David J. Delehanty

Stress and translocation: alterations in the stress physiology of translocated birds

Translocation and reintroduction have become major conservation actions in attempts to create self-sustaining wild populations of threatened species. However, avian translocations have a high failure rate and causes for failure are poorly understood. While ‘stress’ is often cited as an important factor in translocation failure, empirical evidence of physiological stress is lacking. Here we show that experimental translocation leads to changes in the physiological stress response in chukar partridge, Alectoris chukar. We found that capture alone significantly decreased the acute glucocorticoid (corticosterone, CORT) response, but adding exposure to captivity and transport further altered the stress response axis (the hypothalamic–pituitary–adrenal axis) as evident from a decreased sensitivity of the negative feedback system. Animals that were exposed to the entire translocation procedure, in addition to the reduced acute stress response and disrupted negative feedback, had significantly lower baseline CORT concentrations and significantly reduced body weight. These data indicate that translocation alters stress physiology and that chronic stress is potentially a major factor in translocation failure. Under current practices, the restoration of threatened species through translocation may unwittingly depend on the success of chronically stressed individuals. This conclusion emphasizes the need for understanding and alleviating translocation-induced chronic stress in order to use most effectively this important conservation tool.

Nest Predation of Greater Sage-Grouse in Relation to Microhabitat Factors and Predators

Abstract Nest predation is a natural component of greater sage-grouse (Centrocercus urophasianus) reproduction, but changes in nesting habitat and predator communities may adversely affect grouse populations. We used a 2-part approach to investigate sage-grouse nest predation. First, we used information criteria to compare nest survival models that included indices of common raven (Corvus corax) abundance with other survival models that consisted of day of incubation, grouse age, and nest microhabitat covariates using measurements from 77 of 87 sage-grouse nests. Second, we used video monitoring at a subsample of 55 of 87 nests to identify predators of depredated nests (n  =  16) and evaluated the influence of microhabitat factors on the probability of predation by each predator species. The most parsimonious model for nest survival consisted of an interaction between day of incubation and abundance of common ravens (wraven×incubation day  =  0.67). An estimated increase in one raven per 10-km transect survey was associated with a 7.4% increase in the odds of nest failure. Nest survival was relatively lower in early stages of incubation, and this effect was strengthened with increased raven numbers. Using video monitoring, we found the probability of raven predation increased with reduced shrub canopy cover. Also, we found differences in shrub canopy cover and understory visual obstruction between nests depredated by ravens and nests depredated by American badgers (Taxidea taxus). Increased raven numbers have negative effects on sage-grouse nest survival, especially in areas with relatively low shrub canopy cover. We encourage wildlife managers to reduce interactions between ravens and nesting sage-grouse by managing raven populations and restoring and maintaining shrub canopy cover in sage-grouse nesting areas.

Effects of Environmental Factors on Incubation Patterns of Greater Sage-Grouse

Abstract Birds in which only one sex incubates the eggs are often faced with a direct conflict between foraging to meet metabolic needs and incubation. Knowledge of environmental and ecological factors that shape life-history strategies of incubation is limited. We used continuous videography to make precise measurements of female Greater Sage-Grouse (Centrocercus urophasianus) incubation constancy (percentage of time spent at the nest in a 24-hour period) and recess duration. We used an information-theoretic approach to evaluate incubation patterns in relation to grouse age, timing of incubation, raven abundance, microhabitat, weather, and food availability. Overall, sage-grouse females showed an incubation constancy of 96% and a distinctive bimodal distribution of brief incubation recesses that peaked at sunset and 30 min prior to sunrise. Grouse typically returned to their nests during low light conditions. Incubation constancy of yearlings was lower than that of adults, particularly in the later stages of incubation. Yearlings spent more time away from nests later in the morning and earlier in the evening compared to adults. Video images revealed that nearly all predation events by Common Ravens (Corvus corax), the most frequently recorded predator at sage-grouse nests, took place during mornings and evenings after sunrise and before sunset, respectively. These were the times of the day when sage-grouse typically returned from incubation recesses. Recess duration was negatively related to raven abundance. We found evidence that incubation constancy increased with greater visual obstruction, usually from vegetation, of nests. An understanding of how incubation patterns relate to environmental factors will help managers make decisions aimed at increasing productivity through successful incubation.

Selection of anthropogenic features and vegetation characteristics by nesting Common Ravens in the sagebrush ecosystem

ABSTRACT Common Raven (Corvus corax) numbers and distribution are increasing throughout the sagebrush steppe, influencing avian communities in complex ways. Anthropogenic structures are thought to increase raven populations by providing food and nesting subsidies, which is cause for concern because ravens are important nest predators of sensitive species, including Greater Sage-Grouse (Centrocercus urophasianus). During 2007–2009, we located raven nests in southeastern Idaho and conducted a resource selection analysis. We measured variables at multiple spatial scales for 72 unique nest locations, including landscape-level vegetation characteristics and anthropogenic structures. Using generalized linear mixed models and an information-theoretic approach, we found a 31% decrease in the odds of nesting by ravens for every 1 km increase in distance away from a transmission line. Furthermore, a 100-m increase in distance away from the edge of two different land cover types decreased the odds of nesting by 20%, and an increase in the amount of edge by 1 km within an area of 102.1 ha centered on the nest increased the odds of nesting by 49%. A post hoc analysis revealed that ravens were most likely to nest near edges of adjoining big sagebrush (Artemisia tridentata) and land cover types that were associated with direct human disturbance or fire. These findings contribute to our understanding of raven expansion into rural environments and could be used to make better-informed conservation decisions, especially in the face of increasing renewable energy development.

Landscape alterations influence differential habitat use of nesting buteos and ravens within sagebrush ecosystem: Implications for transmission line development

ABSTRACT A goal in avian ecology is to understand factors that influence differences in nesting habitat and distribution among species, especially within changing landscapes. Over the past 2 decades, humans have altered sagebrush ecosystems as a result of expansion in energy production and transmission. Our primary study objective was to identify differences in the use of landscape characteristics and natural and anthropogenic features by nesting Common Ravens (Corvus corax) and 3 species of buteo (Swainsons Hawk [Buteo swainsoni], Red-tailed Hawk [B. jamaicensis], and Ferruginous Hawk [B. regalis]) within a sagebrush ecosystem in southeastern Idaho. During 2007–2009, we measured multiple environmental factors associated with 212 nest sites using data collected remotely and in the field. We then developed multinomial models to predict nesting probabilities by each species and predictive response curves based on model-averaged estimates. We found differences among species related to nesting substrate (natural vs. anthropogenic), agriculture, native grassland, and edge (interface of 2 cover types). Most important, ravens had a higher probability of nesting on anthropogenic features (0.80) than the other 3 species (<0.10), and the probability of nesting near agriculture was greatest for ravens (0.55) followed by Swainsons Hawk (0.28). We also describe changes in nesting densities over 4 decades at this site as related to natural and anthropogenic disturbances. Since the 1970s, the composition of the raptor and raven nesting community has drastically changed with anthropogenic alterations and loss of continuous stands of sagebrush (Artemisia spp.), favoring increased numbers of nesting ravens and fewer nesting Ferruginous Hawks. Our results indicate that habitat alterations, fragmentation, and forthcoming disturbances anticipated with continued energy development in sagebrush steppe ecosystems can lead to predictable changes in raptor and raven communities.

Greater sage-grouse nest predators in the Virginia Mountains of northwestern Nevada

Abstract Greater sage-grouse Centrocercus urophasianus, hereafter sage-grouse, populations have declined across their range due to the loss, degradation, and fragmentation of habitat. Habitat alterations can lead not only to vegetative changes but also to shifts in animal behavior and predator composition that may influence population vital rates, such as nest success. For example, common ravens Corvus corax are sage-grouse nest predators, and common raven abundance is positively associated with human-caused habitat alterations. Because nest success is a central component to sage-grouse population persistence, research that identifies factors influencing nest success will better inform conservation efforts. We used videography to unequivocally identify sage-grouse nest predators within the Virginia Mountains of northwestern Nevada, USA, from 2009 to 2011 and used maximum likelihood to calculate daily probability of nest survival. In the Virginia Mountains, fires, energy exploration, and other anthropogeni...

Mountain quail fidelity to guzzlers in the Mojave Desert

Wildlife Society Bulletin 2004, 32(2):588–593 Peer edited Self-filling wildlife watering devices, originally named “gallinaceous guzzlers,” were developed in California during the early 1940s to promote desert populations of quail (Glading 1943). A guzzler functions by collecting seasonal precipitation into a water storage tank equipped with an access point that allows wildlife to drink stored water during dry periods. Many types of guzzlers now exist, and guzzler installation to provide water for birds and mammals has become a prominent wildlife management action throughout the arid American West (Rosenstock et al. 1999). Given the substantial human and material investment in guzzler installation, it is important to ask, how do target species use guzzlers? Little published research has addressed use of guzzlers by New World quail (Odontophoridae) or other wildlife,and we have a poor understanding of how guzzlers influence wildlife populations (Campbell 1960, Broyles 1995, Rosenstock et al. 1999, Broyles and Cutler 2001a). Data addressing how wildlife use guzzlers would be helpful at several levels. It is desirable to know the results of the substantial investment in guzzlers to judge whether continued investment is merited (Campbell 1960, Rosenstock et al. 1999, Broyles and Cutler 2001b). Also, some have questioned the benefit of guzzlers to the species they are intended to aid (Campbell 1960, Connelly and Doughty 1988, Burkett and Thompson 1994, Broyles 1995) or conjectured that guzzler installation may be detrimental by aiding expansion of undesired species such as competitors or predators of the species intended to be helped (Broyles 1995). These are important management issues. Measuring how target species use guzzlers is a valuable first step in addressing these issues objectively. Additionally, by measuring how individual animals use guzzlers, we can begin to understand behavioral mechanisms underlying population responses to the presence of guzzlers. We measured guzzler use by mountain quail (Oreortyx pictus) in the Mojave Desert. Our objective was to assess how individual mountain quail use individual guzzlers over time rather than simply to survey presence or absence of mountain quail at guzzlers. Specifically, we tested whether individual mountain quail persistently used a single guzzler within an array of guzzlers or individuals moved among multiple guzzlers. Serial use of multiple guzzlers would indicate that individual quail have knowledge of >1 water source and that a single guzzler likely is not an essential source of water. Persistent use of a single guzzler,on the other hand, would suggest the potential for dependence on that water source and magnify the importance of a single guzzler to the local population, particularly if individuals restrict their movements to remain close to the water source.

Integrating spatially explicit indices of abundance and habitat quality: an applied example for greater sage-grouse management.

Summary Predictive species distributional models are a cornerstone of wildlife conservation planning. Constructing such models requires robust underpinning science that integrates formerly disparate data types to achieve effective species management. Greater sage‐grouse Centrocercus urophasianus, hereafter ‘sage‐grouse’ populations are declining throughout sagebrush‐steppe ecosystems in North America, particularly within the Great Basin, which heightens the need for novel management tools that maximize the use of available information. Herein, we improve upon existing species distribution models by combining information about sage‐grouse habitat quality, distribution and abundance from multiple data sources. To measure habitat, we created spatially explicit maps depicting habitat selection indices (HSI) informed by >35 500 independent telemetry locations from >1600 sage‐grouse collected over 15 years across much of the Great Basin. These indices were derived from models that accounted for selection at different spatial scales and seasons. A region‐wide HSI was calculated using the HSI surfaces modelled for 12 independent subregions and then demarcated into distinct habitat quality classes. We also employed a novel index to describe landscape patterns of sage‐grouse abundance and space use (AUI). The AUI is a probabilistic composite of the following: (i) breeding density patterns based on the spatial configuration of breeding leks and associated trends in male attendance; and (ii) year‐round patterns of space use indexed by the decreasing probability of use with increasing distance to leks. The continuous AUI surface was then reclassified into two classes representing high and low/no use and abundance. Synthesis and applications. Using the example of sage‐grouse, we demonstrate how the joint application of indices of habitat selection, abundance and space use derived from multiple data sources yields a composite map that can guide effective allocation of management intensity across multiple spatial scales. As applied to sage‐grouse, the composite map identifies spatially explicit management categories within sagebrush steppe that are most critical to sustaining sage‐grouse populations as well as those areas where changes in land use would likely have minimal impact. Importantly, collaborative efforts among stakeholders guide which intersections of habitat selection indices and abundance and space use classes are used to define management categories. Because sage‐grouse are an umbrella species, our joint‐index modelling approach can help target effective conservation for other sagebrush obligate species and can be readily applied to species in other ecosystems with similar life histories, such as central‐placed breeding.

Using Sharp-Tailed Grouse Movement Patterns to Guide Release-Site Selection

Abstract Prairie grouse populations are difficult to reestablish after extirpation. Following translocation, distances individuals move from the release site appear to affect restoration success. Previous authors have suggested assessing lek, nest–brood, and winter habitat when selecting release sites. We examined movement of 131 (66 M and 65 F) radiomarked Columbian sharp-tailed grouse (Tympanuchus phasianellus columbianus) translocated during 1999–2002 as part of management effort to restore populations to historical ranges in northeastern Nevada, USA, an area where sharp-tailed grouse have not been observed in the wild since the 1950s. We released grouse at 2 sites. We chose the initial site based on its physiographic and vegetation similarities to capture sites in Idaho, USA, particularly shrub–steppe at lower elevations and mountain shrub at higher elevations, and used it during 1999 and 2000 (34 M, 18 F in 1999; 42 M, 26 F in 2000). Females released at this site moved greater distances than males through time, with no differences between years. We changed the release site based on nest locations of previously translocated females. The second site was 10 km south of site 1 and we used it in 2001 and 2002 (36 M, 22 F in 2001; 14 M, 5 F in 2002). Grouse released at this site moved substantially shorter distances than did the grouse initially released, and movement distances did not differ by gender or year. During 2004 we observed 23 grouse displaying on a lek near site 2 and observed no grouse near site 1. Our results support the hypothesis that nest-site availability is an important component to release-site selection insofar as sharp-tailed grouse in our study moved less when released into habitat that had been selected for nesting by previously released grouse.

Effect of capture date on nest-attempt rate of translocated sharp-tailed grouse Tympanuchus phasianellus

Abstract Attempts to establish functioning populations of prairie grouse by translocation often are unsuccessful due to low reproduction following release. We examined the relationship between capture date and nest attempts of Columbian sharp-tailed grouse Tympanuchus phasianellus columbianus during an effort to restore them by translocation to their historic range in northeastern Nevada, USA, during 1999–2000. After observing that females captured relatively early in the trapping period did not attempt to nest, we hypothesized that the likelihood of female insemination is positively correlated to capture date. If females captured at source leks later in the breeding season are more likely to be inseminated, then they may be more likely to nest following release than females that are not inseminated prior to capture. We found that female grouse that were captured from source leks at later dates during the lek-visitation period were more likely to nest following translocation than were females captured during the initial days of female visitation to leks (LogXact Test: P = 0.001). Of 40 radio-marked female grouse, 19 (48%) were observed nesting and nest success was 44%. During 2001, we tested the effect of capture date on the presence of spermatozoa in live female grouse captured from leks. Females trapped later in the lek-visitation period were more likely inseminated than females captured early in the lek-visitation period (LogXact Test: P = 0.036). We recommend that wildlife managers consider capturing females from source leks several days following the onset of the lek-visitation period to increase the frequency of female nest attempts and increase the probability of establishing a new population during reintroductions.