Jessi L. Brown

Selection for increased mass-independent maximal metabolic rate suppresses innate but not adaptive immune function

Both appropriate metabolic rates and sufficient immune function are essential for survival. Consequently, eco-immunologists have hypothesized that animals may experience trade-offs between metabolic rates and immune function. Previous work has focused on how basal metabolic rate (BMR) may trade-off with immune function, but maximal metabolic rate (MMR), the upper limit to aerobic activity, might also trade-off with immune function. We used mice artificially selected for high mass-independent MMR to test for trade-offs with immune function. We assessed (i) innate immune function by quantifying cytokine production in response to injection with lipopolysaccharide and (ii) adaptive immune function by measuring antibody production in response to injection with keyhole limpet haemocyanin. Selection for high mass-independent MMR suppressed innate immune function, but not adaptive immune function. However, analyses at the individual level also indicate a negative correlation between MMR and adaptive immune function. By contrast BMR did not affect immune function. Evolutionarily, natural selection may favour increasing MMR to enhance aerobic performance and endurance, but the benefits of high MMR may be offset by impaired immune function. This result could be important in understanding the selective factors acting on the evolution of metabolic rates.

Nest-Site Characteristics Affect Daily Nest-Survival Rates of Northern Aplomado Falcons (Falco Femoralis Septentrionalis)

Abstract We modeled daily nest-survival rates (DSR) of a reintroduced population of Northern Aplomado Falcons (Falco femoralis septentrionalis; hereafter “falcons”) in southern Texas. Although falcons have nested in the region since 1995, the factors influencing reproductive success are not understood. Nest sites were classified into nest-type groups using a cluster analysis based on nest substrate and nest builder. Using an information-theoretic approach, we compared relative effects of nest age, study area, nest-type group, and physical nest-site characteristics. Our results were similar to previous studies of passerine nesting ecology, in that DSR varied throughout the nesting cycle: it was constant during incubation, declined at hatching and the early nestling phase, and increased through the remainder of the nestling phase. Nest type and nest height were important physical nest-site covariates, overhead cover was less important, and study area and nest initiation date were not influential. We note that although nest success was well correlated with simple nest-site covariates, many falcons chose poor-quality nest sites, which raises the question of whether nest-site selection by falcons is optimal in this region. Las Características de los Sitios de Nidificación Afectan las Tasas de Supervivencia Diaria de los Nidos de Falco femoralis septentrionalis

Restoring Aplomado Falcons to the United States

Abstract Captive-bred fledgling Aplomado Falcons (Falco femoralis) were released along the coastal plain of southern Texas (839 birds from 21 sites during 1993–2004) and in the Chihuahuan Desert of western Texas (637 birds from 11 sites in 2002–2011) and southern New Mexico (337 from 10 sites during 2006–2012). The Texas coastal releases yielded two nesting populations: 15–18 pairs near Brownsville and 15 pairs on two islands near Rockport. Habitat in these areas is extensive open savanna, the ancestral condition over most of the region. Today, it is almost entirely dominated by farmland and brushland, the latter harboring the Great Horned Owl (Bubo virginianus), a major predator of the falcons. Conversely, releases in the Chihuahuan Desert have been unsuccessful in establishing a wild population in either area. Although 8–10 pairs were present in West Texas in 2009, by 2011 only one pair remained, and none were found in 2012, the apparent consequence of severe drought. A single pair documented in New Mexico in 2011 was associated with artificial feeding of prey birds. We concluded that the conservation and expansion of Aplomado Falcon populations on the Texas coastal plain will require the protection and management of existing breeding territories, and the creation and management of more brush-free savanna. Persistent drought, the reduction of prey populations, and high rates of mortality from raptor predation appear to preclude the reestablishment of Aplomado Falcons in western Texas or New Mexico. DEVOLVIENDO A FALCO FEMORALIS A LOS ESTADOS UNIDOS Se liberaron volantones de Falco femoralis criados en cautiverio a lo largo de las planicies costeras del sur de Texas (839 aves de 21 sitios durante 1993–2004) y en el desierto de Chihuahua del oeste de Texas (637 aves de 11 sitios durante 2002–2011) y del sur de Nuevo México (337 aves de 10 sitios durante 2006–2012). Las liberaciones en la costa de Texas produjeron dos poblaciones que anidaron: 15–18 pares cerca de Brownsville y 15 pares en dos islas cerca de Rockport. El hábitat de esta área se compone de una extensa sabana abierta, lo que representa la condición ancestral de casi toda la región. Actualmente se encuentra casi completamente dominada por tierras de labranza y matorrales; este último alberga a Bubo virginianus, uno de los mayores depredadores de halcones. Por el contrario, las liberaciones en el desierto de Chihuahua no fueron exitosas en el establecimiento de poblaciones silvestres. Aunque se encontraron 8–10 pares en el oeste de Texas en 2009, para el 2011 sólo se registró un par y no se encontró ninguno en 2012, como consecuencia aparente de una sequía severa. Una sola pareja documentada en Nuevo México en 2011 estuvo asociada con la alimentación artificial de aves de presa. Concluimos que la conservación y la expansión de poblaciones de F. femoralis en las planicies costeras de Texas requerirán de la protección y el manejo de los territorios de cría existentes, y de la creación y manejo de sabanas libres de matorrales. La sequía persistente, la reducción de las poblaciones de presas y las altas tasas de mortalidad debidas a la depredación por parte de rapaces parecen impedir el restablecimiento de poblaciones de F. femoralis en el oeste de Texas o Nuevo México.

PIRACY AS AN IMPORTANT FORAGING METHOD OF APLOMADO FALCONS IN SOUTHERN TEXAS AND NORTHERN MEXICO

Abstract Piracy (kleptoparasitism) accounted for 14% of observed foraging attempts on vertebrates (n = 125) by Aplomado Falcons (Falco femoralis) in southern Texas and northern Mexico, and was over twice as successful as hunting (82% versus 37%). Aplomado Falcons pirated prey cooperatively as well as individually. Eight bird species were targeted for piracy, six of which were as large or larger than the falcons. The majority of prey items stolen were mammals.

Coming to Terms About Describing Golden Eagle Reproduction

Abstract Clearly defined terms are essential for reporting and understanding research findings, and inconsistent terminology can complicate efforts to compare findings from different studies. In this article, we reiterate and clarify recommended terms for describing Golden Eagle (Aquila chrysaetos) territory occupancy and reproduction. Several authors have provided recommendations for reporting data on raptor reproduction, but our literature review showed that authors continue to use different, often ambiguous and undefined, terms. The inconsistent use of terminology by researchers has been continued and expanded by lawmakers, regulators, and managers, perpetuating confusion. We recommend that authors clearly define and reference all terminology that they use, and we caution against use of the term “active” to describe a nest or nesting territory, because it is tainted with a history of inconsistent use. We provide a glossary of recommended terms for Golden Eagles and other large, long-lived raptors.

Habitat fragmentation reduces occupancy of nest boxes by an open-country raptor

Despite the recent rapid decline of many grassland bird species, the relative importance of habitat configuration to population persistence is unclear. We used Southeastern American Kestrels Falco sparverius paulus in north-central Florida as a model system to explore the relative influence of landscape structure components on site occupancy patterns at two spatial scales, and for two different time periods. We focused on the dynamic processes of site-level population expansion or contraction. We modelled the occupancy of 131 American Kestrel nest boxes with Bayesian state-space dynamic occupancy models that considered both the partially observed process of true occupancy and the probability of detection of occupancy. We used reversible jump Markov chain Monte Carlo (RJMCMC) algorithms to identify variables that described the continued occupancy of nest boxes, or ϕ, and the probability of colonisation of nest boxes between time periods, or γ 3 . Changes in open habitat patch isolation at a fine scale, as estimated by the variability of nearest neighbour distance, predicted site colonisation between decades, and patch shape variability was related to ϕ during the early time period (1992–93). We found no strong effects of landscape structure on ϕ during the later time period (2008–2010). We also found no evidence for effects of loss of open habitat on box occupancy or colonization. Our results indicate that continued habitat fragmentation would be deleterious for this threatened subspecies. Additionally, certain land cover management practices recommended for the Florida sandhills, such as frequent low-intensity controlled burns, will likely help conservation attempts.

Speeding up Growth: Selection for Mass-Independent Maximal Metabolic Rate Alters Growth Rates

Investigations into relationships between life-history traits, such as growth rate and energy metabolism, typically focus on basal metabolic rate (BMR). In contrast, investigators rarely examine maximal metabolic rate (MMR) as a relevant metric of energy metabolism, even though it indicates the maximal capacity to metabolize energy aerobically, and hence it might also be important in trade-offs. We studied the relationship between energy metabolism and growth in mice (Mus musculus domesticus Linnaeus) selected for high mass-independent metabolic rates. Selection for high mass-independent MMR increased maximal growth rate, increased body mass at 20 weeks of age, and generally altered growth patterns in both male and female mice. In contrast, there was little evidence that the correlated response in mass-adjusted BMR altered growth patterns. The relationship between mass-adjusted MMR and growth rate indicates that MMR is an important mediator of life histories. Studies investigating associations between energy metabolism and life histories should consider MMR because it is potentially as important in understanding life history as BMR.

Raptor nesting locations along an urban density gradient in the Great Basin, USA

Raptors are the most prevalent group of urban apex predators, and the majority of raptor genera in North America have been recorded using urban areas. Prior research assessments along urban-wildland gradients show that urban habitat preference varies by raptor species and that raptor nesting preferences within urban settings may vary. Attempts to understand the intra- and inter-specific nesting patterns along an urban gradient would advance extant knowledge. Here we present the locations of individual nest sites of nine raptor species along an urban gradient in Reno-Sparks, NV. We developed an urban density model based on the number of residents, number of employees, and building footprints and number of floors for built structures within each land parcel at four spatial scales, representing nest site, macrohabitat, average nearest-nest, and landscape scales. Cooper’s Hawks (Accipiter cooperii), Sharp-shinned Hawks (Accipiter striatus), and Red-tailed Hawks (Buteo jamaicensis) nested across the widest range of the urban spectrum and closest to the urban core, whereas Golden Eagles (Aquila chrysaetos) and Swainson’s Hawks (Buteo swainsonii) nested on the urban fringe. Urban density for all nest locations was lowest at the nest-site scale, and the highest at the average nearest-nest and landscape scales. Raptors tended to occupy a wide range of the building-area density spectrum but not the building-height or employee density spectrums indicative of the attractiveness of suburban habitat.

Golden Eagles in a Changing World

In recent years, Golden Eagles (Aquila chrysaetos) have emerged as a conservation concern in the United States, particularly in the West. Our nation’s effort to become more energy independent has involved a significant expansion in the development of domestic sources of both renewable and nonrenewable energy. The influence of energy development, particularly wind energy, taken together with other anthropogenic sources of mortality, including electrocution on power distribution lines, contaminants, collisions with vehicles, and illegal shooting, may be resulting in declining Golden Eagle populations (U.S. Fish and Wildlife Service [U.S.F.W.S.] 2016a). To achieve the objective of ‘‘stable or increasing breeding populations’’ promulgated under the Bald and Golden Eagle Protection Act (Eagle Act; 16 U.S.C. 668-668d) and appurtenant regulations (U.S.F.W.S. 2009, 2016b; hereafter Eagle Rule), the U.S.F.W.S. will require a greater understanding of Golden Eagle population dynamics, movement patterns, and genetic connectivity across populations, and conservation practices that reliably reduce or mitigate population limiting factors (U.S.F.W.S. 2016a, 2016b). In addition, state, federal, and tribal wildlife and land management agencies need this information to support conservation planning for Golden Eagles at local and regional scales. To support the dissemination of new information on the demography, nesting ecology, movement patterns, diet, and conservation of Golden Eagles, the Academy for the Environment, University of Nevada, Reno, and Western Golden Eagle Team, U.S. Fish and Wildlife Service, collaborated to host a symposium at the 2015 annual conference of the Raptor Research Foundation (RRF), in Sacramento, California. Invited speakers presented new information during three sessions that focused specifically on Golden Eagle demography and population trends, use of innovative research technologies and techniques, and conservation planning. Six of the presenters subsequently developed manuscripts published in this special issue. The California–Nevada Golden Eagle Working Group convened a meeting immediately prior to the RRF meeting in Sacramento, where they hosted a symposium that focused on Golden Eagle prey ecology and the need for using consistent terminology in raptor ecology. Two of the invited presenters subsequently developed manuscripts that also appear in this special issue; one of these discusses the use of terminology in describing reproduction, the other summarizes spatial and temporal patterns in eagle diets throughout the western U.S.A. Four additional manuscripts, not associated with these symposia, are also included in this special issue, since they address issues highly relevant to Golden Eagle conservation and management. These papers address several different topics, including

Patterns of Spatial Distribution of Golden Eagles Across North America: How Do They Fit into Existing Landscape-scale Mapping Systems?

Abstract Conserving wide-ranging animals requires knowledge about their year-round movements and resource use. Golden Eagles (Aquila chrysaetos) exhibit a wide range of movement patterns across North America. We combined tracking data from 571 Golden Eagles from multiple independent satellite-telemetry projects from North America to provide a comprehensive look at the magnitude and extent of these movements on a continental scale. We compared patterns of use relative to four alternative administrative and ecological mapping systems, namely Bird Conservation Regions (BCRs), U.S. administrative migratory bird flyways, Migratory Bird Joint Ventures, and Landscape Conservation Cooperatives. Our analyses suggested that eagles initially captured in eastern North America used space differently than those captured in western North America. Other groups of eagles that exhibited distinct patterns in space use included long-distance migrants from northern latitudes, and southwestern and Californian desert residents. There were also several groupings of eagles in the Intermountain West. Using this collaborative approach, we have identified large-scale movement patterns that may not have been possible with individual studies. These results will support landscape-scale conservation measures for Golden Eagles across North America.