Browsing by Author "Doherty, Paul F., Jr., advisor"

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Open Access
Avian conservation and ecology in northern Vietnam
(Colorado State University. Libraries, 2009) Vu, Thinh Tien, author; Doherty, Paul F., Jr., advisor; Huyvaert, Kathryn, advisor
Due to the rapid rate of biodiversity loss in Vietnam conserving the avian biodiversity is a contemporary issue of concern and my dissertation was aimed at several issues focused on avian conservation. Recently, the number of non-native tree plantations has increased but the conservation potential of such plantations remains unknown. In Chapter 1, I estimated bird species richness to be highest in mature natural forest, lower in second-growth natural forest, and lowest in pine plantation. I suggest that natural forest types should receive priority for conservation in Vietnam. In Chapter 2, I compared bird movement over a paved road (6-8m wide) and within forest interior plots. The probabilities of approaching the playback for ground species at the road site were lower than those in the forest interior. The road seems to moderately affect the ability for ground-feeding bird species to cross gaps. Roads in the natural reserves should be designed to be as narrow as possible. In Chapter 3, to investigate the effects of logging on biodiversity, I modeled the recovery of avian communities following a variety of potential logging schemes. I found that, to conserve 80% of the species pool, logging schemes with either cycle length > 40 years or wood volume left after harvest > 55% should be implemented. Wildlife diseases are raising concerns with respect to human and domestic animal health, as well as the persistence of wildlife populations. Chapter 4 was aimed at characterizing the sample prevalence of avian malaria in wild land birds. The prevalence of avian malaria was 45.85%. However, higher parasite prevalence was observed in flocking species compared to solitary species and higher parasite prevalence was observed in adult birds compared to juvenile birds. In Chapter 5, I focused on surveillance for the presence of avian influenza virus nucleic acids and antibodies in wild land birds. Serum samples from four birds out of 197 birds sampled were antibody positive for the H5 subtype. Sample prevalence for avian influenza virus nucleic acids was 7.25%. This result suggests that attention should be given to land birds in AI surveillance and monitoring programs.
Open Access
Calcium, telomere length, and parasitism in passerines nesting at high elevation
(Colorado State University. Libraries, 2020) Rodriguez, Marina D., author; Huyvaert, Kathryn P., advisor; Doherty, Paul F., Jr., advisor; Bailey, Susan M., committee member
Most organisms are exposed to numerous environmental stressors at various points throughout life, and, through natural selection, organisms' responses to such stressors have been optimized by natural selection for the best fitness outcomes. During the breeding season, wild vertebrates often make a trade-off between current reproduction and self-maintenance when dealing with environmental stressors. The total cost of reproduction is made up of all of the resources and energy that go into activities related to reproduction (e.g., nest building, finding a mate, foraging for food and nutrients related to offspring production, parental care) that do not go into self-maintenance. The cost of these activities can vary depending on resource availability, where limited resources can increase the cost associated with breeding due to increased energy associated with foraging and competing for the resource. In birds, calcium is a critical resource due to its importance in egg production and offspring development, and low calcium availability often leads to decreased reproductive success. In my first chapter, I used an experimental approach to assess the effects of supplemental calcium on reproductive parameters of Tree Swallows (Tachycineta bicolor) in a high elevation environment. Calcium-supplemented birds in my study area laid more, larger eggs, and had higher hatching success compared to control females. These results provide evidence that calcium availability is a constraint on breeding Tree Swallows at high elevation, perhaps due to the harsh conditions and concomitantly higher metabolic costs that force a costlier and more intense trade-off between foraging for food or for calcium. The increase in reproductive parameters for calcium supplemented nests in Chapter 1 highlights a cost associated with calcium foraging that constrains reproduction. For my second chapter, I aimed to better understand how calcium availability affects the cost of reproduction in mother Tree Swallows and offspring by using telomere shortening as a proxy of life stress and lifespan. Telomeres are terminal features of chromosomes consisting of repetitive DNA sequences that shorten with age and stress, and whose length is positively correlated with survival. I used telomere shortening as a proxy for the costs associated with reproduction to better understand life history trade-offs of Tree Swallows at high elevation sites. Similar to Chapter 1, I found that Tree Swallows supplemented with calcium had higher reproductive success, although I also found that supplemented nests had more telomere shortening compared to birds at control nests. These results provide evidence that Tree Swallows supplemented with calcium experience higher reproductive output at the cost of lower expected survival in the form of more telomere shortening. While investing resources in reproduction may lead to higher reproductive output for the current breeding season, this increase in reproductive success can come with a cost to survivorship. One way that resource allocation can shape survivorship is through investment in immune function. In many systems, however, more species-level and individual-level research is needed on host-parasite relationships before trade-offs between immune function and reproduction can be assessed. For my third chapter, I conducted a survey of avian Haemosporida: blood parasites that include those that cause avian malaria. I surveyed an avian community for haemosporidian parasites in the Colorado Rocky Mountains in order to estimate prevalence and diversity of blood parasites and to find species-level and individual-level characteristics that influence infection prevalence. I found that open cup nesters have higher blood parasite prevalence than cavity or open cup nesters. Additionally, male Ruby-crowned Kinglets, White-crowned Sparrows, and Wilson's Warblers had a higher prevalence of haemosporidian parasites compared to the other species analyzed, as did Red-breasted Nuthatches, which, like Ruby-crowned Kinglets, have a high body condition index. This chapter presents baseline knowledge of avian blood parasite presence, prevalence, and diversity across avian species in the Colorado Rocky Mountains and adds to our knowledge of host-parasite relationships of blood parasites and their avian hosts.
Open Access
Reproductive success, habitat selection, and neonatal mule deer mortality in a natural gas development area
(Colorado State University. Libraries, 2016) Peterson, Mark E., author; Doherty, Paul F., Jr., advisor; Anderson, Charles R., Jr., committee member; Meiman, Paul, committee member; Wittemyer, George, committee member
Mule deer (Odocoileus hemionus) populations have periodically declined throughout the western United States, with notable declines during the late 1960s, early 1970s, and 1990s (Unsworth et al. 1999) to present. Declining population levels can be attributed to low fawn survival and subsequently low population recruitment (Unsworth et al. 1999, Pojar and Bowden 2004) caused by declining habitat availability and quality (Gill 2001, Lutz et al. 2003, Watkins et al. 2007, Bergman et al. 2015). Although, general public perception is that declining deer numbers are attributed exclusively to predation (Barsness 1998, Willoughby 2012), predator control research suggests otherwise (Hurley et al. 2011, Kilgo et al. 2014) and compelling evidence exists that improving habitat quality can enhance deer populations (Bishop et al. 2009, Bergman et al. 2014). Complicating this story is the large-scale habitat alterations driven by natural gas development, which may also influence deer population dynamics. Natural gas development and associated disturbances that can affect deer habitat and population dynamics include conversion of native plant communities to drill pads, roads, or noxious weeds and noise pollution from compressor stations, drilling rigs, increased traffic, and year round occurrence of human activities. Natural gas development alters mule deer habitat selection through direct and indirect habitat loss (Sawyer et al. 2006, Sawyer et al. 2009, Northrup et al. 2015). Direct habitat loss results from construction of well pads, access roads, compressor stations, pipelines, and transmission lines. Activity, traffic, and noise associated with increased human presence and development may lead to indirect habitat loss. Indirect habitat loss is exacerbated because active wells produce gas for 40 years or longer (Sawyer et al. 2006, Sawyer et al. 2009). In addition, indirect habitat loss affects considerably larger areas than direct habitat loss (Sawyer et al. 2006, Sawyer et al. 2009). Recent research suggests direct and indirect losses can lead to behavioral responses to development (Sawyer et al. 2006, Dzialak et al. 2011b, Northrup et al. 2015). However, deer can behaviorally mediate these impacts by altering activity patterns or selecting habitat with topographic diversity that provides refuge from development (Northrup et al. 2015). Obtaining a more complete understanding of the potential impacts of development is critical to comprehend population dynamics of deer and to develop viable mitigation options. Understanding how natural gas development and other factors influence reproductive success metrics (e.g., pregnancy, in utero fetal, and fetal survival rates), fetal sex ratio, habitat characteristics of birth and predation sites (i.e., habitat selection), and neonatal (i.e., 0–6 months old) mule deer mortality have been identified as knowledge gaps. Thus, my dissertation focused on addressing these knowledge gaps through individual reproductive success monitoring using vaginal implant transmitters. I conducted this research during 2012–2014 in the Piceance Basin of northwestern Colorado in study areas with relatively high (0.04–0.90 well pads/km2) or low (0.00–0.10 well pads/km2) levels of natural gas development. In chapter 1, I examined the influence of adult female, natural gas development, and temporal factors on reproductive success metrics (i.e., pregnancy rate, in utero fetal rate, and fetal survival rate) and fetal sex ratio. Pregnancy rates were high, did not vary across years, and were essentially equal between study areas. In utero fetal rates were lower for yearling females (n = 10) and varied annually compared to adult females (n = 204) possibly from annual weather patterns that influenced forage quality and digestibility. Fetal survival rates increased over time and were lower in the high development study areas than the low development study area in 2012 possibly caused by a compounding influence of development disturbance during extreme environmental conditions (i.e., drought). Higher road density in a female’s core area (i.e., 50% minimum convex polygon) on summer range possibly contributed to better maternal body condition through increased forage quality along roads. Following the Trivers-Willard hypothesis which predicts females in good versus poor condition will produce more males, my results suggested females had a higher probability of producing more male offspring as road density increased. However, under my proposed mechanism, I would expect body condition and road density to be strongly correlated, but they were only weakly correlated (r = 0.07). I also note that I did not detect a biased sex ratio at the population level. Thus, I am uncertain of the exact mechanism influencing the relationship between road density and fetal sex ratio. In chapter 2, I used global positioning system collar data in conjunction with VITs and linear mixed models to validate the use of maternal deer movement rates (m/day) to determine timing of parturition. Daily movement rate of maternal deer decreased by 39% from 1 day before parturition ((x ) ̅ = 1,243.56, SD = 1,043.03) to 1 day after parturition ((x ) ̅ = 805.30, SD = 652.91). Thus, I suggest that a mule deer female whose daily movement rate significantly decreases to ≤ 800 m/day has likely given birth. In the future, I will analyze an independent data set to validate the recommended threshold value and possibly develop a movement rate algorithm. In chapter 3, I fit resource selection functions to examine the influence of natural gas development and environmental factors on birth site selection and habitat characteristics of predation sites. Females selected birth sites farther from producing well pads and with increased cover for concealing neonates and appeared to select habitat (e.g., north-facing slopes and further from treed edges) that minimized neonate predation risk. Predation sites were characterized as being closer to development and in habitat (e.g., woodlands, aspen-conifer stands, and north-facing slopes) that possibly provided favorable microclimates for neonates and abundant high quality forage for lactating females. However, I note that predation sites were on average relatively far (2,057 m) from producing well pads and I have difficulty proposing a mechanism to explain how well pads that far away can influence predation site characteristics. My results suggest natural gas development and environmental factors (e.g., slope, habitat type, and aspect) can influence birth site selection with predation site characteristics possibly related to foraging habitat selection. In chapter 4, I tested hypotheses about the influence of adult female, natural gas development, neonate, and temporal factors on neonatal mortality using a multi-state model. Predation and death by malnutrition decreased from 0–14 days old. Predation of neonates was positively correlated with rump fat thickness of adult females, but negatively correlated with the distance (0–0.4 km) from a female’s core area (i.e., 50% kernel density estimate) to a producing well pad on winter or summer range. Death by malnutrition was positively correlated with the distance from a female’s core area to a road on winter range and weakly, but negatively correlated with temperature. During my study, predation was the leading cause of neonatal mortality in both areas and mean daily predation probability was 9% higher in the high versus low development areas. However, black bear (Ursus americanus) predation was the leading cause of neonatal mortality in the high development areas (22% of all mortalities) compared to cougar (Felis concolor) predation in the low development areas (36% of all mortalities). Reduced precipitation and patchy habitat further fragmented by development possibly contributed to less hiding cover or edge effects, potentially leading to increased predation in the high development areas. Overall, my results suggest natural gas development may decrease fetal survival, influence birth site selection, and increase neonatal mortality, especially through predation, which may have consequences for mule deer recruitment and population dynamics depending on development intensity, habitat, and environmental conditions (e.g., drought). Consequently, developers and managers should consider strategies to mitigate impacts from development and improve forage and habitat quality and availability to minimize fitness consequences of deer. Such strategies could include development planning to avoid important habitats during critical time periods, implementing habitat treatments to rehabilitate areas, and minimizing habitat fragmentation and removal of hiding cover when constructing well pads and roads.
Open Access
Restoration of scaled quail to historic ranges in the Rolling Plains ecoregion of Texas
(Colorado State University. Libraries, 2024) Ruzicka, Rebekah Elizabeth, author; Doherty, Paul F., Jr., advisor; Rollins, Dale, committee member; Kendall, William L., committee member; Otis, David L., committee member; Webb, Colleen T., committee member
Scaled quail (Callipepla squamata) are a gallinaceous game bird native to the grasslands and deserts of the southwestern United States and northcentral Mexico experiencing range contraction and population decline due to habitat fragmentation and degradation. Once abundant in the Rolling Plains ecoregion of Texas dating back to the 1880's, scaled quail were locally extinct throughout most of the ecoregion by the late 1980's primarily due to brush encroachment and spatial aggregation of row crop agriculture. Despite state and federal landowner habitat restoration programs (e.g., Landowner Incentive Program, Environmental Quality Incentives Program) scaled quail populations in the Rolling Plains ecoregion failed to respond, likely because the same fragmentation that contributed to decline also prevented effective natural recolonization to restored habitats. Translocation of wild-caught quails to reestablish self-sustaining populations gained popularity during the 2000's, particularly due to success reestablishing northern bobwhites (Colinus virginianus) in fragmented habitats of the southeastern United States. However, many translocations in arid, western climates were either poorly documented or failed outright. Understanding factors that influence translocation outcomes and form best practices is critical for translocation to be used effectively as a management tool. I examined long-term, seasonal survival in a population of scaled quail successfully reestablished on the Rolling Plains Quail Research Ranch in Fisher County, Texas in the context of drought and demographics (Chapter 1). Competing hypotheses predict that scaled quail populations are either resistant to drought or that annual survival is negatively correlated with precipitation amounts. My findings supported the hypothesis that scaled quail are drought sensitive. Additionally, I found survival was lower during non-breeding season, for females, and adults. Scaled quail survival estimates reported here are the most comprehensive for the species and the longest-term study of a translocated scaled quail population to date. I conducted a field experiment to test the effects of source population and variation in delayed release strategy (1–9 weeks) on mortality, dispersal, nest initiation, renesting rate, and nest survival of wild-caught, translocated scaled quail (Chapters 2 and 3). I trapped and translocated quail over 2 years (2016–2017) from source populations in the Edwards Plateau and Rolling Plains ecoregions to a large (>40,000 ha), contiguous release site in Knox County, Texas. Data were analyzed using two multi-state mark-recapture models with state uncertainty to incorporate uncertainty in the process of observing location and nest initiation in radio-marked birds. The framework I used to model reproductive processes is a novel method for obtaining estimates of nest initiation and renesting rate (Chapter 3). I found that scaled quail translocated within the Rolling Plains were more likely to exhibit philopatry to the release site, but that source population did not influence reproduction. Quail with longer holding times had higher mortality, but lower dispersal rates. Additionally, increased length of holding time decreased renesting effort. Yearlings were more likely to initiate nests than adults and the probability of renesting was lower during drought conditions. Finally, I compiled estimated demographics from chapters 1–3 to inform a matrix population model (MPM) that compared asymptotic and transient dynamics under wet and drought conditions (Chapter 4). While traditional MPM analyses focus on asymptotic dynamics, transient dynamics are more relevant for modeling short-term dynamics in translocated or unstable populations. My findings showed divergence between transient and asymptotic dynamics, with asymptotic projections potentially overestimating population growth by 14%. Asymptotic growth rates were most sensitive to renesting rate changes, while transient growth rates were affected by changes in hatchability and renesting rates. The results from my research will inform management decisions and I summarize my recommendations in Chapter 5. I suggest managers avoid initiating translocations in years projected to have drought conditions. Improved accuracy of El Nino–Southern Oscillation cycle-based long-range forecasts has made predictions a useful tool for managers considering translocation. Even so, translocated populations can persist long-term in drought conditions despite the negative impacts to survival and reproduction. Longer holding times for translocated scaled quail result in lower dispersal but higher mortality and lower renesting rates, presenting a decision tradeoff for managers. Managers can hold scaled quail on the release site (up to 9 weeks) when limiting dispersal is a priority (e.g., when in habitats surrounded by a high degree of fragmentation) or holding birds makes the translocation more feasible. However, when considering all factors a holding time of 2–3 weeks is ideal (Chapter 5). The Edwards Plateau is a suitable source site for translocations in the Rolling Plains. Managers should consider transient dynamics when modeling populations where short-term outcomes are relevant such as translocation. By doing so, I show that prioritizing the translocation of yearlings, the stage class with the highest reproductive value, can result in a 16% larger population after one year compared to translocating only adults.
Open Access
Shorebird habitat use and abundance estimates on military lands in interior Alaska
(Colorado State University. Libraries, 2019) Martin, Ellen C., author; Doherty, Paul F., Jr., advisor; Bagley, Calvin F., committee member; Jochum, Kim A., committee member; Kendall, William L., committee member; Shockley, Kenneth, committee member
To view the abstract, please see the full text of the document.