bluuebunny/crossref_metadata_2025 huggingface dataset:
Geographical Structure of Genetic Variation in the Malagasy Scops-Owl Inferred from Mitochondrial Sequence Data
Authors: Fuchs JÉRÔME , Pons Jean-Marc , Pasquet Eric. , Jeanne Raherilalao Marie , Goodman Steven M
Published: September 2019

A recent taxonomic revision of the Malagasy Scops-Owl (Otus rutilus) recognized two distinct endemic species on the island based on plumage, vocal, and morphological characters: O. rutilus (sensu stricto) from eastern humid forest formations and O. madagascariensis from western dry forest areas. An evaluation of these characters calls into question their validity for taxonomic studies, as they may be ecologically linked. To independently assess the two-species hypothesis, we used sequence data from 1449 base pairs (bp) of mitochondrial DNA (mtDNA) from 34 scops-owls obtained across the range of these two putative species. Nineteen haplotypes were detected, four of which were shared by more than one individual. Maximum sequence divergence was 0.6% (mean  =  0.24%). While the most common haplotype was shared by 10 individuals originating from different eastern and western localities, 12 haplotypes were exclusive to O. rutilus and five to O. madagascariensis. An analysis of molecular variance showed significant partitioning of the genetic variability between O. rutilus and O. madagascariensis. The estimate of the divergence time between populations associated with the names O. rutilus and O. madagascariensis was 8070 years BP. Based on haplotype frequencies and sequence divergence, we conclude that there are two populations of Otus on Madagascar that started to diverge in recent geological time following an ecological parapatric model, perhaps associated with Quaternary climatic shifts. Using these results, it is inappropriate to recognize two species of Otus on Madagascar.
Geographic Variation in Color, Measurements, and Molt of the Lesser Goldfinch in North America Does not Support Subspecific Designation
Authors: Willoughby Ernest J.
Published: September 2019

I examined 963 study skins of Lesser Goldfinches (Carduelis psaltria) from the United States to central Mexico, for color, measurements, molt, and plumage wear. These specimens had been previously assigned to as many as three subspecies. Females did not vary geographically in color. Green-backed, green-eared males predominated in the Pacific coastal United States and northern Mexico. Black-backed, black-eared males predominated in the interior, east of 106° West longitude. This west to east color difference varied clinally, and may be a simple genetic polymorphism, so subspecific distinctions cannot be justified by coloration alone. Measurements of bill, tail, and wing, but not tarsus, varied slightly but significantly from smallest along the Pacific coast to largest in south-central Mexico. Since measurements varied clinally, and overlapped extensively, subspecific separation based on size is not practical. Pacific coastal birds subjected to winter rainfall maxima had a complete postbreeding molt, with a sparse prebreeding body molt only in females, and a postjuvenal molt that replaced significantly more flight feathers in males. Interior birds subjected to summer precipitation maxima had a nearly complete or complete prebreeding molt and a usually less complete postbreeding molt. The postjuvenal and postbreeding molts of interior birds were very similar and did not differ between the sexes. Although these sexual and geographic variations of molt are striking, they may reflect phenotypic plasticity in response to environmental contingencies, rather than genetic differences. These variations in one intergrading population support doubts that the Humphrey-Parkes terminology for molts and plumages can reflect phylogenetic homologies among species.
Potential Effects of Climate Change on Elevational Distributions of Tropical Birds in Southeast Asia
Authors: Peh Kelvin S-H.
Published: September 2019

An analysis of the elevational distributions of Southeast Asian birds over a 28-year period provides evidence for a potential upward shift for 94 common resident species. These species might have shifted their lower, upper, or both lower and upper boundaries toward a higher elevation in response to climate warming. These upward shifts occurred regardless of habitat specificity, further implicating climate warming, in addition to habitat loss, as a potentially important factor affecting the already imperiled biotas of Southeast Asia.
Intraspecific Latitudinal Variation in Nest Orientation Among Ground-Nesting Passerines: A Study Using Published Data
Authors: Burton Niall H.K.
Published: September 2019

The relationship between nest entrance orientation and latitude among ground-nesting passerines was reviewed using published information. Data were collated for seven North American and European species. Pooling within-species comparisons, there was a clear trend from a preference for north-facing nests at lower latitudes to eastward- or southward-facing nests farther north. Orientations differed significantly in eight of 12 cases for which statistical comparison was possible, means differing in the expected direction in six of these cases. These results highlight how the influence of solar radiation on nest microclimate typically delineates preferred nest orientation in these species, i.e., at lower latitudes, the need for shade results in a preference for northward orientations; at mid latitudes, eastward orientations predominate, reflecting a probable balance between the benefits of warmth in the early morning and shade in the afternoon; while at high latitudes, nests may be oriented southward to gain warmth throughout the day.
Heat Production From Foraging Activity Contributes to Thermoregulation in Black-Capped Chickadees
Authors: Cooper Sheldon J. , Sonsthagen Sarah
Published: September 2019

We measured metabolic heat production (H ˙m) of perching and foraging Black-capped Chickadees (Poecile atricapillus) to determine if the heat produced during foraging activity, or exercise thermogenesis, could replace thermoregulatory heat production requirements. H ˙m and activity of chickadees in winter were measured at ambient temperatures (Ta) ranging from −11.5° to 15.5°C. Mean activity amplitude recorded with an activity detector was significantly higher in foraging birds than perching birds. H ˙m did not vary significantly between perching and foraging birds, indicating that heat produced during foraging does substitute for heat produced by shivering for thermoregulation. Evaporative water loss and dry thermal conductance did not vary significantly between perching and foraging chickadees. These results suggest that heat produced from locomotor muscles during foraging activity substitutes for thermoregulatory requirements in glean-and-hang foraging species, such as chickadees, as well as in ground-foraging birds.
Habitat Selection in a Changing Environment: The Relationship Between Habitat Alteration and Spotted Owl Territory Occupancy and Breeding Dispersal
Authors: Seamans Mark E. , Gutiérrez R.J.
Published: September 2019

Abstract. Understanding the effect of habitat alteration on avian behavior is important for understanding a species' ecology and ensuring its conservation. Therefore, we examined the relationship between Spotted Owl habitat selection and variation in habitat in the Sierra Nevada. We estimated habitat selection by modeling the probability of territory colonization (γ), territory extinction (ε), and breeding dispersal in relation to the amount of mature conifer forest within and among territories. Alteration of ≥20 ha of mature conifer forest (coniferous forest with >70% canopy cover dominated by medium [30.4–60.9 cm dbh] and large [>60.9 cm dbh] trees) within individual territories (n  =  66) was negatively related to territory colonization and positively related to breeding dispersal probability. Although territory extinction was negatively related to the amount of mature conifer forest, it was not clear whether this relationship was due to variation of mature conifer forest within or among territories. Although modeling results for territory colonization and extinction generally supported the hypothesis that individuals are “ideal” when selecting a habitat in the sense that they settle in the highest-quality site available, we did not find a clear benefit in terms of habitat quality for Spotted Owls that exhibited breeding dispersal.
Sexual Dichromatism, Dimorphism, and Condition-Dependent Coloration in Blue-Tailed Bee-Eaters
Authors: Siefferman Lynn , Wang Yuan-Jyun , Wang Yi-Ping , Yuan Hsiao-Wei
Published: September 2019

Abstract. The Blue-tailed Bee-eater (Merops philippinus) is a cooperatively breeding and socially monogamous member of the Coraciiformes that displays conspicuous coloration and elongated central rectrices (“streamers”). Humans cannot distinguish males from females; both sexes are brightly colored with a chestnut throat patch, a yellow chin, and green body coloration fading into a turquoise-blue rump and tail. We quantified coloration with ultraviolet- (UV) visible spectrometry and measured morphology to determine the extent of sexual dichromatism and dimorphism. Males displayed more exaggerated coloration, longer tail streamers, and were larger than females. Multiple plumage ornaments (measures of plumage coloration and streamer length) were positively correlated in both sexes. Males in better body condition expressed darker chestnut throats and more chromatic green body plumage. Females in better body condition, however, exhibited more chromatic blue rumps and yellow chins. This study represents the first objective description of plumage ornamentation in the order Coraciiformes.
Color Differences Among Closely Related Species of Red-Breasted Meadowlarks (Sturnella)
Authors: Benites Pilar , Tubaro Pablo L. , Lijtmaer Darío A. , Lougheed Stephen C. , Eaton Muir D.
Published: September 2019

Abstract. Interspecific differences in sexually selected traits may be important for maintaining reproductive isolation among closely related species living in sympatry. We present the first study of plumage color differences among males of partially sympatric species of South American red-breasted meadowlarks—the White-browed Blackbird (Sturnella superciliaris), the Pampas Meadowlark (S. defilippii), and the Long-tailed Meadowlark (S. loyca)—using reflectance spectrophotometry and the avian visual model of Vorobyev and Osorio (1998). Reflectance values of sexually dichromatic red plumage patches were measured on study skins. Total reflectance, reflectance in the short wavelength part of the spectrum, and several measures of spectral shape were extracted directly from the spectra. Our analyses revealed that S. loyca and S. defilippii were brighter and had higher reflectance in the short wavelength part of the spectrum than S. superciliaris. Minimum reflectance was located at higher wavelengths in breeding than in nonbreeding plumage. Interspecific distances in avian visual space obtained from the Vorobyev and Osorio (1998) model were considerably higher than the threshold value for color discrimination, indicating that the differences found are also detectable by birds. Taken together, these results show that the red plumage patches of these three species present significant color differences throughout the year, not only in the visible but also in the UV part of the spectrum.
Forest Edges Negatively Affect Golden-Cheeked Warbler Nest Survival
Authors: Peak Rebecca G.
Published: September 2019

Abstract. I used an information-theoretic approach to determine support for hypotheses concerning the effects of edge and temporal factors on Golden-cheeked Warbler (Dendroica chrysoparia) nest survival on Fort Hood Military Reservation, Texas, during 2003–2006. I predicted that nest survival would be greater earlier in the breeding season than later in the breeding season, in areas with less forest edge than in areas with more forest edge, and during the laying and incubation stages than during the nestling stage. I used the logistic-exposure method to model nest survival as a function of the explanatory variables and to produce model-based estimates of daily and period survival. The overall daily survival rate was 0.96 (95% CI: 0.94, 0.97) and overall period survival was 0.34 (95% CI: 0.23, 0.46). Forest edge density had the strongest effect on nest survival. Nest survival decreased as forest edge density increased. Period survival tended to decrease as the breeding season progressed, but the 95% confidence intervals of the model-averaged parameter estimates overlapped. These results demonstrate that effective conservation strategies designed to provide high-quality breeding habitat for this endangered species should include measures to reduce predation by edge-adapted predators.
Environmental Correlates of Nesting Success in Red-Shouldered Hawks
Authors: Morrison Joan L. , McMILLIAN Michael , Cohen Jonathan B. , Catlin Daniel H.
Published: September 2019

Abstract. We evaluated the influence of weather on reproduction of the Red-shouldered Hawk (Buteo lineatus) in an agricultural landscape in south-central Florida where we found relatively high densities of successfully nesting hawks. We used a generalized linear modeling approach within an information-theoretic framework to examine the influence of total rainfall, rainfall frequency, and temperature on the timing of nesting, nesting success, and productivity of hawks during 1995–2000. The best models indicated an influence of rainfall frequency and laying period on hawk reproduction. During years with less frequent rainfall in the summer and fall months prior to the beginning of the breeding season, fewer pairs attempted to nest, and hawks nested later and had smaller clutch sizes and lower productivity. Hawks that nested later in the breeding season had lower hatching success and lower overall nest success. Although Red-shouldered Hawks are generally reported to inhabit forested landscapes throughout their range, a common feature seems to be a dependence on wetlands and riparian habitat for foraging. We propose that the proportion of wetlands throughout the landscape is a unique aspect of south-central Florida that may allow for persistence of unusually high numbers of hawks.
Corticosterone Levels in Relation to Change of Mate in Black-Legged Kittiwakes
Authors: Angelier Frederic , Moe BØRGE , Clement-Chastel Celine , Bech Claus , Chastel Olivier
Published: September 2019

Abstract. In birds, changing mates generally results in decreased breeding success. Although costs and benefits of pair break-up have been well studied, endocrine mechanisms associated with mate change are poorly known. We measured baseline and stress-induced corticosterone levels in relation to mate change in Black-legged Kittiwakes (Rissa tridactyla). Baseline corticosterone levels were higher in kittiwakes breeding with a new mate than in kittiwakes that did not change mate. Stress-induced corticosterone levels were not influenced by change of mate. Elevated baseline corticosterone levels in birds breeding with a new mate could result from the social stress associated with pair break-up or mirror a higher energetic demand resulting from a lack of coordination between new pair members. Our results emphasize the usefulness of corticosterone levels in elucidating the effects of mate change on the energetic demands of reproduction in free-living birds.
Are Nestlings the Cue for Reduction of the Adrenocortical Response to Stress in Male Yellow Warblers Breeding at High Latitude?
Authors: Morgan Wilson C. , Holberton Rebecca L.
Published: September 2019

Abstract. Acute corticosterone secretion helps individuals survive perturbation, particularly when faced with unpredictable conditions. However, elevated corticosterone is often incompatible with reproduction. Male Yellow Warblers (Dendroica petechia) breeding at high latitude avoid this conflict by exhibiting a reduced adrenocortical response while provisioning nestlings. To determine if this reduction is cued by nestlings, in June 2000 we switched clutches between nest pairs to manipulate hatching date. We sampled males with early-hatching clutches for the adrenocortical response 24 hr after nestlings hatched, but 24 hr prior to the premanipulated (original) hatching date. Similarly, we sampled males with late-hatching clutches 24 hr after the original hatching date, but prior to nestlings hatching. Males with early-hatching clutches (n  =  6) showed no reduced adrenocortical response, while males with late-hatching clutches (n  =  6) appeared to show a reduced response even without nestlings, suggesting that nestlings do not cue the reduction. An endogenous clock, day-counting mechanism, or hormonal changes may be associated with the reduced adrenocortical response.
Reproductive Biology of the Violet-Chested Hummingbird in Venezuela and Comparisons with Other Tropical and Temperate Hummingbirds
Authors: Fierro-Calderón Karolina , Martin Thomas E.
Published: September 2019

Abstract. We provide details on the breeding biology of the Violet-chested Hummingbird (Sternoclyta cyanopectus) based on 67 nests studied in Yacambú National Park, Venezuela, from 2002 through 2006. Clutch size was two white eggs, usually laid every other day. Fresh egg mass (0.95 ± 0.14 g) was 15% of female mass. Incubation and nestling periods were 20.4 ± 0.3 and 26.0 ± 0.4 days, respectively. Nest attentiveness increased from 60% in early incubation to 68% in late incubation. The female spent 50% of her time brooding young nestlings, but ceased brooding by 13 days of age. Only the female fed the young, with a low rate of nest visitation (3.3 trips per hour) that did not increase with age of the young. Growth rate based on nestling mass (K  =  0.28) was slow. Daily predation rates decreased across stages and were 0.064 ± 0.044, 0.033 ± 0.008, and 0.020 ± 0.006 during the egg-laying, incubation, and nestling periods, respectively. Most, but not all, life history traits of the Violet-chested Hummingbird were similar to those reported for other tropical and temperate hummingbirds, providing further evidence that this family shows a relatively narrow range of life history variation.
Using Color to Define Species Boundaries: Quantitative Analysis in the Orchard Oriole Complex Supports the Recognition of two Species
Authors: Kiere Lynna M. , Hofmann Christopher M. , Tracy Ian E. , Cronin Thomas W. , Leips Jeff , Omland Kevin E.
Published: September 2019

Abstract. The recent divergence of Orchard (Icterus spurius spurius) and Fuertes's Orioles (I. s. fuertesi) makes them an ideal system for investigating species boundaries. Orchard and Fuertes's Orioles differ in several respects. They have distinct breeding ranges—Fuertes's Orioles breed in eastern coastal Mexico, whereas Orchard Orioles breed throughout eastern and central North America—and differ in plumage coloration, with adult male Orchard Orioles appearing “chestnut” and Fuertes's Orioles “ochre.” However, no detailed quantitative color analyses have been conducted. To characterize these differences we quantitatively measured plumage color using reflectance spectrometry. The colored plumages of adult male Orchard and Fuertes's Orioles have unique spectral characteristics, with no color overlap between them. Combined with life history differences and previous molecular studies, these findings support the classification of Orchard and Fuertes's Orioles as separate species. Additionally, this study demonstrates the utility of quantitative color measurement as a tool for examining species boundaries.
On the Allometric Relationship Between Size and Composition of Avian Eggs: A Reassessment
Authors: Arnold Todd W. , Green Andy J.
Published: September 2019

Abstract. Numerous investigators have used allometric regression to characterize the relationship between proportional egg composition and egg size, which is a potentially important characterization for assessing maternal investment in reproduction. Herein, we document two important shortcomings of this approach. First, regressing log component mass against log egg mass involves regressing Y on itself, since each component (Y) is necessarily a part of the whole egg (X). This creates correlated errors, which leads to biased estimates of the regression slope. To circumvent this problem, we recommend regressing egg component masses on a relatively inert component like total water mass. Secondly, investigators routinely use ordinary least squares regression to estimate the slope of allometric relationships, which assumes that all error resides in Y. We demonstrate that this assumption is false, but so are the underlying error assumptions of commonly used alternatives such as reduced major axis and major axis regression. Because each egg is unique and determining composition involves destructive sampling, there is no obvious way to assess measurement error in Y versus X. As a solution, we recommend that investigators analyze multiple eggs per clutch whenever possible and fit a reduced major axis based on the among-female component of variability.
Home Range Attributes and Habitat Selection of Barred Owls and Spotted Owls in an Area of Sympatry
Authors: Hamer Thomas E. , Forsman Eric D. , Glenn Elizabeth M.
Published: September 2019

We compared home range areas and habitat selection of radio-marked Spotted Owls (Strix occidentalis) and Barred Owls (Strix varia) in an area of sympatry in the northern Cascade Range of Washington in 1986–1989. On average, home ranges of Spotted Owls were 3–4 times larger than ranges of Barred Owls, and there was little overlap of home ranges during the breeding season. Ranges of both species tended to expand during winter. Home range size of both species was negatively correlated with the amount of old forest, but the negative slope of the regression was much steeper for Spotted Owls than for Barred Owls. For both species, home ranges of individual owls typically had high overlap among seasons and years, indicating high site fidelity. Barred Owls generally occupied home ranges at lower elevations than Spotted Owls (mean  =  386 ± 27 m vs. 750 ± 68 m). Both species tended to use old forests more than expected, but Spotted Owls tended to use other cover types less than expected, whereas Barred Owls used most other cover types in proportion to their availability. We suggest that Spotted Owls may use larger ranges than Barred Owls because they prey selectively on a few species of nocturnal mammals, whereas Barred Owls forage more evenly across a broad range of prey types, including diurnal and aquatic species. The low overlap of Barred Owl and Spotted Owl home ranges suggests that territorial Barred Owls exclude Spotted Owls from their territories, at least during the breeding season, thus reducing the amount of habitat available to Spotted Owls.
Optimizing Nest Survival and Female Survival: Consequences of Nest Site Selection for Canada Geese
Authors: Miller David A. , Grand James B. , Fondell Thomas F. , Anthony R. MICHAEL
Published: September 2019

We examined the relationship between attributes of nest sites used by Canada Geese (Branta canadensis) in the Copper River Delta, Alaska, and patterns in nest and female survival. We aimed to determine whether nest site attributes related to nest and female survival differed and whether nest site attributes related to nest survival changed within and among years. Nest site attributes that we examined included vegetation at and surrounding the nest, as well as associations with other nesting birds. Optimal nest site characteristics were different depending on whether nest survival or female survival was examined. Prior to 25 May, the odds of daily survival for nests in tall shrubs and on islands were 2.92 and 2.26 times greater, respectively, than for nests in short shrub sites. Bald Eagles (Halieaeetus leucocephalus) are the major predator during the early breeding season and their behavior was likely important in determining this pattern. After 25 May, when eagle predation is limited due to the availability of alternative prey, no differences in nest survival among the nest site types were found. In addition, nest survival was positively related to the density of other Canada Goose nests near the nest site. Although the number of detected mortalities for females was relatively low, a clear pattern was found, with mortality three times more likely at nest sites dominated by high shrub density within 50 m than at open sites dominated by low shrub density. The negative relationship of nest concealment and adult survival is consistent with that found in other studies of ground-nesting birds. Physical barriers that limited access to nest sites by predators and sites that allowed for early detection of predators were important characteristics of nest site quality for Canada Geese and nest site quality shifted within seasons, likely as a result of shifting predator-prey interactions.
Survival of Postfledging Grassland Birds in Missouri
Authors: Suedkamp Wells Kimberly M. , Ryan Mark R. , Millspaugh Joshua J. , Thompson Frank R. , Hubbard Michael W.
Published: September 2019

We describe survival patterns during the postfledging period for two species of grassland birds in Missouri. We monitored 155 radio-marked juvenile Dickcissels (Spiza americana) and 107 juvenile Eastern Meadowlarks (Sturnella magna; hereafter meadowlark) in southwestern Missouri, from 2002 to 2004. We used an information theoretic approach to evaluate support for biological, temporal, and spatial covariates on survival estimates using Cox proportional hazards models, and also identified cause-specific mortality. For Dickcissels, the model with biological covariates containing body mass had the lowest score using Akaike's information criterion, corrected for small sample sizes (AICc) and almost twice the support of the second-best model. For meadowlarks, the null model had the lowest AICc score, but the second-best model containing body mass was also competitive (within 2 AICc units), so we used the latter model for inference. Hazard ratios indicated that a 1 g increase in body mass was associated with a 3% (Dickcissels) and 2% (meadowlarks) reduction in the risk of death. The cumulative probability of surviving the study period (Dickcissels, 58 days, meadowlarks, 72 days) was 0.56 (95% CI: 0.49–0.65) for Dickcissels and 0.63 (95% CI: 0.54–0.74) for meadowlarks. Predation was the largest source of cause-specific mortality for both species and responsible for 56% (Dickcissels) and 70% (meadowlarks) of deaths. Snakes were the numerically dominant predator of juvenile Dickcissels, but there was not a numerically dominant predator of juvenile meadowlarks. Our results emphasize the importance of body condition on postfledging survival. Future studies should consider estimating postfledging survival rates within species across systems to understand the potential impacts of different predator communities on juvenile survival.
Stopover Ecology and Habitat Selection of Juvenile Swainson's Thrushes During Fall Migration Along the Northern California Coast
Authors: Tietz James R. , Johnson Matthew D.
Published: September 2019

We investigated selection of stopover habitat by juvenile Swainson's Thrushes (Catharus ustulatus) during fall migration at a site along the northern California coast. The study site vegetation consisted mainly of coniferous forest (pine [Pinus] and spruce [Picea]), with interspersed patches of broadleaf forest (willow [Salix] and alder [Alnus]) in poorly drained swales. For 26 birds captured and radio-tracked in 2002 and 2003, the average minimum stopover duration was 8.9 ± 1.0 days. For 20 of these birds with a sufficient number of locations, the average home range size was 1.9 ± 0.3 ha. Thrushes showed no overall pattern of selection for forest type within the study area or for forest type used inside their home range. Fat and lean birds selected forest types similarly within the study area and their home ranges. However, locations occupied by lean birds had twice as much huckleberry (Vaccinium ovatum) shrub cover and were 1.3 times more concealed by vegetation than locations occupied by fat birds. There were 2.5 times more huckleberries at occupied than random locations, and locations occupied by lean birds had 2.1 times more berries overall than those frequented by fat birds. Fecal analyses confirmed that huckleberries were a commonly consumed food (70% of sampled thrushes), but also revealed that thrushes ate arthropods (87%) and wax myrtle (Myrica californica) bracteoles (43%). The overall lack of forest type selection coupled with differences between fat and lean birds in selection for cover and fruit abundance suggests that fat level may influence microsite selection.
Diet, Food Preferences, and Digestive Efficiency of the Grayish Saltator, a Partly Folivorous Passerine
Authors: Rodríguez-Ferraro Adriana , García-Amado M. Alexandra , Bosque Carlos
Published: September 2019

We studied the diet of the Grayish Saltator (Saltator coerulescens) during the rainy and dry seasons in the Venezuelan llanos and examined its food preferences, digesta retention time, rate of food intake, and digestive efficiency, in captivity. Grayish Saltators fed almost exclusively on plant tissues throughout the year. Fruits and leaves were the most commonly consumed items, comprising 36% and 28% of the diet, respectively, averaged over the entire year. In pairwise choice trials, saltators preferred fruits over leaves and flowers, and wild over cultivated leaves. In the laboratory, saltators displayed food-processing traits typical of frugivorous passerines. When feeding on a fruit (banana mash) diet, they had a fast rate of food passage (digesta mean retention time  =  54 ± 26 min) and a relatively low digestive efficiency (average metabolizable energy coefficient  =  0.59 ± 0.11), which was compensated for by high rates of food intake (1.4 times body mass). Mean retention time of a leaf-supplemented diet was slightly shorter (average  =  45 ± 17 min). Birds maintained or increased their body masses under laboratory conditions when fed on a fruit diet but did not when fed exclusively with leaves. Saltators spent very little time foraging, and the amount of time varied seasonally (5% and 17% of the time in the rainy and dry seasons, respectively). Most of their time (ca. 50%) was dedicated to resting. The morphology of the digestive tract of this species is similar to other frugivorous birds, but the inner edge of the maxilla is serrated. We found no evidence of cellulolytic activity in the Grayish Saltator's gut. Together, all of these characteristics indicate that Grayish Saltators are partial folivores that rely on a “skimming” strategy of food consumption.
Diet of the Cauca Guan: Exploitation of a Novel Food Source in Times of Scarcity
Authors: Muñoz Marcia C. , Londoño Gustavo A. , Rios Margarita M. , Kattan Gustavo H.
Published: September 2019

Although exotic species may have a negative impact on native organisms, they can in some cases provide abundant resources. Use of these resources may have important implications for habitat use, movement, and space requirements of native animals, and ultimately for population dynamics. We describe the diet of a population of the narrowly endemic Cauca Guan (Penelope perspicax) in the Colombian Andes. This guan demonstrates plasticity in its eating habits, feeding on an exotic tree species during periods of food scarcity. Based on direct observations and analysis of fecal samples over a one-year cycle, we found that guans fed on 89 species of fruits but also included foliage, flowers, and invertebrates in their diets. Guans fed on fruit species in proportion to their availability but favored some species with high fruit production or prolonged fruiting. Fruit availability, measured both in numbers of species and biomass, varied throughout the year, with a low in September–December. During the period of low fruit availability, guans congregated in large numbers at a Chinese ash (Fraxinus chinensis) plantation, where they fed on young leaves in large quantities. Ash was planted at this site over 40 years ago as part of a reforestation program, and plantations are invaded by native vegetation. Guans are abundant at this site, and seasonal consumption of ash foliage, a concentrated and abundant food source, may have influenced local population dynamics.
Contaminants in Lesser Scaup Eggs and Blood from Yukon Flats National Wildlife Refuge, Alaska
Authors: Matz Angela C. , Rocque Deborah A.
Published: September 2019

Documented declines in Lesser Scaup (Aythya affinis) populations may be caused by several factors, including reduced reproductive success or survival from exposure to environmental contaminants during winter, migration, or breeding. We evaluated organochlorines and inorganic elements in Lesser Scaup blood (n  =  14) and eggs (n  =  10) from a breeding area in the relatively pristine Yukon Flats National Wildlife Refuge in interior Alaska. Most contaminants were not at concentrations of concern. Lead was detected in only four blood samples, with an average when detected (0.29 mg kg−1 wet weight [ww]) slightly above background levels (0.20 mg kg−1 ww). Our study area had little or no hunting, but since lead exposure is correlated with hunting pressure, lead should be evaluated in other Lesser Scaup breeding areas. Strontium in eggs (mean  =  10.90 mg kg−1 dry weight [dw]) was significantly negatively correlated with eggshell thickness. Eggshell thickness was also 18% lower than in museum specimens, a percentage associated with population declines in other species, and was not correlated with other contaminants. Few comparative data in the literature exist, but productivity in this breeding area was low (mean nest success  =  12%), so further research on the effects of strontium on productivity through the mechanism of eggshell thinning is needed. Most environmental contaminants are unlikely to be affecting Lesser Scaup populations breeding in interior Alaska, but lead and strontium should be studied further.
Selenium Accumulation in European Starlings Nesting in a Selenium-Contaminated Environment
Authors: Santolo Gary M.
Published: September 2019

I compared selenium (Se) levels in blood, liver, egg, and diet samples from European Starlings (Sturnus vulgaris) nesting at Kesterson Reservoir, Merced County, California and the surrounding area. Concentrations were highest in adult and nestling blood (8.3 and 5.5 µg g−1, respectively), nestling liver (7.5 µg g−1), and eggs (4.6 µg g−1) from nest boxes in interior parts of Kesterson compared to those from the perimeter (adult and nestling blood  =  4.0 and 1.4 µg g−1, respectively, nestling liver  =  4.7 µg g−1, eggs  =  2.8 µg g−1) and off-site (nestling blood  =  3.8 µg g−1, liver  =  4.3 µg g−1, egg  =  2.7 µg g−1). No hatching failure or embryo effects were observed. Although I found strong positive relationships in Se levels among tissues and eggs, variability of dietary exposure and differences in depuration rates across tissues confounds prediction of Se concentration. Nevertheless, I found blood Se to be a good indicator of dietary exposure that can be sampled nondestructively.
Does Sea Ice Constrain the Breeding Schedules of High Arctic Northern Fulmars?
Authors: Mallory Mark L. , Forbes Mark R.
Published: September 2019

The Northern Fulmar (Fulmarus glacialis) is a pelagic seabird that breeds across 25° of latitude, from the boreal to the high Arctic oceanographic zones. We examined the breeding schedule of fulmars in the remote Cape Vera colony in the Canadian high Arctic, a marine region covered by sea ice much of the year, to determine if the timing of breeding and colony attendance patterns of birds differed from the breeding phenology of fulmars in colonies farther south. Cape Vera fulmars arrived at the colony later in the year, spent less time at the colony before egg-laying, and took a significantly longer prelaying exodus from the colony compared to fulmars nesting in more southerly colonies. After egg-laying, however, patterns of colony attendance by fulmars in the high Arctic were similar to patterns for fulmars in southern colonies; this part of the fulmar breeding schedule may be inflexible. The differences in breeding schedules across the species' range might reflect behavioral adaptations by arctic-nesting birds to accommodate the physical and biological limitations imposed by extensive sea ice near arctic colonies, particularly early in the breeding season. Given that climate warming and corresponding reductions in sea ice are taking place in the Arctic, it remains to be determined whether fulmars in the high Arctic have the behavioral flexibility in their breeding phenology to compensate for rapidly occurring changes in their environment.
A Small Representative of the Phalacrocoracoidea (Cormorants and Anhingas) from the Late Oligocene of Germany
Authors: Mayr Gerald
Published: September 2019

I describe a skeleton of a cormorant-like bird from Enspel, a late Oligocene (24.7 mya) fossil site in Germany, which is assigned to a new species, ?Borvocarbo stoeffelensis, sp. nov. The specimen constitutes the earliest described and most completely preserved fossil record of the Phalacrocoracoidea, the clade including Anhingidae (anhingas) and Phalacrocoracidae (cormorants). ?B. stoeffelensis shares derived features with cormorants that are absent in anhingas. Despite its cormorant-like overall morphology, an assignment to the stem lineage of Phalacrocoracidae is not straightforward, because the new species is also distinguished from crown group representatives of the clade (Anhingidae + Phalacrocoracidae) by presumably plesiomorphic features. The morphology displayed by ?B. stoeffelensis places a caveat on the assignment to the Phalacrocoracidae of other less completely known Paleogene and early Neogene taxa. Plesiomorphic features shared by ?B. stoeffelensis and extant “microcormorants” (sensu Siegel-Causey 1988) support a sister group relationship between “Microcarbo” spp. and all other extant Phalacrocoracidae.
Genetic Variability and Taxonomic Status of the Nihoa and Laysan Millerbirds
Authors: Fleischer Robert C. , Slikas Beth , Beadell Jon , Atkins Colm , McINTOSH Carl E. , Conant Sheila
Published: September 2019

The Millerbird (Acrocephalus familiaris) is an endemic Northwestern Hawaiian Islands reed warbler that existed until about 1923 on Laysan Island (A. f. familiaris) and currently occurs in a small population on Nihoa Island (A. f. kingi). The two populations are described as separate subspecies or species on the basis of size and plumage differences. We assessed genetic variation in blood samples from 15 individuals in the modern Nihoa population using approximately 3000 base pairs (bp) of mitochondrial DNA (mtDNA) sequence and 14 microsatellite loci. We also obtained up to 1028 bp of mtDNA sequence from the fragmented DNA of museum specimens of three birds collected on Nihoa in 1923 and five birds collected on Laysan in 1902 and 1911 (ancient samples). Genetic variation in both marker types was extremely low in the modern Nihoa population (nucleotide diversity [π]  =  0.00005 for mtDNA sequences; observed heterozygosity was 7.2% for the microsatellite loci). In contrast, we found three mtDNA haplotypes among the five Laysan individuals (π  =  0.0023), indicating substantially greater genetic variation. The Nihoa and Laysan taxa differed by 1.7% uncorrected mtDNA sequence divergence, a magnitude that would support designation at the subspecies, and perhaps species, level relative to other closely related Acrocephalus species pairs. However, in light of strong ecological similarity between the two taxa, and a need to have additional populations to prevent extinction from stochastic effects and catastrophes, we believe these genetic differences should not deter a potential translocation of individuals from Nihoa to Laysan.
Song Learning After Isolation in the Open-Ended Learner the European Starling: Dissociation of Imitation and Syntactic Development
Authors: Chaiken Martha Leah , BÖHNER JÖRG
Published: September 2019

We performed two studies to test whether the ability of open-ended learners to acquire new songs as adults depends on their having learned normal songs as juveniles. European Starlings (Sturnus vulgaris) were kept in isolation for their first year. In the first study the birds were housed in a group with a wild-caught adult male following isolation. The subjects imitated each other but not the wild male and failed to develop normal phonology or syntax. In the second study each yearling was housed individually with a wild-caught adult male following isolation. These subjects developed good phonology and syntax but copied few or no song motifs from the wild adults. Taken together, the two studies indicate that starlings are capable of imitating new motifs and of acquiring species-typical phonology and syntax after a year of isolation. The contrasting results of the two studies suggest that imitation and the development of syntax are independent processes subject to different influences.
A trajectory mechanics approach for the study of wave propagation in an anisotropic elastic medium
Authors: Vasco D W , Nihei Kurt T
Published: September 2019

We derive equations describing the path and traveltime of a coherent elastic wave propagating in an anisotropic medium, generalizing expressions from conventional high-frequency asymptotic ray theory. The methodology is valid across a broad range of frequencies and allows for subwavelength variations in the material properties of the medium. The primary difference from current ray methods is the retention of a term that is neglected in the derivation of the eikonal equation. The additional term contains spatial derivatives of the properties of the medium and of the amplitude field, and its presence couples the equations governing the evolution of the amplitude and phase along the trajectory. The magnitude of this term provides a measure of the validity of expressions based upon high-frequency asymptotic methods, such as the eikonal equation, when modelling wave propagation dominated by a band of frequencies. In calculations involving a layer with gradational boundaries, we find that asymptotic estimates do deviate from those of our frequency-dependent approach when the width of the layer boundaries become sufficiently narrow. For example, for a layer with boundaries that vary over tens of meters, the term neglected by a high-frequency asymptotic approximation is significant for frequencies around 10 Hz. The visible differences in the paths of the rays that traverse the layer substantiate this conclusion. For a velocity model derived from an observed well log, the majority of the trajectories calculated using the extended approach, accounting for the frequency-dependence of the rays, are noticeably different from those produced by the eikonal equation. A suite of paths from a source to a specified receiver, calculated for a range of frequencies between 10 and 100 Hz, define a region of sensitivity to velocity variations and may be used for an augmented form of tomographic imaging.
Diabetes epidemics: inequalities increase the burden on the healthcare system
Authors: Santamaría-Ulloa Carolina , Montero-López Melina , Rosero-Bixby Luis
Published: September 2019

Diabetes is a major cause of morbidity and mortality and represents a source of demands on already constrained healthcare systems in Latin America and the Caribbean. We estimate inequalities in diabetes incidence, prevalence and mortality and assess the economic burden on the healthcare system in Costa Rica. The main source of data is the Costa Rican Longevity and Healthy Aging Study, a longitudinal nationally representative survey of the elderly population (n = 2827). Data analyses include descriptive statistics, multiple regression models and survival analysis models. More than a fifth of Costa Rican elderly experience diabetes. Incidence is estimated at 5 per 1000 person-years in the population 30+. Gender and geographical inequalities were found. Men have a significantly lower prevalence (16.51% vs 24.02%, P < 0.05) and incidence (4.3 vs 6.0 per 1000 person-years, P < 0.05), but higher mortality (hazard ratio = 1.31, P < 0.01). Longer time to the closest facility translates into a lower probability of having the condition diagnosed [odds ratio (OR) = 0.77, P < 0.05]. The diabetic as compared to the non-diabetic population imposes a larger economic burden on the healthcare system with a higher probability of using outpatient care (OR = 3.08, P < 0.01), medications (OR = 3.44, P < 0.01) and hospitalizations (OR = 1.24, P > 0.05). Individuals living in the Metro Area have a significantly lower probability of being hospitalized (OR = 0.72, P < 0.05), which may be evidence of better access to primary care that prevents hospitalization. Along the same line, women have higher utilization rates of outpatient care (OR = 2.02, P < 0.01) and medications (OR = 1.73, P < 0.01), which may contribute to lower odds of hospitalization (OR = 0.61, P < 0.01). Aligned with the aim of attaining Sustainable Development Goals, this study highlights the importance of generating health policies focused on prevention of diabetes that take into consideration gender and geographical inequalities. Strategies should booster preventive healthcare utilization by men and aim to make healthcare services accessible to all, regardless of geographical location.
Transcendental Liouville Inequalities on Projective Varieties
Authors: Gasbarri Carlo
Published: September 2019

Let $p$ be an algebraic point of a projective variety $X$ defined over a number field. Liouville inequality tells us that the norm at $p$ of a non-vanishing integral global section of a hermitian line bundle over $X$ is zero or it cannot be too small with respect to the $\sup $ norm of the section itself. We study inequalities similar to Liouville’s for subvarietes and for transcendental points of a projective variety defined over a number field. We prove that almost all transcendental points verify a good inequality of Liouville type. We also relate our methods to a (former) conjecture by Chudnovsky and give two applications to the growth of the number of rational points of bounded height on the image of an analytic map from a disk to a projective variety.
The Impact of Actotoxumab Treatment of Gnotobiotic Piglets Infected With Different Clostridium difficile Isogenic Mutants
Authors: Danz Hillary R , Lee Sangun , Chapman-Bonofiglio Susan P , Ginese Melanie , Beamer Gillian , Girouard Donald J , Tzipori Saul
Published: September 2019

Nosocomial infections with Clostridium difficile are on the rise in the Unites States, attributed to emergence of antibiotic-resistant and hypervirulent strains associated with greater likelihood of recurrent infections. In addition to antibiotics, treatment with Merck anti-toxin B (TcdB) antibody bezlotoxumab is reported to reduce recurrent infections. However, treatment with anti-toxin A (TcdA) antibody actotoxumab was associated with dramatically increased disease severity and mortality rates in humans and gnotobiotic piglets. Using isogenic mutants of C. difficile strain NAPI/BI/027 deficient in TcdA (A−B+) or TcdB (A+B−), and the wild type, we investigated how and why treatment of infected animals with anti-TcdA dramatically increased disease severity. Contrary to the hypothesis, among piglets treated with anti-TcdA, those with A+B− infection were disease free, in contrast to the disease enhancement seen in those with wild-type or A−B+ infection. It seems that the lack of TcdA, through either deletion or neutralization with anti-TcdA, reduces a competitive pressure, allowing TcdB to freely exert its profound effect, leading to increased mucosal injury and disease severity.