Brian E. Washburn

USING FECAL GLUCOCORTICOIDS FOR STRESS ASSESSMENT IN MOURNING DOVES

Abstract Fecal glucocorticoid assays provide a potentially useful, noninvasive means to study physiological responses of wildlife to various stressors. The objective of our study was to validate a method for measuring glucocorticoid metabolites in Mourning Dove (Zenaida macroura) feces. We validated the assay using standard procedures (e.g., parallelism, recovery of exogenous corticosterone) to demonstrate that the assay accurately and precisely measured glucocorticoid metabolites in Mourning Dove fecal extracts. We conducted adrenocorticotropin (ACTH) challenge experiments to validate the assays ability to determine biologically important changes in fecal glucocorticoids. Fecal glucocorticoid levels increased significantly approximately 2–3 hr after administration of ACTH at 50 IU per kg body mass to wild Mourning Doves held in captivity. In contrast, fecal glucocorticoid metabolites did not increase in control birds, birds that received saline injections, or a lower dose of ACTH (1 IU per kg body mass). Variation in overall fecal glucocorticoid metabolite levels may have been influenced by season and the length of time birds were held in captivity. Noninvasive fecal glucocorticoid metabolite analyses, in combination with demographic information, may have considerable utility for monitoring the effects of natural and anthropogenic disturbances on Mourning Dove populations. Uso de Glucocorticoides Fecales Para Evaluar el Estrés en Zenaida macroura Resumen. Las evaluaciones de glucocorticoides fecales representan un medio no invasor potencialmente útil para estudiar las respuestas fisiológicas de los animales silvestres ante agentes causantes de estrés. El objetivo de nuestro estudio fue validar un método para medir metabolitos glucocorticoides en heces de palomas Zenaida macroura. Validamos el método mediante procedimientos estándar (e.g., paralelismo, recuperación de corticosterona exógena) para demostrar que éste mide con exactitud y precisión los metabolitos glucocorticoides en extractos fecales de Z. macroura. Realizamos experimentos de desafío con adrenocorticotropina (ACTH) para validar la habilidad que tenía el método para determinar cambios biológicamente importantes en los glucocorticoides fecales. Los niveles de glucocorticoides fecales aumentaron de forma significativa aproximadamente 2–3 hr después de la administración de ACTH a 50 IU por kg de peso corporal a palomas silvestres mantenidas en cautiverio. En contraste, los metabolitos glucocorticoides fecales no aumentaron en aves control, ni en aves que recibieron inyecciones salinas o una menor dosis de ACTH (1 IU por kg de peso corporal). La variación en los niveles generales de metabolitos glucocorticoides fecales podría haber sido influenciada por la estación y la longitud del período de tiempo en que las aves fueron mantenidas en cautiverio. Los análisis no invasores de metabolitos glucocorticoides, en combinación con información demográfica, podrían ser de considerable utilidad para monitorear los efectos de los disturbios naturales y antropogénicos sobre las poblaciones de Z. macroura.

USING A COMMERCIALLY AVAILABLE ENZYME IMMUNOASSAY TO QUANTIFY TESTOSTERONE IN AVIAN PLASMA

Abstract ABSTRACT Using a commercially available testosterone enzyme immunoassay (EIA), we developed and validated an assay procedure for determining testosterone levels in small-volume (20 µL) avian plasma samples. We evaluated this EIAs utility by measuring plasma testosterone levels in Mourning Doves (Zenaida macroura), White-eyed Vireos (Vireo griseus), Red-eyed Vireos (Vireo olivaceus), and Indigo Buntings (Passerina cyanea). Standard biochemical validations (e.g., parallelism, recovery of exogenous testosterone) demonstrated that the assay accurately and precisely measured testosterone in avian plasma. We compared plasma testosterone levels in males and females of all four species and Indigo Buntings in various reproductive stages to physiologically validate the assays ability to determine biologically important changes in testosterone levels. Plasma testosterone levels were higher in males compared to females in three of four species. Prebreeding and breeding male Indigo Buntings had higher circulating testosterone levels than postbreeding males. Testosterone levels in our study were similar to reported values for other passerine species using radioimmunoassay procedures. Our results suggest that this EIA procedure is very effective for determining testosterone levels in small-volume avian plasma samples and is sensitive enough to detect biologically important changes in the gonadal activity of birds. Thus, this assay has considerable utility for measuring testosterone in small birds (<15 g), from which only small volumes of plasma (20 µL) can be collected.

Wildlife Responses to Vegetation Height Management in Cool-season Grasslands

Abstract Herbaceous vegetation comprises the main habitat type in cool-seasons grasslands and can be managed by various methods. We compared changes in plant communities and bird and mammal use of grasslands that were not managed, managed by mechanical methods (mowing), or managed by chemical methods (plant growth regulator). This 1-year study was conducted from May through October 2003 in Erie County, Ohio. Twelve circular 1.5 ha plots were established: 4 were not managed, 4 were mowed to maintain vegetation height between 9–15 cm, and 4 were sprayed with a plant growth regulator and mowed when vegetation exceeded 15 cm. We monitored vegetation growth, measured plant community composition, and observed all plots for wildlife activity each week. Vegetation in unmanaged plots was taller and denser (P < 0.001) than vegetation in mowed and growth regulator plots. Plant community characteristics differed among study plots (P < 0.001); managed plots had higher grass cover and lower woody cover than unmanaged plots. We observed more (P < 0.001) total birds per 5-minute survey in unmanaged than mowed or growth regulator plots. We observed more (P < 0.001) white-tailed deer (Odocoileus virginianus) in mowed plots than either control or growth regulator plots. We captured 13 small mammals in unmanaged plots and no small mammals in managed plots. Applying the plant growth regulator was not a cost-effective alternative to mowing for managing vegetation height in our study. Vegetation height management practices altered plant communities and animal use of grassland areas and thus might be useful for accomplishing species-specific habitat management objectives.

Effects of radiotransmitters on fecal glucocorticoid metabolite levels of three-toed box turtles in captivity

Abstract The increased use of radiotelemetry for studying movement, resource selection, and population demographics in reptiles necessitates closer examination of the assumption that radiotransmitter attachment does not bias study results. We determined the effects of radiotransmitter attachment on fecal glucocorticoid metabolite levels of wild three-toed box turtles (Terrapene carolina triunguis) in captivity. During May 2002 we captured 11 adult three-toed box turtles in central Missouri. We housed turtles in individual pens in a semi-natural outdoor setting. We radiotagged 6 turtles, and the remaining 5 turtles served as controls. We captured and handled all turtles similarly during treatments. We collected feces daily prior to attachment (14 June–05 July 2002), while transmitters were attached (06 July–02 August 2002), and after transmitters were removed (03 August–24 August 2002). We conducted a standard assay validation and found that the assay accurately and precisely quantified fecal glucocorticoid metabolites of box turtles. We did not find a significant effect of radiotransmitter attachment on fecal glucocorticoid metabolite levels of three-toed box turtles (F1,9 =0.404, P = 0.541). Fecal glucocorticoid metabolite levels of control and treatment turtles increased significantly during the study (F2,166 =7.874, P = 0.001), but there was no treatment:period interaction (F2, 166 = 0.856, P = 0.427). Additionally, we did not find a significant relationship between glucocorticoid metabolite levels and time in captivity (r2 = 0.01, F1,179 = 2.89, P = 0.091) or maximum daily temperature (r2<0.01, F1,179 = 0.301, P = 0.584). Our results suggested that radiotransmitter attachment did not significantly increase fecal glucocorticoid metabolite levels in adult three-toed box turtles; however, we conducted our study in captivity and sample sizes were small. Thus, more research is needed to assess potential effects of radiotransmitters on turtles in the wild. We believe this study is the first to validate the use of fecal glucocorticoid metabolite measures for reptiles, which might prove useful in other research studies.

Validation of Fecal Glucocorticoid Metabolite Assays for South African Herbivores

Abstract Fecal glucocorticoid metabolite (FGM) assays are a popular means of monitoring adrenocortical activity (i.e., physiological stress response) in wildlife. Species-specific differences in glucocorticoid metabolism and excretion require assay validation, including both laboratory and biological components, before assay use in new species. We validated a commercially available radioimmunoassay (MP 125I corticosterone RIA kit [MP Biomedicals, Solon, OH]) for measuring FGMs of several South African herbivores, including giraffe (Giraffa camelopardalis), impala (Aepyceros melampus), nyala (Tragelaphus buxtoni), kudu (Tragelaphus strepsiceros), wildebeest (Connochaetes taurinus), and zebra (Equus burchelli). These herbivores are important in South African parks and reserves for ecotourism and as a prey base for predators and serve an integral role in ecosystem processes. Standard biochemical validations (e.g., recovery of exogenous corticosterone, intra- and interassay variation, and parallelism) demonstrated that the assay accurately and precisely measured FGMs of all 6 herbivore species. Our biological validations demonstrated that the assay was sensitive enough to detect changes in FGM production associated with season. Samples collected during the dry season (Jun–Aug) contained higher FGM concentrations than those from the wet season (Dec–Feb) in all species. We established optimal sample dilutions and reference FGM levels for these 6 herbivores, which can now be used to monitor the effects of management and ecotourism activities on the stress responses of these herbivores.

RELATIONSHIPS AMONG FECAL LUNGWORM LOADS, FECAL GLUCOCORTICOID METABOLITES, AND LAMB RECRUITMENT IN FREE-RANGING ROCKY MOUNTAIN BIGHORN SHEEP

Most wild Rocky Mountain big-horn sheep (Ovis canadensis canadensis) in northern latitudes are infected with lungworms. Indirect effects of lungworms on bighorn sheep are unknown, but high pulmonary burdens might increase stress (i.e., elevated glucocorticoid levels), and chronic stress could in turn decrease fitness. We hypothesized that high lungworm burdens in Rocky Mountain bighorn ewes increase stress, thereby increasing lamb mortality. To test our hypothesis, one subherd of bighorn sheep in Custer State Park, South Dakota was provided a free-choice loose mineral mix containing the anthelmintic fenbendazole every six weeks from March 1999 to August 2000 to eliminate lungworms; another subherd served as the control. Daily, individually marked ewes were located telemetrically from the ground and uniquely marked animals were observed until they defecated. After the herd moved from the area, fecal samples were collected and stored at −23 C. A consistent number of samples per season per herd (x̄=16.56±3.99 samples) were collected. =Fecal larval lungworm levels (LPG) in the treatment subherd were lower than levels in the control subherd; however, there was no difference in fecal glucocorticoid metabolite (FGM) levels between the two subherds. Fecal glucocorticoid metabolite levels varied by season in both subherds, with levels in winter lower than during the other three seasons. Lamb:ewe ratios were not different between the control and treatment subherds at the end of summer 1999. In contrast, the treatment group had a lower lamb:ewe ratio at the end of summer 2000 despite having lower LPG. However, this result was attributed to lower ewe production, not lower lamb survival. The LPG levels were not correlated with FGM concentrations; instead, FGM levels might reflect normal seasonal patterns. Other factors, including contagious ecthyma, were more important for determining lamb mortality than LPG and FGM levels during our study. We suggest further experimental work over a longer duration to address these relationships.

Physiological effects of radiotransmitters on mourning doves

Abstract It is critical to understand how radiotransmitters and their attachment techniques impact marked individuals. Many studies of transmitter effects assess only overt, deleterious effects. However, physiological effects caused by attachment techniques might compromise the integrity of resulting information. Our objectives, therefore, were to assess the efficacy of subcutaneous implants and determine the physiological effects on mourning doves (Zenaida macroura) using heterophil: lymphocyte (H:L) ratios, and fecal glucocorticoid measures. We conducted 2 trials with 60 mourning doves; 1 in summer-autumn (trial #1) and 1 in autumn-winter (trial #2). For each trial we assigned 15 male and 15 female doves to either a subcutaneous implant treatment or a control group. During the 2 trials, we observed no differences in body masses, H:L ratios or fecal corticosterone levels between mourning doves with subcutaneous implants and the control group. Given the ultimate use of the information obtained from telemetry projects and cost of the resulting initiatives, expenditures associated with rigorous experimental evaluations can only improve the basis of reliable knowledge used in making resource management decisions

Arthropods of a semi-natural grassland in an urban environment: the John F. Kennedy International Airport, New York

Semi-natural grassland habitat fragments, such as those found on airports, might be important for arthropod conservation and biodiversity in urban ecosystems. The objectives of this study were to: (1) describe the arthropod communities present within the grasslands on the John F. Kennedy International Airport and (2) assess spatial and temporal variation in those arthropod communities. We collected arthropods using a vacuum sampler during 2003 and using sweep-net collection methods during 2003 and 2004. During 2003, a total of 1,467 arthropods, representing 17 orders and 68 families were found in vacuum samples. A total of 3,784 arthropods, representing 12 orders and 94 families were collected in sweep-net samples during 2003. In 2004, a total of 3,281 arthropods, representing 12 orders and 85 families were collected in sweep-net samples. Hemiptera, Orthoptera, and Diptera were the most abundant taxa, accounting for 47, 18, and 14% of all arthropods captured, respectively. We found evidence of spatial and temporal variation in arthropod abundance, in particular as noted by fluctuations in Orthoptera: Acrididae and Hemiptera: Auchenorrhyncha. Hemipteran family diversity was also influenced by habitat type. Grassland habitats on airfields, although influenced by anthropogenic factors (e.g., mowing), have the potential to provide abundant and diverse arthropod communities and might serve as a refugium for such species within urban ecosystems.

THE SPRING MIGRATION OF ADULT NORTH AMERICAN OSPREYS

Abstract Most North American Ospreys (Pandion haliaetus) are migratory, breeding in northern latitudes and migrating long distances to and from their wintering grounds in the tropics. Although fall migration patterns of North American Ospreys have been described and studied, very little has been published about the spring migration of these birds. We used satellite telemetry to: (1) determine the characteristics (timing, duration, migratory routes) of spring migrations of Ospreys; (2) determine if differences in spring migration patterns existed between sexes and among three breeding populations (east coast, midwestern, and western); and (3) compare consecutive fall and spring migrations of individual Ospreys. The median dates for departure from the wintering grounds and arrival on the breeding grounds did not differ significantly between adult male and female Ospreys. Compared to their fall migrations, all male and all east coast Ospreys spent fewer days on migration, fewer days in stopover periods along the migration route, traveled shorter distances overall, and traveled farther (on average) each day during spring. In contrast, fall and spring migration characteristics of all female and western Ospreys were similar. Our findings suggest that, although sex and breeding location might influence the spring migration strategy used by individual Ospreys, both males and females minimize the time spent on migration to ensure a timely arrival on the breeding grounds to establish or defend a nesting territory. Migración Primaveral de Individuos Adultos de Pandion haliaetus La mayoría de los individuos de Pandion haliaetus son migratorios, reproduciéndose en latitudes hacia el norte y migrando largas distancias hacia y desde los sitios de invernada en los trópicos. Aunque los patrones de migración otoñal de P. haliaetus han sido descriptos y estudiados, se ha publicado muy poco sobre la migración primaveral de esta especie. Utilizamos telemetría satelital para: (1) determinar las características (tiempos, duración, rutas migratorias) de la migración primaveral de P. haliaetus; (2) determinar si las diferencias en los patrones de migración primaveral existieron entre sexos y entre tres poblaciones reproductivas (costa este, medio oeste y oeste); y (3) comparar migraciones consecutivas de otoño y primavera de individuos de P. haliaetus. Las fechas medianas de partida desde los sitios de invernada y de arribo a los sitios de reproducción no difirió significativamente entre individuos macho y hembra de P. haliaetus. En comparación con las migraciones otoñales, todos los individuos de P. haliaetus macho y todos los individuos de la costa este emplearon menos días migrando, menos días en periodos de descanso a lo largo de la ruta de migración, viajaron distancias más cortas en general y viajaron más lejos (en promedio) cada día durante la primavera. En contraste, las características migratorias de otoño y primavera de todos los individuos hembra y macho de P. haliaetus fueron similares. Estos hallazgos sugieren que aunque el sexo y la ubicación del sitio de reproducción pueden influir en la estrategia de migración primaveral utilizada por los individuos de P. haliaetus, tanto hembras como machos minimizan el tiempo empleado en la migración para asegurarse un arribo a tiempo a los sitios de reproducción para establecer o defender un territorio de nidada.

Temporal Variation in Terrestrial Invertebrate Consumption by Laughing Gulls in New York

Abstract Laughing gulls (Larus atricilla) are commonly found in many areas of North America and little is known about their diet, particularly in coastal-urban interfaces where gull-aircraft collisions can be a serious concern. The objective of this study was to describe and quantify the consumption of terrestrial invertebrates by laughing gulls at a coastal-urban interface in the northeastern United States. We examined the stomach contents of laughing gulls (n  =  1053) collected during wildlife damage management operations at John F. Kennedy International Airport during the summers of 2003 and 2004. Terrestrial invertebrates consumed by laughing gulls represented 2 taxonomic phyla, 4 classes, 15 orders and 40 families. Beetles (Coleoptera) and ants (Hymenoptera) were the most common terrestrial invertebrates consumed by laughing gulls. We found evidence of temporal (i.e., monthly) variation in the frequency of occurrence of terrestrial insects in laughing gull diets. Laughing gull gender and age did not influence the frequency of occurrence of terrestrial insects in gull diets. Terrestrial environments (e.g., areas of turfgrass) appear to provide important foraging locations and food resources for laughing gulls in coastal-urban areas. This information is important for developing effective management approaches to reduce human-gull conflicts, such as gull-aircraft collisions at coastal airports.