International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / GPS signal fixed dwell and variable dwell time sequential search algorithms are compared with probability of false alarm and detection and searching rate. An adaptive search algorithm is proposed according to different work modes and interference or jam circumstance, which has effectively improved signal acquiring speed and reliability. Mathematical simulation shows its correction and feasible.

Several species of small, cavity-nesting owls occur in the Sierra Nevada, including in areas impacted by human activities. The owls typically use standing dead trees (snags) for nest sites. Although descriptive studies exist regarding habitats associations around nest and roost sites, few studies have examined habitat associations at larger spatial scales or relative to certain snag characteristics (e.g., density, decay class). To improve our understanding of the habitat associations of these owls, I compared habitat characteristics at 2 spatial scales around areas of owl detection and non-detection. I also examined distances between conspecifics and heterospecifics to determine if clustering of conspecifics or avoidance of predators occurred. I conducted owl broadcast surveys and snag sampling during the spring and summer of 2006 and 2007 in the Lake Tahoe Basin of central Sierra Nevada. I measured additional habitat variables (e.g., vegetation cover, distance to roadways) from pre-existing geographical information system layers. I used stepwise logistic regression to ascertain which variables were influential in predicting owl occurrence. The northern saw-whet owl (Aegolius acadicus) was the only species detected in sufficient numbers for statistical analysis, with a detection probability of 0.25. I detected saw-whets in a wide range of conditions and it appeared that few factors influenced their distribution in the basin. Areas dominated by white fir, however, were correlated with the absence of saw-whets at both the macrohabitat and microhabitat scales. White fir-dominated areas tend to occur on the west side of the basin and it is possible white fir was acting as a proxy for other factors not measured in this study, such as microclimate conditions or prey availability. I was also more likely to find a saw-whet within 1000 m of another saw-whet than within 1000 m of a non-use point, indicating clustering of conspecifics in the basin. While it appears saw-whet needs are being met in the basin, restoration projects are ongoing to decrease both the number of snags and relative abundance of white fir. Continued monitoring of the species is essential to understand potential effects of restoration activities. Suggestions are provided for appropriate timing and effort of future surveys.

Several species of small, cavity-nesting owls occur in the Sierra Nevada, including in areas impacted by human activities. The owls typically use standing dead trees (snags) for nest sites. Although descriptive studies exist regarding habitats associations around nest and roost sites, few studies have examined habitat associations at larger spatial scales or relative to certain snag characteristics (e.g., density, decay class). To improve our understanding of the habitat associations of these owls, I compared habitat characteristics at 2 spatial scales around areas of owl detection and non-detection. I also examined distances between conspecifics and heterospecifics to determine if clustering of conspecifics or avoidance of predators occurred. I conducted owl broadcast surveys and snag sampling during the spring and summer of 2006 and 2007 in the Lake Tahoe Basin of central Sierra Nevada. I measured additional habitat variables (e.g., vegetation cover, distance to roadways) from pre-existing geographical information system layers. I used stepwise logistic regression to ascertain which variables were influential in predicting owl occurrence. The northern saw-whet owl (Aegolius acadicus) was the only species detected in sufficient numbers for statistical analysis, with a detection probability of 0.25. I detected saw-whets in a wide range of conditions and it appeared that few factors influenced their distribution in the basin. Areas dominated by white fir, however, were correlated with the absence of saw-whets at both the macrohabitat and microhabitat scales. White fir-dominated areas tend to occur on the west side of the basin and it is possible white fir was acting as a proxy for other factors not measured in this study, such as microclimate conditions or prey availability. I was also more likely to find a saw-whet within 1000 m of another saw-whet than within 1000 m of a non-use point, indicating clustering of conspecifics in the basin. While it appears saw-whet needs are being met in the basin, restoration projects are ongoing to decrease both the number of snags and relative abundance of white fir. Continued monitoring of the species is essential to understand potential effects of restoration activities. Suggestions are provided for appropriate timing and effort of future surveys.

Effective conservation requires efficient population monitoring, which can be challenging for rare species like the desert tortoise (Gopherus agassizii). We compared two alternative survey methods that can be used to monitor tortoise populations: distance sampling and site occupancy estimation. In 2005 and 2006 combined, we surveyed 120 1-km transects to estimate density and 40 3-ha plots with five presence-“absence” surveys to estimate occupancy of Sonoran desert tortoises in two mountain ranges in southern Arizona. We found that monitoring programs based on an occupancy framework were more efficient and had greater power to detect linear trends. We also found that habitat use by Sonoran desert tortoises was influenced most by slope and aspect, contrasting with patterns observed in the Mojave Desert. Given its efficiency, power, and ability to gauge changes in distribution while accounting for variation in detectability, occupancy offers a promising alternative for long-term monitoring of Sonoran desert tortoise populations.

Aquatic biodiversity continues to decline as humans modify the landscape. A population-level approach is necessary to address the mechanisms of impairment in urban stream habitats. When estimating population-level parameters, incomplete detection of individuals must be accounted for to ensure unbiased estimates. In this thesis, I examined differences in the detection probabilities of stream fishes, and used estimates of size/age-specific detection probabilities to reduce bias in estimates of the reproductive success of various fish species in urban and forested stream habitats. In Chapter 1, I examined differences in detection probabilities of stream fishes among electrofishing passes and size/age groups in the middle New River basin, Virginia. I also examined differences in detection probabilities between two physiographic regions: the middle New River basin, and the upper Wabash River basin, Indiana; and evaluated differences between single- and multiple-season estimation methods. I found that for most species, detection probabilities do not differ among electrofishing passes, size/age classes, between the two regions, or between single- and multiple-season estimation methods. I used size/age-specific estimates of detection probabilities to remove bias from relative abundance estimates of steam fish populations in Chapter 2. In Chapter 2, I examined the reproductive success of six lithophilic and speleophilic fishes in urban and forested reaches of 2nd-4th Strahler-order streams in the middle New River basin. I found that binary classification is a poor method of quantifying reproductive success, that the age distributions of many lithophilic and speleophilic species are dominated by adult individuals in urban habitats, and that the population growth rates of speleophils is reduced in urban habitats. These results suggest that although detection probabilities may be equal among various sources of variation, managers should verify this assumption before assuming equal detectability. The results also suggest that reduced reproductive success of speleophilic and lithophilic species in urban stream habitats may be a mechanism of their impairment. / Master of Science

Wetlands of the Prairie Pothole Region (PPR) provide important breeding habitat for greater than 30 species of waterbirds. Approximately 70% of PPR wetlands have been lost since European settlement and remaining wetlands are subjected to frequent degradation, primarily due to agricultural activities. Horned grebes (Podiceps auritus) are experiencing long-term population declines and are listed as a species of Special Concern in Canada. Because there is virtually no information on the status and trends of pied-billed grebes (Podilymbus podicep) this species is also of considerable conservation concern. Grebes are recorded on the Waterfowl Breeding Population and Habitat Surveys (WBPHS) conducted annually in May by the Canadian Wildlife Service; however, how accurately these counts reflect actual abundance has been unknown. Using a repeated counts method in 2010 and 2011, estimates of detection probabilities averaged 0.48 and 0.18 for horned and pied-billed grebes, respectively. These results suggest that WBPHS ground surveys may be used as an efficient and effective management tool for monitoring horned grebe abundances. However, low detection rates for pied-billed grebes lend little support for including the species in future monitoring efforts using the WBPHS. I recommend that the Canadian Wildlife Service consider implementing standardized ground survey methods to facilitate annual monitoring of horned grebe abundances. Marshbird research has focused primarily on breeding habitat use or selection but has seldom examined how productivity is related to wetland characteristics. Understanding processes that affect distribution patterns and productivity of grebes could provide insights into actions needed to achieve conservation goals. Therefore, occupancy of wetlands by breeding and brood-rearing horned and pied-billed grebes was evaluated on 6-7 study sites (5.8-11.6 km2) in south-central Saskatchewan, 2010 and 2011, and related to wetland and upland habitat features. Wetland occupancy by grebes was influenced by interspecific competition as well as local and landscape-level wetland features. Horned and pied-billed grebes rarely co-occurred on smaller (≤4 ha) semi-permanent and permanent wetlands. At the wetland level, horned grebe occupancy and productivity were highly correlated with the amount of emergent vegetation, whereas wetland area alone was a better predictor of adult pied-billed grebe occupancy and productivity. At a landscape level, the number of semi-permanent, permanent, and artificial wetlands on each study site was an important predictor of breeding and brood-rearing wetland occupancy probability for horned grebes in 2010 and for pied-billed grebes in both years. However, breeding horned grebe occupancy probability and productivity were higher in low wetland density landscapes in 2011. Horned grebes may be opportunistic, exploiting more of the available wetland habitats in low wetland density landscapes during years of above-average water conditions. Conservation initiatives for grebes should consider the roles of wetland-specific and landscape-level features while protecting semi-permanent and permanent wetlands in landscapes characterized by both high and low wetland densities.

The black caiman (Melanosuchus niger) and the yacare caiman (Caiman yacare) have in the past been exposed to overexploitation due to the economic profit for their hides, and therefore suffered from great declines in population sizes, especially black caimans. Legal regulation efforts made it possible for these two species to recover and today they are widely distributed in South America. Evaluation of protection and management of populations of top predators like these caimans depend on the ability to detect the animals. The probability of detecting a crocodile, or any animal, is affected by several factors such as habitat complexity and behaviour why it is of importance to acknowledge such matter in order to obtain reliable results for further implications. This study aims to investigate the detection probability and abundances in these two species as a contribution to the monitoring efforts at a local scale. Night counts were performed in Cedral lagoon located in the Beni region in Bolivia. By using the relation between marked animals and resightings of them, as well as the abundance estimate produced by the Lincoln-Petersen estimator, estimates of detection probabilities could be accounted for the total caiman population (black plus yacare caimans) and the black caiman population. Very low sighting probabilities (p = 0.03) were obtained when based on marked animals who tend to be more wary after a capture event. Those based on the L-P output were higher (total caiman population p = 0.15, black caimans p = 0.15). Population sizes were estimated to 25 ± 8.5 black caimans and 34 ± 12 caimans in total. The population size based on marked animals was 12 ± 25.4 caimans.

The St. Croix ground lizard, Ameiva polops, is a United States endangered species endemic to St. Croix, U.S. Virgin Islands. It was extirpated from St. Croix Proper by invasive mongooses, and remaining populations are on small, nearby cays. In the summer of 2008, as part of the recovery plan for this species, I worked in a multi-agency effort to translocate a population of A. polops to Buck Island Reef National Monument, U.S. Virgin Islands to focus on two main objectives: 1) examine the detection probability of A. polops and infer the consequences of it on population estimates; and 2) examine whether A. polops may deplete its prey base or alter the arthropod assemblage at the translocation site. We used a soft-release strategy for the translocation, in which 57 lizards were initially contained in a series of eight 10 m x 10 m enclosures in the habitat on Buck Island for monitoring. As part of the initial monitoring I conducted visual surveys through all enclosures, with the known number of lizards, to calculate the detection probability and to demonstrate how many individuals would be estimated using visual encounter surveys of this known population. Adjacent to enclosures housing A. polops were control enclosures, without A. polops, which I used to test whether the translocated lizards would impact their prey base over 6 weeks. I found that the detection probability of A. polops is very low (<0.25), which causes population sizes to be severely underestimated, even using some mark-resight techniques. My study of A. polops on the prey community indicated that the lizards generally had no effect on abundance or diversity of arthropods in general, though they may cause small changes for particular taxa. My results help corroborate other evidence that accuracy of population enumeration techniques needs to be improved in order to adequately understand the status of wildlife populations. Additionally, prey resources do not seem to be limiting A. polops in the short-term, and I expect the population will grow, expanding through Buck Island. Future monitoring will be carried out by the National Park Service using robust mark-resight techniques.

Citizen science, which uses volunteer observers in research, is fast becoming standard practice in ecology. In this thesis, I begin with an essay reviewing the benefits and limitations of citizen science, and then measure the influence of several forms of observer error that might bias ornithological citizen science. Using an internet-based survey, I first found that observer skill level can predict the nature of false-positive detections, where self-identified experts tend to falsely detect more rare species and moderately-skilled observers tend to falsely detect more common species. I also found that overconfidence is widespread among all skill levels, and hence that observer confidence is an unreliable indication of data quality. Using existing North American databases, I then found that older observers tend to detect fewer birds than younger observers -- especially if the birds' peak call frequencies exceed 6 kHz -- and that published long-term population trend estimates and high-pitched (>= 6 kHz) peak bird vocalization frequencies are negatively correlated. Taken together, these data suggest that both hearing loss and other sensory changes might be negatively biasing long-term trend estimates. In the next chapter, I measured how observer experience can bias detection data. In solitary observers, I found that detections tend to increase over the first 5 years of service (e.g. learning effects), after which they decline consistently (e.g. observer senescence). Conversely, among survey groups that may be motivated to exceed a previous year's species count, I found that species richness tends to increase consistently with consecutive survey years. In this case, individual sensory deficits may be offset by group participation. Lastly, I re-evaluated the established assumption that the quality of new volunteers on North American Breeding Bird Survey routes is increasing over time. I showed that the existing measure of “quality” ignores variable lengths of observer service, and that, after accounting for this variable, “quality” is unchanging. Throughout this thesis, I also show how generalized additive mixed models can address these biases statistically. My findings offer new opportunities to improve the accuracy and relevance of citizen science, and by extension, the effectiveness of wildlife conservation and management.

Wildlife in urban settings are a management challenge because wildlife populations and their habitats are often fragmented and degraded, but natural resource managers need information concerning their spatial distribution, spatial turnover, and spatial co-occurrence while accounting for imperfect detection. Based in the Chicago Metropolitan Area during 2009-2012, my study modeled 23 species across 5 wildlife taxa concerning patterns of site occupancy, spatial turnover (i.e., colonization and extinction), and/or spatial co-occurrence at 1-2 spatial scales. In detail, I investigated: (1) detection probabilities, site occupancy, and spatial turnover as affected by habitat and anthropogenic influences at 2 spatial scales for 6 species of songbirds: field sparrows (Spizella pusilla), great crested flycatchers (Myiarchus crinitus), willow flycatchers (Empidonax traillii), bobolinks (Dolichonyx oryzivorus), marsh wrens (Cistothorus palustris), and rose-breasted grosbeaks (Pheucticus ludovicianus); (2) detection probabilities, site occupancy, and spatial turnover as affected by habitat and anthropogenic influences at 2 spatial scales for 3 species of reptiles and 4 species of amphibians: common garter snakes (Thamnophis sirtalis), painted turtles (Chrysemys picta), snapping turtles (Chelydra serpentina), blue-spotted salamanders (Ambystoma laterale), tiger salamanders (Ambystoma tigrinum), green frogs (Rana clamitans), and northern leopard frogs (Rana pipiens); (3) habitat use and landscape site occupancy and spatial turnover as affected by habitat and anthropogenic influences for 4 species of mesocarnivores: coyotes (Canis latrans), raccoons (Procyon lotor), striped skunks (Mephitis mephitis), and Virginia opossums (Didelphis virginiana); and (4) detection probabilities and spatial distributions as affected by local habitat, an interacting species (dominant or subordinate), or both for 6 species of small mammals: short-tailed shrews (Blarina brevicauda), meadow voles (Microtus pennsylvanicus), white-footed mice (Peromyscus leucopus), gray squirrels (Sciurus carolinensis), masked shrews (Sorex cinereus), and eastern chipmunks (Tamias striatus). I elucidate how managers can improve or design their survey techniques that will aid their inference of the distribution of wildlife in the Midwest. This work also provides suburban natural resource managers in the Chicago Metropolitan Area with information concerning land management and land acquisition guidelines to best conserve, attract, or deter the aforementioned wildlife on their properties.