bluuebunny/crossref_metadata_2025 huggingface dataset:
An implicit lipid model for efficient reaction-diffusion simulations of protein binding to surfaces of arbitrary topology
Authors: Fu Yiben , Yogurtcu Osman N. , Kothari Ruchita , Thorkelsdottir Gudrun , Sodt Alexander J. , Johnson Margaret E.
Published: September 2019

Localization of proteins to a membrane is an essential step in a broad range of biological processes such as signaling, virion formation, and clathrin-mediated endocytosis. The strength and specificity of proteins binding to a membrane depend on the lipid composition. Single-particle reaction-diffusion methods offer a powerful tool for capturing lipid-specific binding to membrane surfaces by treating lipids explicitly as individual diffusible binding sites. However, modeling lipid particle populations is expensive. Here, we present an algorithm for reversible binding of proteins to continuum surfaces with implicit lipids, providing dramatic speed-ups to many body simulations. Our algorithm can be readily integrated into most reaction-diffusion software packages. We characterize changes to kinetics that emerge from explicit vs implicit lipids as well as surface adsorption models, showing excellent agreement between our method and the full explicit lipid model. Compared to models of surface adsorption, which couple together binding affinity and lipid concentration, our implicit lipid model decouples them to provide more flexibility for controlling surface binding properties and lipid inhomogeneity, thus reproducing binding kinetics and equilibria. Crucially, we demonstrate our method’s application to membranes of arbitrary curvature and topology, modeled via a subdivision limit surface, again showing excellent agreement with explicit lipid simulations. Unlike adsorption models, our method retains the ability to bind lipids after proteins are localized to the surface (through, e.g., a protein-protein interaction), which can greatly increase the stability of multiprotein complexes on the surface. Our method will enable efficient cell-scale simulations involving proteins localizing to realistic membrane models, which is a critical step for predictive modeling and quantification of in vitro and in vivo dynamics.
Simulation of semidilute polymer solutions in planar extensional flow via conformationally averaged Brownian noise
Authors: Young Charles D. , Sing Charles E.
Published: September 2019

The dynamics and rheology of semidilute polymer solutions in strong flows are of great practical relevance. Processing applications can in principle be designed utilizing the relationship between nonequilibrium polymer conformations and the material properties of the solution. However, the interplay between concentration, flow, hydrodynamic interactions (HIs), and topological interactions which govern semidilute polymer dynamics is challenging to characterize. Brownian dynamics (BD) simulations are particularly valuable as a way to directly visualize how molecular interactions arise in these systems and are quantitatively comparable to single-molecule experiments. However, such simulations are often computationally intractable and are limited by the need to calculate the correlated Brownian noise via decomposition of the diffusion tensor. Previously, we have introduced an iterative conformational averaging (CA) method for BD simulations which bypasses these limitations by preaveraging the HI and Brownian noise in an iterative procedure. In this work, we generalize the CA method to flowing semidilute solutions by introducing a conformation dependent diffusion tensor and a strain dependent approximation to the conformationally averaged Brownian noise. We find that this approach nearly quantitatively reproduces both transient and steady state polymer dynamics and rheology while achieving an order of magnitude computational acceleration. We then utilize the CA method to investigate the concentration and flow rate dependence of polymer dynamics in planar extensional flows. Our results are consistent with previous experimental and simulation studies and provide a detailed view of broad conformational distributions in the semidilute regime. We observe interconversion between stretched and coiled states at steady state, which we conjecture occur due to the effect of concentration on the conformation dependent polymer drag. Additionally, we observe transient flow-induced intermolecular hooks in the startup of flow which lead to diverse and unique stretching pathways.
A ZIF-67-derived–sulfur sandwich structure for high performance Li–S batteries
Authors: Gao Xing , Li Siwu , Du Ying , Wang Bo
Published: September 2019

Herein, a novel ZIF-67-derived material, PZ67, is developed as an effective coating to construct a sandwich-structured electrode for high performance lithium sulfur batteries. Taking advantage of the synergistic effect of chemical interaction, physical barrier, and high conductivity of PZ67 coatings, we found that the PZ67/S/PZ67 structured cathode can effectively enhance the active materials reaction kinetics, prohibit the shuttling effect, and improve the batteries’ cycling performance, achieving a superior electrochemical performance. It delivers an initial capacity of 1158.1 mA h g−1 and retains at 715 mA h g−1 after 300 cycles, which is more than twice of that of a bare sulfur-based cell. Even at the current density of 1 C, the discharge capacity still approaches 916.7 mA h g−1.
Middle to Late Paleocene Leguminosae fruits and leaves from Colombia
Authors: Herrera Fabiany , Carvalho Mónica R. , Wing Scott L. , Jaramillo Carlos , Herendeen Patrick S.
Published: September 2019

Leguminosae are one of the most diverse flowering-plant groups today, but the evolutionary history of the family remains obscure because of the scarce early fossil record, particularly from lowland tropics. Here, we report ~500 compression or impression specimens with distinctive legume features collected from the Cerrejón and Bogotá Formations, Middle to Late Paleocene of Colombia. The specimens were segregated into eight fruit and six leaf morphotypes. Two bipinnate leaf morphotypes are confidently placed in the Caesalpinioideae and are the earliest record of this subfamily. Two of the fruit morphotypes are placed in the Detarioideae and Dialioideae. All other fruit and leaf morphotypes show similarities with more than one subfamily or their affinities remain uncertain. The abundant fossil fruits and leaves described here show that Leguminosae was the most important component of the earliest rainforests in northern South America c. 60–58 million years ago.
Mating yeast cells use an intrinsic polarity site to assemble a pheromone-gradient tracking machine
Authors: Wang Xin , Tian Wei , Banh Bryan T. , Statler Bethanie-Michelle , Liang Jie , Stone David E.
Published: September 2019

The mating of budding yeast depends on chemotropism, a fundamental cellular process. The two yeast mating types secrete peptide pheromones that bind to GPCRs on cells of the opposite type. Cells find and contact a partner by determining the direction of the pheromone source and polarizing their growth toward it. Actin-directed secretion to the chemotropic growth site (CS) generates a mating projection. When pheromone-stimulated cells are unable to sense a gradient, they form mating projections where they would have budded in the next cell cycle, at a position called the default polarity site (DS). Numerous models have been proposed to explain yeast gradient sensing, but none address how cells reliably switch from the intrinsically determined DS to the gradient-aligned CS, despite a weak spatial signal. Here we demonstrate that, in mating cells, the initially uniform receptor and G protein first polarize to the DS, then redistribute along the plasma membrane until they reach the CS. Our data indicate that signaling, polarity, and trafficking proteins localize to the DS during assembly of what we call the gradient tracking machine (GTM). Differential activation of the receptor triggers feedback mechanisms that bias exocytosis upgradient and endocytosis downgradient, thus enabling redistribution of the GTM toward the pheromone source. The GTM stabilizes when the receptor peak centers at the CS and the endocytic machinery surrounds it. A computational model simulates GTM tracking and stabilization and correctly predicts that its assembly at a single site contributes to mating fidelity.
Inequalities in exposure to the air pollutants PM2.5 and NO2 in Australia
Authors: Cooper Nathan , Green Donna , Knibbs Luke D
Published: September 2019

Vulnerable subpopulations may be exposed to higher levels of outdoor air pollution than the rest of the population. Due to the potential for this to exacerbate their existing health burden, concerns about disparities in subpopulations’ air pollution exposure have motivated international public health researchers to examine this topic. In Australia, such research is lacking to date, despite heterogeneity in air pollution at multiple spatial scales across the continent. This study aimed to investigate disparities in exposure to two health-relevant outdoor air pollutants: particulate matter <2.5 μm (PM2.5) and nitrogen dioxide (NO2). We used national land-use regression models to estimate annual average concentrations of PM2.5 and NO2, and area-level census data on ethnicity, age and socio-economic status (SES) to calculate the bivariate associations between each census-derived variable with the concentration of air pollutants. We also used multivariable models including specific measures of SES as covariates to assess to what extent associations were explained by SES. Associations were calculated separately for rural and urban areas using generalised additive models which accounted for spatial autocorrelation. Bivariate results showed significant nonlinear associations (p < 0.001) between vulnerable subpopulations and pollutant concentration. These associations suggested that areas with greater socio-economic disadvantage, a higher proportion of ethnic minorities, and elderly people are exposed to higher concentrations of PM2.5 and NO2, although differences in the magnitude of exposure were small overall. Our multivariable models showed that the associations between ethnic minorities and pollutant concentration appear to be substantially affected by area-level SES. Our results suggested that these vulnerable subpopulations are inequitably exposed to PM2.5 and NO2. While the magnitude of differences in exposure were generally small, the predicted differences in exposure among vulnerable subpopulations could contribute to a potentially avertable health burden at a population-level.
The Common Agricultural Policy: A Case of Embedded Liberalism
Authors: Roederer-Rynning Christilla
Published: September 2019

The Common Agricultural Policy (CAP) can be fruitfully construed as an instance of European embedded liberalism, shaped by overlapping layers of domestic, European Union, and international policymaking. Such a conceptualization reveals the large role of domestic politics, even in an area like the CAP, where policy competences were early on extensively transferred to the supranational level. This in turn reflects the rather prominent role of national governments in the EU construction, compared with traditional federal polities. This role can be probed by analyzing two related scholarly agendas: an agenda devoted to the shaping of the CAP by member states (policy shaping); and an agenda devoted to the domestic impact of the CAP. Current policy challenges highlight our need to develop our understanding of: (1) the interaction between different types of CAP decisions at the EU level; (2) the domestic impact of the CAP; (3) and the experience of Central and Eastern European Countries (CEEC).
Monophyly of the Piciformes: A Reply to Olson
Authors: Raikow Robert J. , Cracraft Joel
Published: September 2019

Olson (1983) questioned the hypothesis that the order Piciformes is monophyletic and suggested instead that each piciform suborder is allied with a nonpiciform group. His attempt to discredit the synapomorphies joining the Galbulae and Pici is refuted by corrections of his interpretations of previous work. The Piciformes share a complex derived hindlimb morphology involving zygodactyly, a tripartite flexor hallucis longus, and Type VI flexor tendons. Olson's argument for polyphyly combines inadequate data with the inappropriate technique of equating general overall similarity with affinity. His hypothesis is therefore rejected. Problems concerning fossil taxa are also discussed. Based on current information, we believe that a monophyletic origin of the Piciformes remains the hypothesis of choice.
Harlan's Hawk (Buteo jamaicensis harlani): A Valid Subspecies
Authors: Mindell David P.
Published: September 2019

During surveys of 19 different rivers in central and southwestern Alaska, north of the Alaska Peninsula, all Red-tailed Hawks (Buteo jamaicensis) seen were either B. j. harlani or harlani intergrades, demonstrating that harlani does have a breeding range exclusive of other Red-tailed Hawk subspecies and is, therefore, a legitimate subspecies. The range of harlani intergrades was widespread and overlapped the harlani breeding range entirely. The findings presented suggest that the breeding range for harlani and its intergrade forms, exclusive of other Red-tailed Hawk subspecies, is: west to Norton Sound, east to the Alaska Range west slope, north to the tree line, and south to the Alaska Peninsula. Harlani may have diverged morphologically from other Red-tailed Hawks by isolation in a Pleistocene epoch glacial refugium, as has been suggested for other northern bird groups. The possibility of paripatric speciation, however, must also be considered. The characteristics of red in the tail (even small amounts) and white body plumage are discussed as likely intergrade traits.
Variability in Island Populations of the House Finch
Authors: Power Dennis M.
Published: September 2019

Coefficients of variation and generalized variances are compared for nine morphological characters from five mainland and four island populations of the House Finch (Carpodacus mexicanus). The purpose is to test the idea that variability is reduced in isolated populations and that there is a "population variation parameter" that determines the level of variation in most characters. Variability is greater in bill characters for Guadalupe and San Benito Islands than for mainland and other island populations. There are no consistent differences among samples in variability of wing, tail, or hind-limb characters, except for a tendency toward increased tarsus-length variability in a southern Baja California population and reduced variability in this character in San Clemente Island and Guadalupe Island populations. In bill characters, increased variability is found in the most divergent populations. The results do not support the generalization that geographic (= genetic) isolation per se causes much of a change in variability in island populations of birds, nor is there support for the idea of a pervasive quality of the gene pool that determines the level of variability in most characters.
Population Studies of the Polyandrous Spotted Sandpiper
Authors: Oring Lewis W. , Lank David B. , Maxson Stephen J.
Published: September 2019

A color-banded population of Spotted Sandpipers (Actitis macularia) was studied over a 10-yr period on Little Pelican Island, Leech Lake, Minnesota. A total of 75 females and 107 males bred for 144 ♀ ♀ yr and 200 ♂ ♂ yr. The observed skew in the population sex ratio was due primarily to behavioral exclusion of inexperienced females. Density appeared to limit population size and productivity. Locally hatched chicks accounted for 31% and 40% of the breeding females in the final 2 yr. Females laid eggs for 1.35-2.06 males per year. Experienced females had significantly more mates, eggs, chicks, and fledglings than did inexperienced females. Locally hatched chicks accounted for 21% and 19% of the breeding males in the final 2 yr. Males mated with 1.0-1.4 females per year. Experienced males had more mates and received more replacement eggs than did inexperienced males; in contrast to females, however, inexperienced males had no less hatching or fledging success than did experienced males. Thirty-eight marked females and 16 marked males tried unsuccessfully to enter the population, and 6 females and no males were observed to be nonbreeders all season long. Of 1,142 eggs, 442 hatched and 256 fledged. Experienced birds returned to breed more often in subsequent years than did inexperienced ones (61% vs. 50%). Return rates of successful birds were consistently higher than those of unsuccessful birds, the difference decreasing with age. Young males appeared to be less site-faithful than were females and older males. Successfully breeding females lived an average of 3.7 yr. Relative to other scolopacids with multipurpose territories, the Spotted Sandpiper is considered a pioneering species that quickly and frequently colonizes new sites, emigrates in response to reproductive failure, breeds first at an early age, lives a relatively short time, lays many eggs per female per year, and has relatively low nest success.
Pacific Coast Caspian Terns: Dynamics of an Expanding Population
Authors: Gill Robert E. , Mewaldt L. Richard
Published: September 2019

Nesting distribution, age-related seasonal movements, survivorship, and mechanisms of population expansion in Pacific Coast Caspian Terns (Sterna caspia) were examined primarily through analysis of 412 recoveries of birds banded as juveniles between 1935 and 1980. Since the beginning of this century, the population has shifted from nesting in numerous small colonies associated with freshwater marshes in interior California and southern Oregon to nesting primarily in large colonies on human-created habitats along the coast. Colonies at Grays Harbor, Washington and San Francisco and San Diego bays, California account for 77% of the current Pacific Coast population (6,000 pairs), which has breeding and wintering areas separate from those of populations east of the continental divide. There also appears to be some segregation on the wintering grounds by birds from the three major colonies within the Pacific population. Age-related seasonal movements in the Pacific population are characterized by (1) a brief period of northward dispersal by newly fledged birds before migrating to the wintering grounds, (2) a residency on the wintering grounds through their second winter, (3) a return to the breeding grounds the third summer, when most birds are thought to prospect breeding sites and some may breed, and (4) attainment of adulthood the fourth summer, with subsequent annual movements between wintering and breeding grounds.

The Pacific population has increased 70% since 1960, apparently all by intrinsic growth. Over half (57%) of the fledglings reach their fourth year, and they have a subsequent annual survival rate of 89% and a mean breeding life expectancy of 8.6 yr. An average annual fledging rate of 0.64 young per pair was calculated as necessary to have provided the observed growth of the population during its recent expansion. Growth of some of the individual colonies, however, particularly those in Washington, could only have resulted from extensive recruitment of birds from other Pacific Coast colonies. Philopatry is low in this population, and the growth of the northern colonies involved recruitment primarily of first-time breeders but also of some older adults. Factors promoting both first-time breeders and older adults to join new and often distant colonies are discussed.
“Replacements” of Landbird Species on Socorro Island, Mexico
Authors: Jehl Joseph R. , Parkes Kenneth C.
Published: September 2019

The endemic dove Zenaida graysoni of Socorro Island, an oceanic island in the Pacific south of Baja California, became extirpated between 1958 and 1978, and the endemic mockingbird Mimodes graysoni diminished during the same years and was approaching extinction by 1981. The mainland Mourning Dove Z. macroura became established on Socorro between (probably) 1971 and 1978, and the mainland Northern Mockingbird Mimus polyglottos between 1978 and 1981. Superficially an instance of replacement of island endemics by mainland relatives through competitive exclusion, the case is actually more complicated. We argue that extermination of the endemics was probably caused by predation by feral cats introduced in 1957 or later. There is no evidence of any actual competition between the pairs of species, and their preferred habitats overlap only slightly. We attribute the nearly concurrent establishment of the two invading species, known to have occurred frequently as casual visitors to Socorro and other islands, largely to the provision of fresh water made available as a result of human settlement. Our data show that simple comparison of island species lists compiled at intervals is an inadequate base for theories of island species turnover.
The Laying Cycle of Brown-Headed Cowbirds: Passerine Chickens?
Authors: Scott D. M. , Ankney C. Davison
Published: September 2019

We collected 270 female Brown-headed Cowbirds (Molothrus ater) in southern Ontario in 1976 to determine ovarian and oviducal growth during the breeding season and 188 female cowbirds in 1977 to estimate clutch size and the interval between clutches. Ovaries and oviducts grew rapidly in April, reached breeding size in early May, and remained at this size, without regression between clutches, until the end of the breeding season in early July. Ovaries and oviducts then regressed rapidly and by the end of July weighed about the same as those in early April. The clutch size averaged about 4.0-4.6 eggs, similar to clutch sizes of nonparasitic icterids. It varied greatly from 1 egg, in about 10% of the birds, to about 7 eggs. Two days without laying usually separated consecutive clutches, but some birds appeared to miss laying for only 1 day. Although atresia of large yolky follicles was common in birds between clutches, it did not always precede the end of a clutch. The long reproductive period without regression and the short interval between clutches are atypical of passerine reproduction. Rather, the laying cycle of cowbirds is similar to that of domestic chickens (Gallus gallus). The laying cycle of cowbirds seems adapted to a continuous supply of host nests; atresia may be related to a shortage of nests.
Additions to the Avifauna of Honduras
Authors: Marcus Mickey J.
Published: September 2019

I report specimens and sight records of 15 species new to Honduras: Mesembrinibis cayennensis, Falco femoralis, Anous minutus, Ara ambigua, Chalybura urochrysia, Baryphthengus martii, Myrmeciza exsul, Hylopezus perspicillatus, Conopias parva, Lophotriccus pileatus, Dacnis cayana, Vermivora ruficapilla, Tachyphonus delatrii, Pitylus grossus, and Sporophila schistacea. Twelve additional range extensions within Honduras are reported for species that reach their northern limit of distribution in the lowland forests of the Mosquitia region: Tigrisoma lineatum, Leucopternis semiplumbea, Ortalis cinereiceps, Ramphastos swainsonii, Myrmotherula fulviventris, Myrmotherula axillaris, Hylophylax naevioides, Phaenostictus mcleannani, Colonia colonus, Myiozetetes granadensis, Cyporhinus phaeocephalus, and Cacicus uropygialis. With the exception of Anous minutus, Falco femoralis, and Vermivora ruficapilla, all records are range extentions from the south. Some of the northward range extensions into the forests of eastern Honduras from the contiguous forests of Nicaragua were expected, but other records indicate notable range extensions. A list is provided of those species that currently reach their northernmost distribution in Nicaragua and whose presence may be expected in adjacent regions of Honduras. The extensive humid forests in the departments of Olancho and Gracias a Dios are the northernmost limits of numerous species, which may be prevented from further northward dispersal by biogeographic barriers.
Feeding-Site Selection and Foraging Strategies of American Woodcock
Authors: Rabe Dale L. , Prince Harold H. , Beaver Donald L.
Published: September 2019

Live-trapped, adult American Woodcock (Scolopax minor) were tested in a series of laboratory experiments designed to evaluate the role of soil as a proximal cue for selecting feeding sites and to investigate foraging strategies for capturing earthworms (Lumbricidae). Foraging trials were conducted in a circular arena and showed that color, which tends to be correlated with the soil types and moisture regimes preferred by earthworms, was an important proximal cue for selecting feeding sites. Woodcock captured earthworms most efficiently in areas of relatively high prey density, because they used a nonrandom search pattern following an initial capture.
The Foraging Ecology of Peruvian Seabirds
Authors: Duffy David Cameron
Published: September 2019

Most feeding by seabirds in the Peruvian Coastal Current, an upwelling of high productivity off the west coast of South America, takes place in groups. The major prey is an anchovy (Engraulis ringens), which occurs in large shoals and is exploited mainly by three species: the Peruvian Booby (Sula variegata), Peruvian Brown Pelican (Pelecanus occidentalis thagus), and Guanay Cormorant (Phalacrocorax bougainvillii). Other foraging situations have different species' compositions, and these appear to be related to the size, depth, and duration of availability of prey. Dominance interactions between species may be important in structuring flocks that are scavenging or feeding on plankton swarms. Interspecific piracy seems unimportant in flocks foraging on fish shoals. Certain species usually arrive first at new feeding situations. These species may be used as guides by other species or merely may be faster and thus reach food sources first. Studies of foraging of seabirds should be a valuable addition to the study of the distribution of birds at sea.
Nest-Site Selection by the Red-Tailed Tropicbird
Authors: Clark L. , Ricklefs R. E. , Schreiber R. W.
Published: September 2019

Red-tailed Tropicbirds (Phaethon rubricauda) nest under shrubs in loosely associated groups on Christmas Island, Central Pacific Ocean. Aggressive interactions among adults at nest sites are high; yet, large areas of superficially similar habitat contain no tropicbird nests at all. We compared physiognomic features of nest sites with those of two sets of randomly generated "nest sites" by discriminant function analysis. Of those variables measured, the number of stems within a nest space and the amount of peripheral cover influenced the tropicbirds' choice of nest sites. Differences among localities existed. Areas where tropicbirds nested had shrubs with few stems and more peripheral cover. Preferred nest sites were rare in areas other than those in which tropicbirds were nesting already. This study demonstrates the utility of the discriminant function technique in quantifying nest-site selection and nest-site availability when the appropriate null data sets are used.
Feeding Habitats of Nesting Wading Birds: Spatial Use and Social Influences
Authors: Erwin R. Michael
Published: September 2019

In an effort to relate social interactions to feeding-habitat use, I observed six species of wading birds near a major colony site in coastal North Carolina. Three spatial scales of habitat use were considered: the general orientation to and from the colony (coarsest level), the habitat "patch," and (at the finest level) the microhabitat. Departure-arrival directions of Great Egrets (Casmerodius albus), Snowy Egrets (Egretta thula), Cattle Egrets (Bubulcus ibis), Little Blue Herons (Egretta caerulea), Tricolored Herons (Egretta tricolor), and Glossy Ibises (Plegadis falcinellus) were monitored at the colony site to document coarse patterns of feeding-habitat use. Added to these data were observations made at five different wetland sites to monitor between-habitat and within-habitat patterns for the five aquatic-feeding species.

The results indicated a broad and variable use of feeding habitat over time. At the coarsest scale (i.e. orientation at the colony), diffuse patterns, influenced little by either inter- or intraspecific social interaction, were found for all species. At the next level (habitat "patch"), only one of five wetland sites was relatively consistent in attracting feeding birds, and its use increased from May to June. Few groups were seen at four of the five sites. At the one "attractive" site, the within-habitat patterns again were spatially variable over time, except for those of the abundant Snowy Egret, whose microhabitat preference was fairly consistent. Glossy Ibises and Snowy Egrets frequently formed mixed-species groups, Little Blue Herons were the least social, and Great Egrets and Tricolored Herons generally occurred in groups of less than 10 birds but rarely in groups larger than 30. The close association between Snowy Egrets and Glossy Ibises appeared to be based on a "beater-follower" relationship, wherein the probing, nonvisually feeding ibises make prey more available to the followers. In the study area, local enhancement appeared to play a more important role than did any "information-sharing" at the colony.
Occurrence and Timing of Second Clutches in Common Terns
Authors: Wiggins David A. , Morris Ralph D. , Nisbet I. C. T. , Custer Thomas W.
Published: September 2019

Eighteen pairs of Common Terns (Sterna hirundo) at three different colonies laid second clutches while still feeding young from their first broods. Seven clutches were laid before the chicks from the first brood fledged, and 11 were laid after the chicks from the first brood fledged. In each case, parents alternately fed chicks from the first brood and incubated the second clutch. Sixteen of the 18 clutches disappeared, were addled, or were deserted. Young hatched from the two other second clutches, but all chicks died or disappeared 2-4 days after hatching. We suggest that a second clutch, laid before chicks from the first brood fledged, probably results from a physiological miscue associated with chick loss from the first brood and stimulated by an unusual surplus of food. Conversely, when laid after chicks from the first brood fledge, a second clutch might function as insurance, permitting a pair to raise young late in the season if chicks from the first brood are lost. In either case, parents must partition care between eggs and chicks from the second clutch and fledged chicks from the first brood. Accordingly, the successful fledging of chicks from two broods in a single season is unlikely unless exceptionally favorable conditions occur.
Components of Variance in Measurements of Nestling European Starlings (Sturnus vulgaris) in Southeastern Pennsylvania
Authors: Ricklefs Robert E.
Published: September 2019

I report the results of experiments designed to distinguish factors affecting within-population variability in measurements of nestling European Starlings (Sturnus vulgaris). Individuals were switched among pairs of nests at the beginning of the incubation period and at the beginning of the nestling period. Variables were analyzed in a replicated (nested), three-way factorial analysis of variance to distinguish the contributions of factors associated with (1) the genotype of the embryo or composition of the egg, (2) the incubation period, and (3) the nestling period. In addition, I analyzed the correlations among growth variables within the sample as a whole and among main effects in the experimental design to search for patterns of genotypic and phenotypic interrelationship. I also related growth variables of nestlings to the size and composition of sibling eggs and to the length of the incubation period. The present experiment did not reveal any genetic or egg-quality component to within-population variation in rate of mass increase and mass asymptote achieved, length of the tarsus of fully grown nestlings, or rates of growth of the wing and outer primary feather. Similarly, the nest in which the individual was incubated had no effect on postnatal growth. The nest in which the individual was reared significantly contributed between 19 and 29% of the sums of squares in rate of mass increase, length of the tarsus, rate of increase in length of the wing, and the maximum length of the sheathed portion of the outer primary feather. Rearing nest did not have a significant effect on the mass plateau of the chick. These results, particularly the absence of some effects, are difficult to interpret, because a large proportion of the variation in several variables occurred between pairs of switched nests. These differences undoubtedly included some of the variation that might have been attributable to effects within experiments. Growth variables were weakly correlated over the entire sample, revealing little pattern of variation in postnatal growth. Over certain of the effects in the experimental design, however, particular groups of variables were strongly correlated, indicating interrelated responses of some of the growth parameters to environmental and, perhaps, genetic factors. The size of the egg had a small effect only on the mass plateau and the length of the tarsus of the chick. The composition of a sibling egg influenced only the maximum length of the sheath of the outer primary feather. The present study was somewhat weakened by small sample size and an inexplicable between-experiment effect that reduced its power to distinguish among effects of interest. The experimental design has the potential, however, to disentangle many classes of factors associated with genotype and parental care that contribute to within-population variation in phenotypic measurements.
Avian Anatomical Specimens: A Geographic Analysis of Needs
Authors: Jenkinson Marion Anne , Wood D. Scott
Published: September 2019

The anatomical inventories of Wood et al. (1982a, b) indicated that nearly one-third of the world's bird species are not represented by skeletal specimens or spirit specimens. Additionally, long series of anatomical specimens, necessary for many kinds of studies, exist for only a very few species. To encourage collectors to fill in gaps in anatomical holdings, we divided the world into 60 geographic areas, developed avifaunal lists for these, and indicated what species in each area are most critically needed as anatomical specimens. The details are given by Wood and Jenkinson (1984). Various analyses indicate that collecting efforts are most needed in the following areas: Colombia, Venezuela, Bolivia-Peru-Ecuador, Brazil-Paraguay-Uruguay, Africa (except north Africa), the Indian subcontinent, Burma, New Guinea, Madagascar, Seychelles, and the islands north of Australia (except Borneo). Although collecting efforts are especially important in those areas, specimens are needed from all sites to provide series from throughout each species' range. Curators and collectors should make new or renewed efforts to increase anatomical holdings through a variety of approaches to specimen acquisition and preparation.
Brood Parasitism in a Host Generalist, the Shiny Cowbird: II. Host Selection
Authors: Mason Paul
Published: September 2019

Host selection by brood parasitic Shiny Cowbirds (Molothrus bonariensis) was studied at two sites in Buenos Aires Province, Argentina. The eggs of the parasite are either spotted or immaculate, so host selection was studied with respect to egg type as well as to site. Immaculate eggs were rare at both sites. Cowbirds in this region prefer to parasitize nests of birds larger than themselves. This preference contrasts with that of almost all other brood parasites, and even that of Shiny Cowbirds in other parts of the species' range. One large species, the Chlk-browed Mockingbird (Mimus saturninus) was used frequently and consistently at both sites. At least two other large species (thrushes) were used at Site I, but neither was present at Site II. Cowbirds were more specialized on large hosts at Site I: only 9% of the spotted eggs were laid in nests of small birds at Site I, whereas 35% were laid in such nests at Site II. Small species, such as the Rufous-collared Sparrow (Zonotrichia capensis), were used to a greater extent at Site II than Site I (where some of the same species were not used at all). The shift to smaller hosts is probably a response to a change in the structure of the community; large host species are relatively less abundant at Site II.

Rejecter species are large, and all were parasitized while many smaller accepter species were unmolested. Surprisingly, more immaculate eggs were laid in nests where they had little chance of successful incubation, rather than in nests of accepters. No evidence suggests that host races ("gentes") are formed. To the contrary, female cowbirds laying different egg types apparently select hosts in the same manner.
Clutch Size and Fledging Success in the Turquoise-Browed Motmot
Authors: Scott Peter E. , Martin Robert F.
Published: September 2019

Clutches of 4 eggs accounted for 64-73% of all clutches laid in 3 yr by a population of Turquoise-browed Motmots (Eumomota superciliosa) in Yucatán, Mexico. The consistently high frequency of 4-egg clutches was associated with only a slight advantage in fledging success relative to clutches of 3 eggs, which ranged in frequency from 11% to 33%. Differences in number of young fledged and proportion of hatchlings fledged were not statistically significant over 3 yr or in any particular year. Clutches of 4 yielded more surviving young in 2 of 3 yr, averaging 2.02 compared to 1.71 for clutches of 3. The proportion of hatchlings that fledged was higher in broods of 3 (overall = 0.67) than in broods of 4 (overall = 0.55) in 2 of 3 yr. The proportion of hatchlings fledged from clutches of 5 (0.36) was lower over 3 yr than that fledged from clutches of 4 or 3. Approximately 40% of nestling mortality in nests that escaped predation was due to starvation. Other known causes included falls from nests and parasitism by maggots.
Differences in Susceptibility to Predation during Nesting Between Pied and Black Stilts (Himantopus spp.)
Authors: Pierce Raymond J.
Published: September 2019

The nesting success of the Pied Stilt (Himantopus himantopus leucocephalus) and the endangered Black Stilt (H. novaezealandiae) was studied for three consecutive breeding seasons (1977-1979) in New Zealand. Black Stilts had a breeding success of less than 1%, compared with over 8% for Pied Stilts. Predation by feral mammals was the main cause of nest failure for both species, but the impact was greater on Black Stilts. Direct and indirect evidence (including trapping predators) suggests that these introduced ground predators kill many chicks. Several factors made Black Stilts vulnerable, particularly their nesting along stream banks that were often frequented by predators; Pied Stilts nested in swamps where predators were few. Black Stilt chicks took up to 2 weeks longer to fledge and their foraging patterns made them more vulnerable than Pied Stilt chicks. Other factors that possibly increased predation risk of Black Stilts include nesting at times of high predator activity, solitary nesting, high site fidelity, ineffective distraction displays, and lack of a disruptive camouflage pattern in adults. Introduced ground predators probably have contributed greatly to the decline of Black Stilts. Pied Stilts have not been affected similarly, because their evolutionary past has included long exposure to ground predators.
Molt of Female Lesser Scaup Immediately Following Breeding
Authors: Austin Jane E. , Fredrickson Leigh H.
Published: September 2019

The chronology, pattern, and intensity of the molt following breeding in female Lesser Scaup (Aythya affinis) were studied from July through October 1981-1982 and in July 1984 in southwestern Manitoba. Nonbreeding females or females that were unsuccessful breeders began molt in mid-July, but females with broods delayed molt until August. The molt-intensity index was greatest during the flightless and postflightless periods. Molt persisted at low levels through the fall migratory period. Molt scores were most variable in the preflightless period. Molting began on the head, neck, and side and progressed to the belly, upper back, and chest; the lower back was the last area to molt. Feather replacement was most rapid in the wing and capital regions. The capital region and tail were the last areas in which molt was completed in fall-migratory scaup. Molt in postbreeding females probably is influenced by the length, timing, and success of breeding efforts. Individual and geographic differences in breeding chronology, habitat conditions, and postbreeding movements may contribute to variations in molt within a population of migratory scaup.
Generic Status of Euler's Flycatcher: A Morphological and Biochemical Study
Authors: Lanyon Wesley E. , Lanyon Scott M.
Published: September 2019

A concordance in the distribution of uniquely derived character states of the syrinx and of six protein coding loci confirms that euleri should be removed from the genus Empidonax and that its nearest relatives are Cnemotriccus and Aphanotriccus. A hypothesis that euleri is the sister taxon of Aphanotriccus is based on the sharing of a uniquely derived syringeal structure and two synapomorphic allozymes, and on the comparatively low genetic distance between them. A new genus, Lathrotriccus, is proposed for euleri, which differs from Aphanotriccus in its cranial morphology. The reassignment of euleri increases the desirability of obtaining anatomical specimens and tissue of griseipectus, the only remaining South American endemic in Empidonax, and of tissue of Xenotriccus, a near relative of euleri on the basis of syringeal morphology.
An Analysis of Vocal Communication in the Adult Brown Noddy (Anous stolidus)
Authors: Riska Diane E.
Published: September 2019

I analyzed vocal signals of marked adult Brown Noddies (Anous stolidus) throughout their nesting season in the Dry Tortugas, Florida from 1979 to 1982. The basic unit of the adult repertoire is a wide-band click, less than 4 msec duration, ranging in frequency from 200 to 3,300 Hz. I identified nine temporal arrangements of these clicks, which form the notes of the calls. These calls differ little in frequency range, but they differ in the mean frequency of the most intense sound energy band, in note duration, in the number of clicks per note, and in internote interval. These calls are used in different contexts, which sometimes overlap. Frequency, note duration, and internote interval do not differ between sexes. Mean frequency and note length varied among individuals for some calls. No tonal elements characteristic of calls of Brown Noddy nestlings remain in the adult repertoire.
Metabolism, Growth, and Activity in Adélie and Emperor Penguin Embryos
Authors: Bucher Theresa L. , Bartholomew George A. , Trivelpiece W. Z. , Volkman N. J.
Published: September 2019

The eggs of Adélie (Pygoscelis adeliae) and Emperor (Aptenodytes forsteri) penguins are smaller than those of large species in other orders. The incubation period in Adélie Penguins was as predicted based on egg mass, but in Emperor Penguins it was 50% longer than predicted. Although penguins have been described as semialtricial using the behavioral and morphological traits in Nice's (1962) classification, total oxygen consumption during incubation was similar to that of eggs of the same masses laid by precocial species. In both penguin species prepipping oxygen consumption was at a level predicted for precocial species.

Adélie embryos grew continuously during the last two weeks of incubation, but the relative growth rate (%/day) of both wet and dry mass decreased steadily until day 32 of incubation. From day 21 to day 31 of incubation, there was no significant change in the wet mass, dry mass, or caloric content of yolk. The mass-specific caloric content of the embryos remained constant at 5.49 kcal/g dry mass. Activity of the embryo between pipping and hatching contributed importantly to measured oxygen consumption (∼10% of the total measured during incubation, ∼20% in pipped eggs from 3 days to 1 day before hatching, and ∼25% on the day of hatching).

We suggest that the limited behavioral repertoire of hatchling penguins evolved as a response to the severity of the environment into which they hatch and because of the skilled predatory behavior that they must learn before they can feed themselves.
Population Ecology of the Long-Billed Curlew (Numenius Americanus) in Western Idaho
Authors: Redmond Roland L. , Jenni Donald A.
Published: September 2019

In western Idaho, a breeding population of Long-billed Curlews (Numenius americanus) remained relatively stable over a 7-yr period. Productivity was monitored closely from 1977 through 1979. Clutch mortality rates did not differ significantly among years, and mean clutch survival for a 32-day nesting period (4 days egg laying and 28 days incubation) was 40% for all 3 yr combined. Females laid just one clutch (usually of 4 eggs) each season, and mean clutch size was significantly smaller in 1979 than in 1977 and 1978. Estimated fledging success ranged from 0.40 in 1977 to 0.17 in 1978 and was consistently greater for females that nested early each season. Mean annual adult survival was estimated at 85% based on resightings of color-marked individuals. Limited data for subadult survival precluded complete demographic analysis. Nevertheless, given the estimates of productivity and adult survival pooled for 3 yr, survival of subadults from fledging until first breeding as 3-year-olds needed to be only 58% to maintain the stable population size observed through 1983.
Field Metabolism and Food Consumption of Savannah Sparrows during the Breeding Season
Authors: Williams Joseph B.
Published: September 2019

I applied the doubly labeled water (DLW) technique to measure rates of water flux and energy expenditure of Savannah Sparrows (Passerculus sandwichensis) during two breeding seasons on Kent Island, New Brunswick, Canada. Simultaneous to DLW measurements, I constructed time-activity budgets for territorial males, monitored nest attentiveness for incubating females, and quantified frequency of nest visitation for parents feeding young. To ascertain the relationship between brood size and adult energy expenditure, I measured the energy expenditure of adults feeding 2, 4, and 6 nestlings. There was little difference in field metabolic rates (FMR) between territorial males [161.0\pm 21.7 (SD) ml CO2/h). and males that fed 4 nestlings (157.6 ± 19.7 ml CO2/h). Incubating females expired CO2 at rates lower than males during the same time period (134.4 ± 7.9 vs. $161.0 ± 21.7 ml CO2/h but similar to rates for females feeding 4 young, the normal brood size ($134.4 ± 7.9 ml CO2/h for incubating females vs. $136.5 ± 26.9 ml CO2h for females feeding young). Incubating females expended energy at a lower rate than females making 8 or more trips to the nest per hour, the average feeding rate for females late in the nestling period. For males and females together, water influx and efflux rates averaged 17.1 ± 3.2 and 17.2 ± 3.0 ml H20/day, suggesting that birds balanced water intake against water losses. Mean daily solar radiation (MDSR; W/ m2) also influenced FMR during the nestling period. The equation ml CO2/h=172.6-0.07 (MDSR) described the relationship. When brood sizes were manipulated, parents responded by altering their frequency of nest visitation; as frequency increased, so did the FMR of females but not of males. The equation ml CO2/h =98.4 + 5.3 (mean visits/h) described the relationship. Construction of a food budget indicated that, on average, territorial males consumed 21.1 g fresh arthropods per day, while incubating females ingested 17.5 g/day or 210.0 g during the 12-day incubation period. Through the 8-day nestling period, males augmented their foraging by 75%, females by 87%, to feed a brood of 4.