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P.G.R. Jodice

Publications and source records attributed to P.G.R. Jodice.

9 recordsLinked to original sources
USGS2010

Stress response of brown pelican nestlings to ectoparasite infestation

Measurement of corticosterone has become a useful tool for assessing the response of individuals to ecological stressors of interest. Enhanced corticosterone levels can promote survival of stressful events; however, in situations where a stressor persists and corticosterone levels remain elevated, the adrenocortical response can be detrimental. A potential ecological stressor for wild birds is parasitism by ectoparasites. We studied the stress response of 11-23-day-old brown pelican (Pelecanus occidentalis) nestlings by measuring plasma corticosterone levels in relation to the presence of the soft tick Carios capensis at two colonies in South Carolina in 2005. We expected to see higher baseline and stress-induced levels of corticosterone for parasitized chicks compared to those nestlings with no ticks. Although nestlings mounted a response to capture stress, tick category was not associated with corticosterone levels at either colony. Our results appear to contrast those of previous studies and indicate that the adrenocortical response of the host is likely dependent on the type of ectoparasite and the degree of infestation. ?? 2009 Elsevier Inc.

General and Comparative Endocrinology↗
USGS2007

Longterm trends in nest counts of colonial seabirds in South Carolina, USA

We analyzed temporal and spatial trends in annual nest counts of Brown Pelicans (Pelecanus occidentalis), Royal Terns (Sterna maxima), and Sandwich Terns (Sterna sandvicensis) throughout South Carolina from 1969 through 2005. There was an increase in the number of active pelican nests from 1969 through the mid 1980s, although this was followed by a steady decline that continued through 2005. Numbers of Royal Tern nests have declined during the study period, especially since 1990. In contrast, annual counts of active Sandwich Tern nests remained relatively stable through the mid 1980s, then increased substantially and have since remained stable. During the early years of the study, a greater proportion of nests from each species occurred on colonies within the Cape Romain region, although this distribution appears to have shifted with a greater proportion of nests now occurring along the southern coast. At the statewide level and at each of the primary colonies, we observed a positive correlation in counts of Brown Pelican and Royal Tern nests. Mechanisms underlying the observed trends are unclear. We suggest that priorities for research include (1) determination of diet and foraging locales for all three species, (2) impacts of ectoparasites on condition and survival of pelican chicks, and (3) metapopulation structure of all three species. Management activities should focus primarily on protection of colony sites.

Waterbirds↗
USGS2006

Site-specific effects on productivity of an upper trophic-level marine predator: Bottom-up, top-down, and mismatch effects on reproduction in a colonial seabird

We investigated the relative roles of bottom-up and top-down factors in limiting productivity of an upper trophic level marine predator. Our primary working hypothesis was that the reproductive success of black-legged kittiwakes (Rissa tridactyla) a piscivorous, colonial-nesting seabird, was most limited by the abundance, distribution, and species composition of surface-schooling forage fishes. A secondary working hypothesis was that reproductive loss to kittiwake nest predators was greatest during years of reduced prey availability. We report on a broad-scale, integrated study of kittiwakes and their prey in Prince William Sound, Alaska. Our study spanned five breeding seasons (1995-1999) and focused on three colonies that differed in size (ranging from ca. 220 to ca. 7000 breeding pairs) and proximity to each other (50-135 km apart). Kittiwakes in PWS encountered a variety of aquatic habitats, creating a complex foraging environment for breeding birds. We measured kittiwake reproductive success and foraging activities, while simultaneously measuring the abundance of surface schooling forage fishes throughout the foraging range of breeding kittiwakes. The abundance of primary prey species for kittiwakes (Pacific herring Clupea pallasi, Pacific sand lance Ammodytes hexapterus, and capelin Mallotus villosus) varied both annually and regionally, with no one region consistently having the greatest abundance of prey. Likewise, kittiwake reproductive success varied considerably among colonies and years. We found that bottom-up, top-down, timing mismatch, and colony-specific effects were all important to kittiwake productivity. Although bottom-up effects appeared to be strongest, they were not evident in some cases until other effects, such as geographic location (proximity of colony to prey concentrations) and top-down predation, were considered. Important bottom-up effects on kittiwake reproductive success were not only total prey abundance and distribution, but also species, age composition, and chronology of prey occurrence (match/mismatch of timing with critical brood-rearing periods); these effects varied by colony. Top-down effects of predation on kittiwake nest contents (independent of prey abundance) confounded seabird-forage fish relationships. Ultimately, when confounding factors were minimized, non-linear asymptotic relationships were identified between kittiwakes and their prey, with an asymptotic threshold of fish school surface area density of ca. 5 m2/km2, beyond which top-down, physiological, or phylogenetic constraints likely restrict further reproductive output. The integrated approach of our investigations provided a more thorough understanding of the mechanisms underlying predator-prey relationships in the complex marine environment. However, such mechanistic theories can only be tested and refined through long-term research and monitoring of much greater duration than the 5-year study reported herein. ?? 2006 Elsevier Ltd. All rights reserved.

Progress in Oceanography↗
USGS2006

Daily energy expenditure in free-ranging Gopher Tortoises (Gopherus polyphemus)

Studies of ecological energetics in chelonians are rare. Here, we report the first measurements of daily energy expenditure (DEE) and water influx rates (WIRs) in free-ranging adult Gopher Tortoises (Gopherus polyphemus). We used the doubly labeled water (DLW) method to measure DEE in six adult tortoises during the non-breeding season in south-central Mississippi, USA. Tortoise DEE ranged from 76.7-187.5 kj/day and WIR ranged from 30.6-93.1 ml H2O/day. Daily energy expenditure did not differ between the sexes, but DEE was positively related to body mass. Water influx rates varied with the interaction of sex and body mass. We used a log/log regression model to assess the allometric relationship between DEE and body mass for Gopher Tortoises, Desert Tortoises (Gopherus agassizii), and Box Turtles (Terrapene carolina), the only chelonians for which DEE has been measured. The slope of this allometric model (0.626) was less than that previously calculated for herbivorous reptiles (0.813), suggesting that chelonians may expend energy at a slower rate per unit of body mass compared to other herbivorous reptiles. We used retrospective power analyses and data from the DLW isotope analyses to develop guidelines for sample sizes and duration of measurement intervals, respectively, for larger-scale energetic studies in this species. ?? 2006 by the American Society of Ichthyologists and Herpetologists.

Copeia↗
USGS2006

Increased energy expenditure by a seabird in response to higher food abundance

Variability in forage fish abundance strongly affects seabird behavior and reproductive success, although details of this relationship are unclear. During 1997 and 1998, we measured (1) daily energy expenditure (DEE) of 80 parent black-legged kittiwakes Rissa tridactyla at 2 colonies in Prince William Sound, Alaska (North Icy Bay and Shoup Bay), (2) abundance of surface-schooling forage fishes within the foraging range of each colony, and (3) diet composition, energy delivery rates to nestlings, and reproductive success of kittiwakes at these same colonies. Female DEE was highest at North Icy Bay in 1998, while male DEE did not differ by colony year. Abundances of Pacific herring Clupea pallasi and sand lance Ammodytes hexapterus were highest near North Icy Bay in 1998 and nearly egual in density, although Age 1+ herring comprised the majority of the diet there. Energy delivery rates to nestlings, nestling growth rates, and productivity were also highest at North Icy Bay in 1998. We suggest that female kittiwakes responded to the increased abundance of Age 1+ herring near North Icy Bay in 1998 by increasing their DEE, which in turn positively affected reproductive success. Given that adult kittiwakes have been shown to suffer decreased survival as a response to increased energy expenditure during brood rearing, the positive correlation we observed between increased abundance of a high quality food source, parental effort, and productivity is consistent with maximizing lifetime reproductive success. The lack of a response in male DEE suggests that brood-rearing roles in kittiwakes differ between genders. ?? Inter-Research 2006.

Marine Ecology Progress Series↗
USGS2005

Reddish Egret extends its breeding range along the North American Atlantic coast into South Carolina

We report the northernmost breeding record of the Reddish Egret (Egretta rufescens) along the North American Atlantic Coast. Nesting activity was first seen in late May 2004, and on 6 July 2004 a nest was discovered with two young chicks on Marsh Island, a barrier island located within Cape Romain National Wildlife Refuge, South Carolina, USA. Reddish Egret nestlings were last observed within 1 m of the nest on 30 July 2004. This represents a northward extension of ca. 450 km in the breeding range of this species and, for the U.S. Atlantic Coast, the only recorded instance of nesting north of Florida.

Waterbirds↗
USGS2003

Variation in energy expenditure among black-legged kittiwakes: Effects of activity-specific metabolic rates and activity budgets

We sought to determine the effect of variation in time-activity budgets (TABs) and foraging behavior on energy expenditure rates of parent black-legged kittiwakes (Rissa tridactyla). We quantified TABs using direct observations of radio-tagged adults and simultaneously measured field metabolic rates (FMR) of these same individuals (n = 20) using the doubly labeled water technique. Estimated metabolic rates of kittiwakes attending their brood at the nest or loafing near the colony were similar (ca. 1.3 x basal metabolic rate [BMR]), although loafing during foraging trips was more costly (2.9 x BMR). Metabolic rates during commuting flight (7.3 x BMR) and prey-searching flight (6.2 x BMR) were similar, while metabolic rates during plunge diving were much higher (ca. 47 x BMR). The proportion of the measurement interval spent foraging had a positive effect on FMR (R2 = 0.68), while the combined proportion of time engaged in nest attendance and loafing near the colony had a negative effect on FMR (R2 = 0.72). Thus, more than two-thirds of the variation in kittiwake FMR could be explained by the allocation of time among various activities. The high energetic cost of plunge diving relative to straight flight and searching flight suggests that kittiwakes can optimize their foraging strategy under conditions of low food availability by commuting long distances to feed in areas where gross foraging efficiency is high.

Physiological and Biochemical Zoology↗
USGS2000

Sexing adult black-legged kittiwakes by DNA, behavior, and morphology

We sexed adult Black-legged Kittiwakes ( Rissa tridactyla ) using DNA-based genetic techniques, behavior and morphology and compared results from these techniques. Genetic and morphology data were collected on 605 breeding kittiwakes and sex-specific behaviors were recorded for a sub-sample of 285 of these individuals. We compared sex classification based on both genetic and behavioral techniques for this sub-sample to assess the accuracy of the genetic technique. DNA-based techniques correctly sexed 97.2% and sex-specific behaviors, 96.5% of this sub-sample. We used the corrected genetic classifications from this sub-sample and the genetic classifications for the remaining birds, under the assumption they were correct, to develop predictive morphometric discriminant function models for all 605 birds. These models accurately predicted the sex of 73-96% of individuals examined, depending on the sample of birds used and the characters included. The most accurate single measurement for determining sex was length of head plus bill, which correctly classified 88% of individuals tested. When both members of a pair were measured, classification levels improved and approached the accuracy of both behavioral observations and genetic analyses. Morphometric techniques were only slightly less accurate than genetic techniques but were easier to implement in the field and less costly. Behavioral observations, while highly accurate, required that birds be easily observable during the breeding season and that birds be identifiable. As such, sex-specific behaviors may best be applied as a confirmation of sex for previously marked birds. All three techniques thus have the potential to be highly accurate, and the selection of one or more will depend on the circumstances of any particular field study.

Alaska↗