M. Clay Green

Land cover and bobwhite abundance on Oklahoma farms and ranches

To test prevailing paradigrns of habitat management for northern bobwhites (Colinus virginianus), we analyzed relations between the abundance of these birds, land-cover classes, and landscape metrics on Oklahoma farms and ranches (200-ha areas; n = 78) during 1998-1999. Based on replicated call-count indices, bobwhites declined (-0.03 to -0.07 males/ha; 95% confidence level here and below) with the quantity of an area in mature woodland, and increased (0.02 to 0.05 males/ha) with the quantity of brushy prairie or early successional woodland. We observed highest populations in the absence of cropland agriculture. Bobwhites declined as Shannon diversity of cover types (-6.0 to -0.01 males/Shannon unit), patch richness (-0.08 to -0.02 males/patch), and the density of woody edge (-0.027 to -0.003 males/m/ha) increased. Bobwhites responded more strongly to the composition of land-cover classes on areas than to the configuration of these classes in areas. Our results did not support the patchwork agriculture model of bobwhite abundance or the principle of edge. Results were consistent with a hypothesis that predicts bobwhite abundance is a nondecreasing function of usable space in time.

Comparison and Assessment of Aerial and Ground Estimates of Waterbird Colonies

Abstract Aerial surveys are often used to quantify sizes of waterbird colonies; however, these surveys would benefit from a better understanding of associated biases. We compared estimates of breeding pairs of waterbirds, in colonies across southern Louisiana, USA, made from the ground, fixed-wing aircraft, and a helicopter. We used a marked-subsample method for ground-counting colonies to obtain estimates of error and visibility bias. We made comparisons over 2 sampling periods: 1) surveys conducted on the same colonies using all 3 methods during 3–11 May 2005 and 2) an expanded fixed-wing and ground-survey comparison conducted over 4 periods (May and Jun, 2004–2005). Estimates from fixed-wing aircraft were approximately 65% higher than those from ground counts for overall estimated number of breeding pairs and for both dark and white-plumaged species. The coefficient of determination between estimates based on ground and fixed-wing aircraft was ≤0.40 for most species, and based on the assumption that estimates from the ground were closer to the true count, fixed-wing aerial surveys appeared to overestimate numbers of nesting birds of some species; this bias often increased with the size of the colony. Unlike estimates from fixed-wing aircraft, numbers of nesting pairs made from ground and helicopter surveys were very similar for all species we observed. Ground counts by one observer resulted in underestimated number of breeding pairs by 20% on average. The marked-subsample method provided an estimate of the number of missed nests as well as an estimate of precision. These estimates represent a major advantage of marked-subsample ground counts over aerial methods; however, ground counts are difficult in large or remote colonies. Helicopter surveys and ground counts provide less biased, more precise estimates of breeding pairs than do surveys made from fixed-wing aircraft. We recommend managers employ ground counts using double observers for surveying waterbird colonies when feasible. Fixed-wing aerial surveys may be suitable to determine colony activity and composition of common waterbird species. The most appropriate combination of survey approaches will be based on the need for precise and unbiased estimates, balanced with financial and logistical constraints.

Modeling artificial light viewed by fledgling seabirds

Artificial light is increasing in coverage across the surface of our planet, impacting the behavioral ecology of many organisms. Attraction to sources of artificial light is a significant threat to certain fledgling shearwaters, petrels (Procellariidae), and storm-petrels (Hydrobatidae) on their first nocturnal flights to the sea. Disorientation by light can cause these birds to crash into vegetation or manmade structures, potentially resulting in death from physical injury, starvation, dehydration, predation by introduced predators, or collisions with vehicles. We developed a GIS-based method to model the intensity of artificial light that fledgling procellariids and hydrobatids could view en route to the ocean (to estimate the degree of threat that artificial light poses to these birds) and present two models for the island of Kauai as examples. These models are particularly relevant to the federally threatened Newells Shearwater, or `A`o (Puffinus newelli), of which >30,000 fledglings have been collected in response to disorientation by lights on Kauai during the past 30 years. Our models suggest that there are few to no portions of Kauai from which young birds could fledge and not view light on their post-natal nocturnal flights, which is concerning given evidence of a Newells Shearwater population decline. In future work using this technique, night light intensity layers could be altered to model the effects of modified coastal light conditions on known and potential procellariid and hydrobatid breeding locations. Furthermore, certain methods presented herein may be applicable to other seabirds and additional taxa in which attraction to anthropogenic light poses a serious threat, including migratory passerines and hatchling marine turtles. Components of this modeling approach could potentially be used to spatially estimate effects of other point-source threats to ecological systems, including sound and air pollution.

Plumage Dimorphism in the Reddish Egret: Does Plumage Coloration Influence Foraging Habitat Use and Tactics?

Abstract One possible explanation for the evolution of white plumage in herons is an adaptive advantage for foraging. Under this hypothesis, white plumage is cryptic to aquatic prey; thus white-plumaged birds may be more prone to forage in deep water habitats, where they would be cryptic, using passive foraging tactics. Dark-plumaged birds foraging in shallow water habitats, where they are presumably more visible, use active tactics. These hypotheses were tested by investigating choice of water depth and choice of foraging tactics by conducting paired foraging observations between color morphs within the plumage dimorphic Reddish Egret (Egretta rufescens). Water was divided into four depths classes: deep (>15 cm), intermediate (5-15 cm), shallow (1-5 cm), and mudflat (<1 cm). There was no difference in time spent in different water depth classes between the two color morphs of the Reddish Egret. However, there was a significant interaction between color morph and depth of water for time spent actively foraging. The white morph of the Reddish Egret was more active in intermediate depths of water than the dark morph while the dark morph was more active in shallow depths of water. These results support the hypothesis that Reddish Egrets may alter foraging tactics based on their degree of crypsis to prey.

Influence of plumage colour on prey response: does habitat alter heron crypsis to prey?

The foraging strategies of wading birds may be influenced by their degree of crypsis to aquatic prey. White plumage has been hypothesized to be adaptive for herons hunting in open water habitats. We tested this hypothesis with laboratory and field experiments with multiple prey species. We investigated the response of crayfish, Procambarus spp., and mosquitofish, Gambusia affinis, to white- and dark-plumaged birds in an experimental chamber. We compared the time spent by a prey in front of a snowy egret, Egretta thula, mount, little blue heron, E. caerulea, mount, and a control (dowel) with and without backdrop vegetation. Mosquitofish tended to spend less time under the little blue heron mount with no backdrop present but made no observable response to either plumage colour against a vegetative backdrop. We assessed prey response in the field using three drop traps. Each trap had either a little blue heron mount, a snowy egret mount or a control (dowel) mounted underneath a trap. We compared the amount of biomass captured between treatments. More prey biomass (mosquitofish, crayfish and anurans) was captured under the control and snowy egret treatments than under the little blue heron treatment. Our results suggest that dark plumage may be a disadvantage to herons foraging in open water. In vegetation, structural complexity of the habitat appears to nullify differences in plumage colour between white and dark foraging herons.

Status of Breeding Reddish Egrets on Great Inagua, Bahamas with Comments on Breeding Territoriality and the Effects of Hurricanes

Abstract. The Commonwealth of the Bahamas is an important region to Reddish Egrets (Egretta rufescens); however, current status of this species in the Bahamas is lacking. From 2008–2010, a breeding survey of Reddish Egrets was conducted in Great Inagua to 1) document breeding status, 2) document breeding phenology, and 3) estimate the number of breeding pairs. A total of 87 Reddish Egret nests on Great Inagua over two breeding seasons were recorded; the proportion of white, dark and mixed-morph nesting pairs varied but averaged (±S.D.) 68.4 ± 7.5, 18.2 ± 2.4, and 13.4 ± 5.1%, respectively. Based on these surveys, the breeding season range extends from December to May, varying annually due to changes in precipitation. Territorial aggression of solitary nesting pairs in Reddish Egrets was observed, previously unreported for the Caribbean. Damage to mangrove islands from Hurricane Ike in September 2008 appeared to increase nesting concentrations on Lake Rosa; solitary nesting decreased from 36% before, to 10% after the hurricane. Because the surveys before and after the hurricane did not encompass the entire breeding seasons, increased concentration of nesting may have been influenced by other factors besides Hurricane Ike. Even with incomplete breeding season surveys, these estimates of nesting pairs indicate a >50% decrease in number of breeding pairs of Reddish Egret on Great Inagua since the 1980s; this is a conservation concern as the population is distinct.

Microsatellite Variation of Double-Crested Cormorant Populations in Eastern North America

Double-crested cormorants (Phalacrocorax auritus) exhibit highly adaptive and opportunistic foraging behavior. This flexibility in foraging and increases in population size have led to conflicts with aquaculture and recreational and commercial fishing (Duffy 1995). Although double-crested cormorants roosting in the lower Mississippi Valley appear to have minimal negative impact on sport fisheries, they may have a significant impact on commercial aquaculture production in this region (Glahn and Brugger 1995, Glahn et al. 1998). In 2003, the U.S. Fish and Wildlife Service released the Final Environmental Impact Statement on doublecrested cormorant management allowing more flexibility in control of these birds in areas where they are negatively impacting aquaculture, habitat for nesting colonial waterbirds, and other public resources (U.S. Fish and Wildlife Service 2003). The U.S. Fish and Wildlife Service’s Final Rule expands the 1998 Public Resource Depredation Order (50 CFR 21.47) to permit control of double-crested cormorants at winter roost sites in the vicinity of aquaculture facilities. Populations of double-crested cormorants declined sharply in the 19th and early 20th centuries followed by several periods of population growth in the middle and later decades of the 20th century (Hatch 1995). Atlantic and Interior/Great Lakes migratory populations have seen the greatest increase in breeding pairs. Between the 1970s and 1990s, double-crested cormorant populations in the Atlantic increased 4-fold to more than 96,000 pairs (Hatch 1995). Although double-crested cormorants experienced a marked increase in population size from the 1970s to the 1990s, recent estimates suggest a reduction in the overall rate of growth (Tyson et al. 1999). Although most populations of double-crested cormorants are migratory, a resident population (P. auritus subsp. floridanus) estimated at 10,000–30,000 individuals occurs in Florida (Brugger 1995, Hatch 1995). Population estimates for Florida suggest stable resident populations of P. auritus subsp. floridanus with increasing numbers of wintering birds from migratory subpopulations (Brugger 1995). It is unclear whether or not the resident subspecies in Florida is a genetically distinct lineage, separate from migratory populations. If genetic differentiation is sufficient, it is possible that this resident population may warrant special consideration in management and any control efforts. In addition to the population in Florida, smaller colonies of nonmigratory birds have become established in other areas of the southeastern United States (e.g., Mississippi Delta, Reinhold et al. 1998; Louisiana, Hatch and Weseloh 1999). Determining genetic distinctiveness of diverse populations of double-crested cormorants and the extent of gene flow are important for regional management decisions (Hatch and Weseloh 1999). It is thought that individuals exhibit high fidelity to a colony site; although, no data exist to support this claim (Hatch and Weseloh 1999). Reduction of populations on breeding grounds might prove more feasible than reduction of wintering birds because double-crested cormorants nest in distinct colonies that can be readily accessed. Control efforts on breeding grounds would be most effective at reducing depredation if the natal areas of wintering birds can be identified. The number of band returns is insufficient to establish a relationship between double-crested cormorant nesting colonies in the northern United States and Canada and the wintering, depredating populations in the southeastern United States. Genetic markers have been used to associate wintering dunlin (Calidris alpina) and Canada geese (Branta canadensis) with breeding populations (Pierson et al. 2000, Wennerberg 2001). Sufficient genetic differentiation among breeding populations is necessary to correctly assign samples of wintering birds to their natal areas. An analysis of variation in mitochondrial DNA (mtDNA) found no evidence of genetic differences among migratory and nonmigratory populations (Waits et al. 2003). However, microsatellite loci are known to evolve rapidly and, thus, may reveal population structure even in the absence of mtDNA structure. For example, Goostrey et al. (1998) used highly polymorphic microsatellite markers to assess population structure and differentiation in European populations of great cormorants (P. carbo subsp. sinensis and P. carbo subsp. carbo). They detected high levels of variation both within and among populations suggesting the potential for detecting differences among populations of double-crested cormorants. Our primary objectives are to 1) characterize the genetic 1 E-mail: claygreen@txstate.edu 2 Present address: Department of Biology, Texas State University, San Marcos, TX 78666, USA 3 Present address: Department of Biology, University of Memphis, Memphis, TN 38152, USA

Habitat Selection by Collared Peccaries in Trans-pecos Texas

ry and home range are compatible and used interchangeably in most literature on collared peccaries (Sowls, 1997). Although collared peccaries are relatively abundant in the TransPecos region, only 2 published studies on population ecology have been conducted. Bissonette (1978) investigated influence of temperature extremes on collared peccary behavior in Big Bend National Park, Texas. In all seasons, collared peccary herds bedded during temperature extremes, whether day or night, and were most active at intermediate temperatures. Research using radio telemetry has been conducted to determine home ranges of collared peccaries in Arizona and south Texas, but not in Trans-Pecos Texas. Bissonette (1982) also observed collared peccary herds at Big Bend National Park investigating herd size, home range, behavior, and group dynamics utilizing visual observation in lieu of radio tracking. These observations were limited to 2 lower el-

Habitat Suitability Modeling for the Newell's Shearwater on Kauai

Abstract The Newells shearwater, or ‘A’o Puffinus newelli, is endemic to the main islands of the Hawaiian Archipelago and is listed as endangered on the International Union for Conservation of Nature Red List and as threatened under the U.S. Endangered Species Act. Using abiotic and biotic environmental variables, we developed a terrestrial habitat suitability model for this species on Kauai to predict habitat that could be suitable in the absence of anthropogenic threats. In addition, we developed a habitat/threat-isolation index incorporating information from our suitability model to identify regions of structurally suitable habitat with less exposure to certain anthropogenic threats (relative to other portions of the island). The habitat suitability model suggests that slope, density of rock fragments within the soil, and native vegetation cover are important factors associated with the current known distribution of the Newells shearwater on Kauai, and that a moderate portion of the sloped interior t...

Potential Factors Affecting Nest Initiation Date, Clutch Size and Nest Success in the Plumage Dimorphic Reddish Egret

Abstract. Plumage dimorphism is common in the family Ardeidae with one morph possessing all-white plumage and the alternate morph being darkly colored. The effects of plumage morph and colony site on nest initiation date, clutch size and total nest success of the plumage dimorphic Reddish Egret in the Laguna Madre region of Texas were examined. Color morph did not significantly affect nest initiation date (Julian date - Dark morph: 109.88 (S.D. 26.56), White morph: 100.82 (25.85), Mixed-morph: 113.29 (27.55); ANOVA: F(2,158)= 0.199, P = 0.820) although nest initiation date was different between nesting colonies (Julian date - Rabbit Island: 125.14 (S.D. 18.05); Zigzag Island: 87.15 (19.07); ANOVA: F(1,158) = 5.732, P = 0.018). Overall mean (±S.E.) clutch size was 3.29 ± 0.05 and differed between colony sites but not between color morphs. Model selection analysis using logistic exposure revealed that neither plumage morph nor colony site had a significant effect on nest success. Mayfield total nest success was estimated at 85.10% ± 5.4% (n = 171), results which are similar to nesting success estimates in other heron species. The lack of effect of color morph on timing of nest initiation, clutch size and nest success suggests other factors may influence the maintenance of color dimorphism in Reddish Egrets.