nesting parents. We used fecal corticosterone metabolites in California Gull chicks (Larus californicus) to examine whether colony size or location within the colony influenced a chick’s physiological condition. We found that chicks being raised near colony edges had higher fecal corticosterone metabolite concentrations than chicks raised near colony centers, but that colony size (ranging from 150 to 11,554 nests) had no influence on fecal corticosterone levels. Fecal corticosterone metabolite concentrations also increased with chick age. Our results suggest that similarly aged California Gull chicks raised near colony edges may be more physiologically stressed, as indicated by corticosterone metabolites, than chicks raised near colony centers.
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sexing California Gulls using morphometrics and discriminant function analysis
Waterbirds, 2010Co-Authors: Garth Herring, Joshua T Ackerman, Collin A Eaglessmith, John Y TakekawaAbstract:Abstract. A discriminant function analysis (DFA) model was developed with DNA sex verification so that external morphology could be used to sex 203 adult California Gulls (Larus californicus) in San Francisco Bay (SFB). The best model was 97% accurate and included head-to-bill length, culmen depth at the gonys, and wing length. Using an iterative process, the model was simplified to a single measurement (head-to-bill length) that still assigned sex correctly 94% of the time. A previous California Gull sex determination model developed for a population in Wyoming was then assessed by fitting SFB California Gull measurement data to the Wyoming model; this new model failed to converge on the same measurements as those originally used by the Wyoming model. Results from the SFB discriminant function model were compared to the Wyoming model results (by using SFB data with the Wyoming model); the SFB model was 7% more accurate for SFB California Gulls. The simplified DFA model (head-to-bill length only) provided...
P. Wood - One of the best experts on this subject based on the ideXlab platform.
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Alternate reproductive strategies in the California Gull
Evolutionary Ecology, 1992Co-Authors: Bruce H. Pugesek, P. WoodAbstract:We analysed 6 years of reproduction data for 176 California Gulls ( Larus californicus ) surviving from 1980 to 1988. Using a statistical model adapted from Rao's (1958) and Tucker's (1966) generalized growth curve analysis, we reconstructed the reproductive patterns of Gulls aged from 0 to 26 years. Individuals were highly consistent in following one of two patterns of reproduction. In a primary pattern employed by most Gulls, individuals skipped breeding less frequently and laid larger clutches as they aged. Clutch size increased to a plateau and remained at high levels throughout remaining life. In an alternate pattern employed by a smaller subset of the sample, clutch size also increased to a plateau. However, as a result of frequent skipping of breeding and smaller clutches, this plateau was considerably lower compared to that of Gulls adopting the primary reproductive pattern. Data on fledging success from 1980 and 1984 were consistent with the finding of two reproductive patterns. Gulls adopting the alternate reproductive pattern produce fewer offspring per breeding attempt but survive longer than Gulls adopting the primary pattern. The frequency of Gulls employing the alternate pattern will increase with age relative to Gulls employing the primary pattern. The alternate pattern, and not senescence, may explain why several cross-sectional studies on seabirds report declines among the oldest breeders in measures of clutch size, egg mass, hatching success, and fledging success.
Nicholas J Ashbolt - One of the best experts on this subject based on the ideXlab platform.
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molecular detection of campylobacter spp in California Gull larus californicus excreta
Applied and Environmental Microbiology, 2011Co-Authors: Hodon Ryu, Jorge Santo W Domingo, John F Griffith, Nicholas J AshboltAbstract:We examined the prevalence, quantity, and diversity of Campylobacter species in the excreta of 159 California Gull (Larus californicus) samples using culture-, PCR-, and quantitative PCR (qPCR)-based detection assays. Campylobacter prevalence and abundance were relatively high in the Gull excreta examined; however, C. jejuni and C. lari were detected in fewer than 2% of the isolates and DNA extracts from the fecal samples that tested positive. Moreover, molecular and sequencing data indicated that most L. californicus campylobacters were novel (<97% 16S rRNA gene sequence identity to known Campylobacter species) and not closely related to species commonly associated with human illness. Campylobacter estimates were positively related with those of fecal indicators, including a Gull fecal marker based on the Catellicoccus marimammalium 16S rRNA gene.
Robert J Letcher - One of the best experts on this subject based on the ideXlab platform.
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volatile methylsiloxanes and organophosphate esters in the eggs of european starlings sturnus vulgaris and congeneric Gull species from locations across canada
Environmental Science & Technology, 2017Co-Authors: Zhe Z Lu, Pamela A Martin, Neil M N M Burgess, Louise Champoux, John E Elliott, Enzo E Baressi, Amila O De Silva, Shane R De Solla, Robert J LetcherAbstract:Volatile methylsiloxanes (VMSs) and organophosphate esters (OPEs) are two suites of chemicals that are of environmental concern as organic contaminants, but little is known about the exposure of wildlife to these contaminants, particularly in birds, in terrestrial and aquatic ecosystems. The present study investigates the spatial distributions of nine cyclic and linear VMSs and 17 OPEs in the eggs of European starlings (Sturnus vulgaris) and three congeneric Gull species (i.e., herring Gull (Larus argentatus), glaucous-winged Gull (L. glaucescens), and California Gull (L. californicus)) from nesting sites across Canada. ∑VMS concentrations for all bird eggs were dominated by decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), and octamethylcyclotetrasiloxane (D4). With European starlings, birds breeding adjacent to landfill sites had eggs containing significantly greater ∑VMS concentrations (median: 178 ng g–1 wet weight (ww)) compared with those from the urban industrial (20 ng g–1 ww)...
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Volatile Methylsiloxanes and Organophosphate Esters in the Eggs of European Starlings (Sturnus vulgaris) and Congeneric Gull Species from Locations across Canada
2017Co-Authors: Pamela A Martin, Neil M N M Burgess, Louise Champoux, John E Elliott, Enzo E Baressi, Amila O De Silva, Shane R De Solla, Robert J LetcherAbstract:Volatile methylsiloxanes (VMSs) and organophosphate esters (OPEs) are two suites of chemicals that are of environmental concern as organic contaminants, but little is known about the exposure of wildlife to these contaminants, particularly in birds, in terrestrial and aquatic ecosystems. The present study investigates the spatial distributions of nine cyclic and linear VMSs and 17 OPEs in the eggs of European starlings (Sturnus vulgaris) and three congeneric Gull species (i.e., herring Gull (Larus argentatus), glaucous-winged Gull (L. glaucescens), and California Gull (L. californicus)) from nesting sites across Canada. ∑VMS concentrations for all bird eggs were dominated by decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), and octamethylcyclotetrasiloxane (D4). With European starlings, birds breeding adjacent to landfill sites had eggs containing significantly greater ∑VMS concentrations (median: 178 ng g–1 wet weight (ww)) compared with those from the urban industrial (20 ng g–1 ww) and rural sites (1.3 ng g–1 ww), indicating that the landfills are important sources of VMSs to Canadian terrestrial environments. In Gull eggs, the median ∑VMS concentrations were up to 254 ng g–1 ww and suggested greater detection frequencies and levels of VMSs in aquatic- versus terrestrial-feeding birds in Canada. In contrast, the detection frequency of OPEs in all European starling and Gull eggs was lower than 16%. This suggested that low dietary exposure or rapid metabolism of accumulated OPEs occurs in aquatic feeding birds and may warrant further investigation for the elucidation of the reasons for these differences
