bluuebunny/crossref_metadata_2025_split huggingface dataset:
Slowly but surely: gradual diversification and phenotypic evolution in the hyper-diverse tree fern family Cyatheaceae
Authors: Loiseau Oriane , Weigand Anna , Noben Sarah , Rolland Jonathan , Silvestro Daniele , Kessler Michael , Lehnert Marcus , Salamin Nicolas 
Published: September 2019

Abstract

Background and Aims
The tremendously unbalanced distribution of species richness across clades in the tree of life is often interpreted as the result of variation in the rates of diversification, which may themselves respond to trait evolution. Even though this is likely a widespread pattern, not all diverse groups of organisms exhibit heterogeneity in their dynamics of diversification. Testing and characterizing the processes driving the evolution of clades with steady rates of diversification over long periods of time are of importance in order to have a full understanding of the build-up of biodiversity through time.

Methods
We studied the macroevolutionary history of the species-rich tree fern family Cyatheaceae and inferred a time-calibrated phylogeny of the family including extinct and extant species using the recently developed fossilized birth–death method. We tested whether the high diversity of Cyatheaceae is the result of episodes of rapid diversification associated with phenotypic and ecological differentiation or driven by stable but low rates of diversification. We compared the rates of diversification across clades, modelled the evolution of body size and climatic preferences and tested for trait-dependent diversification.

Key Results
This ancient group diversified at a low and constant rate during its long evolutionary history. Morphological and climatic niche evolution were found to be overall highly conserved, although we detected several shifts in the rates of evolution of climatic preferences, linked to changes in elevation. The diversification of the family occurred gradually, within limited phenotypic and ecological boundaries, and yet resulted in a remarkable species richness.

Conclusions
Our study indicates that Cyatheaceae is a diverse clade which slowly accumulated morphological, ecological and taxonomic diversity over a long evolutionary period and provides a compelling example of the tropics as a museum of biodiversity.
Plants are intelligent, here’s how
Authors: Calvo Paco , Gagliano Monica , Souza Gustavo M , Trewavas Anthony 
Published: September 2019

AbstractHypothesesThe drive to survive is a biological universal. Intelligent behaviour is usually recognized when individual organisms including plants, in the face of fiercely competitive or adverse, real-world circumstances, change their behaviour to improve their probability of survival.ScopeThis article explains the potential relationship of intelligence to adaptability and emphasizes the need to recognize individual variation in intelligence showing it to be goal directed and thus being purposeful. Intelligent behaviour in single cells and microbes is frequently reported. Individual variation might be underpinned by a novel learning mechanism, described here in detail. The requirements for real-world circumstances are outlined, and the relationship to organic selection is indicated together with niche construction as a good example of intentional behaviour that should improve survival. Adaptability is important in crop development but the term may be complex incorporating numerous behavioural traits some of which are indicated.ConclusionThere is real biological benefit to regarding plants as intelligent both from the fundamental issue of understanding plant life but also from providing a direction for fundamental future research and in crop breeding.
Taxonomy, Distribution, and Evolution of Golden Plovers (Pluvialis dominica and Pluvialis fulva)
Authors: Connors Peter G. 
Published: September 2019

Abstract
A discriminant function analysis of specimen measurements separates 96% of two forms of Lesser Golden Plover in breeding plumage, previously described as subspecies. The forms breed sympatrically in northwest Alaska and are not isolated by habitat, but the incidence of specimens phenotypically intermediate between two forms is no higher there than in areas of allopatry. The absence of a cline of intergrades or of a hybrid zone indicates that the forms are reproductively isolated through assortative mating and are separate species. To explain the process of speciation in these very similar forms, I propose that the evolution of genetically controlled and markedly different migration routes (Pluvialis dominica to South America and Pluvialis fulva to the central and western Pacific and Indian oceans) during Pleistocene glacial isolation may have selected against hybrids during subsequent secondary contact of populations. This would leat to adaptations in behavior and plumage, such as the difference in male undertail coverts reported here, that would produce assortative mating and reproductive isolation in sympatry. Thus, the requirements of migration and winter range drive the process of speciation.
Clutch Size, Reproductive Success, and Organochlorine Contaminants in Atlantic Coast Black-Crowned Night-Herons
Authors: Custer Thomas W. , Hensler Gary L. , Kaiser T. Earl 
Published: September 2019

Abstract
In 1979, we gathered clutch-size and reproductive-success data on Black-crowned Night-Herons (Nycticorax nycticorax) nesting in three New England and two North Carolina colonies. In 1975, we gathered similar data from one of the New England and one of the North Carolina colonies. Latitudinal differences in clutch initiation were not evident. Mean clutch size was larger in the New England than in the North Carolina colonies. Mean clutch size was smaller in late nests from one New England colony studied in both years and another New England colony studied in 1979; seasonal trends in clutch size for other colonies were not found. In 1979, nest success was greater in two New England colonies than in one North Carolina colony. Within-season differences in nest success occurred but were inconsistent among colonies. In the four instances where statistical comparisons could be made, larger clutches were more successful than smaller ones in two colonies; large and small clutches had similar success in two other colonies. One egg was collected from each of several nests in each colony in 1979 for organochlorine contaminant analysis, and the fate of the remaining eggs was recorded. Concentrations of DDE and PCBs did not differ with clutch size; concentrations of PCBs were lower, however, in eggs laid late in the season. Although the data suggest an effect of DDE on hatching success in the northern more contaminated colonies, the impact of environmental contaminants on overall reproductive success appears to be minimal.
Sexual Roles in the Dot-Winged Antwren (Microrhopias quixensis), a Tropical Forest Passerine
Authors: Greenberg Russell , Gradwohl Judy 
Published: September 2019

Abstract
Dot-winged Antwrens maintain long-term pair bonds on year-long territories in tropical forests and woodland of Central and South America. Pairs partition breeding-related activities nearly equally. Like other antbirds (Formicariidae), both sexes incubate and brood. Both sexes participate equally in territorial maintenance behavior, which primarily involves active border displays. Initial investment in offspring is possibly equalized by long-term nuptial feeding of females by males. Overall, both sexes contribute equally to nestling care, although considerable variation is observed between nests, much of which probably results from variation in the foraging ability of parents. Females feed young consistently less often than do males during the early part of the nestling period and may be recovering from depletion of reserves resulting from egg production. In most pairs females bring more spiders than do males. This difference in prey type is unexpected, because the pair forages close together in the same microhabitat and their bill size is similar. Pairs are distinct in their interactions: some pairs have a rigid feeding order, and others do not.
Age-Related Mortality in a Wintering Population of Dunlin
Authors: Kus Barbara E. , Ashman Philip , Page Gary W. , Stenzel Lynne E. 
Published: September 2019

Abstract
Despite considerable evidence that juvenile shorebirds experience significantly higher annual mortality rates than adults, identification and quantification of the sources of mortality have received little attention. We found that the proportion of juvenile Dunlins (Calidris alpina) in the kills of a Merlin (Falco columbarius) one winter at Bolinas Lagoon, California was greater than the proportion of juveniles in the lagoon's winter population. This is evidence that raptor predation may be one of the factors contributing to the age differences in annual mortality rates of shorebirds. We suggest that the greater vulnerability of juveniles to predation by the Merlin may be caused by age-related differences in Dunlin flocking behavior.
Growth Energetics of Nestling Northern Gannets (Sula bassanus)
Authors: Montevecchi W. A. , Ricklefs R. E. , Kirkham I. R. , Gabaldon D. 
Published: September 2019

Abstract
We describe the energetics of postnatal growth and development of wild and captive Northern Gannet chicks. For 14 chicks 0-9 weeks old, a 24-week immature, and a breeding female, we determined water, lipid, and nonlipid content. During the 13-week nestling period, mass increased over 40-fold. Accumulation of lipid caused the energy density of chicks to increase steadily through 9 weeks. Lipid eventually accounted for about 60% of energy in tissues. Two captive chicks grew at rates comparable to wild young and consumed, on average, about 24 kg of fish containing 190,000 kJ during the nestling period. The energy density of chick guano was 13.3 Â± 0.8 kJ/g. Estimated metabolizable energy (ME) rose rapidly from 952 kJ during week 1 to 19,318 kJ during week 6, after which ME fluctuated between about 9,000 and 16,400 kJ/week. During week 1, the growth increment (GI) was 801 kJ; GI increased sharply to 9,667 kJ during week 4 and peaked at 12,711 kJ in week 7. Net growth efficiency was 49% to 8 weeks of age and 33% to fledging at 13 weeks. The food requirement of the gannet population of Newfoundland is estimated.
Flight Speed and Directional Responses to Wind by Migrating Canada Geese
Authors: Wege Michael L. , Raveling Dennis G. 
Published: September 2019

Abstract
We monitored headings, flight speeds, and time of flight of nine transmittertagged giant Canada geese (Branta canadensis maxima) during 10 different autumn migration flights during which data on wind directions and speeds were also available. Destination of these individuals was known because of previous observations of the same birds. This enabled us to evaluate their headings with respect to wind drift. As the magnitude of the following component of the wind increased, air speeds of migrating geese declined while ground speeds were not significantly changed. Therefore, the cost of transport over the ground, and probably metabolic rate, were minimized. Headings of migrant geese varied systematically and significantly with wind direction, but track directions did not deviate significantly from the goal direction. Thus, the geese compensated for wind drift. Visual reference to landmarks may have been the cue used to correct for drift, as weather conditions were such that geese could see the ground.
Why Does Intensity of Avian Nest Defense Increase During the Nesting Cycle?
Authors: Knight Richard L. , Temple Stanley A. 
Published: September 2019

Abstract
Theoretical models predict that intensity of avian nest defense should increase with age of the offspring. Empirical observations conforming with this prediction have been taken as support for these models. We here present a new explanation for the observed correlations between offspring age and level of nest defense. We propose that increased intensity of nest-defense behavior is largely a result of the methods used by the researchers who made the observations. We suggest that when an observer repeatedly visits or brings a potential nest predator to a nest, nest-defense behavior of parents is modified by positive reinforcement and loss of fear. We tested this hypothesis by measuring nest-defense behavior of female American Robins (Turdus migratorius) and male and female Red-winged Blackbirds (Agelaius phoeniceus). The tests were performed at nests visited only once during different stages of the nesting cycle and at a group of nests visited repeatedly from initiation of incubation to fledging. Nest-defense intensity (as measured by call rates, closest approach to the predator, and numbers of dives and strikes) of robins and blackbirds at nests visited once, in most cases, did not increase through the nesting cycle. At nests visited repeatedly through the nesting cycle, intensity of nest defense by both robins and blackbirds, in many cases, increased significantly. In addition to intensity of nest defense increasing at multiple-visit nests, we observed higher proportions of birds at these nests performing nest-defense behaviors than at single-visit nests.
Body Size and Condition, Timing of Breeding, and Aspects of Egg Production in Eastern Kingbirds
Authors: Murphy Michael T. 
Published: September 2019

Abstract
Variation in timing of breeding in Eastern Kingbirds (Tyrannus tyrannus) was correlated only weakly with external morphological characters, but was correlated positively and significantly with estimates of body size based on measurements of skeletons and muscle weights. Small females apparently held a reproductive advantage in being able to mobilize resources for reproduction before large females. Egg weight was independent of all measures of female size, but was directly and significantly (P = 0.03) correlated with standard flight muscle weight, a relative index of body condition. Egg size was thus a function more of female body condition than size.
On average, shell, yolk, and albumen comprised 5.6%, 21.9%, and 72.5%, respectively, of fresh egg weight. Dry albumen and dry shell increased proportionately with fresh egg weight, but dry yolk did not. Total protein, lipid, and energy of fresh eggs all increased proportionately with weight. Comparison of egg composition and standard flight muscle weight of laying females indicated moderate positive, although nonsignificant, correlations between body condition and measures of egg quality, especially lipid content. Based on post-egg-laying body composition and nutrient requirements for the production of one egg, it appeared that most females probably could have laid an additional egg almost solely from body reserves. Clutch size thus appears to be independent of body condition.
Olfactory Sensitivity of the Turkey Vulture (Cathartes aura) to Three Carrion-associated Odorants
Authors: Smith Steven A. , Paselk Richard A. 
Published: September 2019

Abstract
The Turkey Vulture (Cathartes aura) is generally thought to rely on olfactory cues to locate carrion. Because vertically rising odorants are dispersed rapidly by wind turbulence, we predict that Turkey Vultures should be highly sensitive to these chemicals to detect them at foraging altitudes.
Olfactory thresholds to three by-products of animal decomposition (1× 10-6 M for butanoic acid and ethanethiol, and 1× 10-5-5 M for trimethylamine) were determined from heart-rate responses. These relatively high thresholds indicate that these odorants are probably not cues for foraging Turkey Vultures. Odorant thresholds, food habits of Turkey Vultures, and the theoretical properties of odorant dispersion cast some doubt on the general importance of olfaction in food location by this species.
Extensive Protein Similarity of the Hybridizing Chickadees Parus atricapillus and P. carolinensis
Authors: Braun Michael J. , Robbins Mark B. 
Published: September 2019

Abstract
Starch gel electrophoresis of proteins was used to assess genetic differentiation and introgression across a contact zone between Parus atricapillus and P. carolinensis. Little or no differentiation was found at 35 presumed genetic loci, even between distantly allopatric population samples. Nei's (1978) genetic distance (D) was ≤0.001 for all comparisons. In contrast, Parus gambeli, another chickadee known to hybridize with atricapillus, was well differentiated at 3 loci (D ≈ 0.065). While the data suggest that atricapillus and carolinensis are closely related, they do not allow conclusions on the extent of introgression across the contact zone. The implications of these data are discussed in the light of the emerging pattern of isozyme variation in birds.
Reidentification of “Phalacrocorax” Subvolans Brodkorb as the Earliest Record of Anhingidae
Authors: Becker Jonathan J. 
Published: September 2019

Abstract
The putative cormorant Phalacrocorax subvolans Brodkorb 1956, from the early Miocene of Florida, is moved from the Phalacrocoracidae to the Anhingidae and should be known as Anhinga subvolans (Brodkorb 1956). This species is the earliest known anhinga and demonstrates that the family Anhingidae has been present in North America for at least 18 million years. It has been at least 30 million years since the Anhingidae and the Phalacrocoracidae shared a common ancestor.
Interseasonal and Intersexual Resource Partitioning in Hairy and White-Headed Woodpeckers
Authors: Morrison Michael L. , With Kimberly A. 
Published: September 2019

Abstract
Foraging behavior in the closely related Hairy (Picoides villosus) and White-headed (P. albolarvatus) woodpeckers was examined in an area of sympatry to evaluate interseasonal and intersexual resource use. Similar foraging heights were observed for each species-sex sample during summer, but significant differences were evident during winter. Male and female White-heads maintained similar relative foraging heights between seasons, whereas male and female Hairies foraged relatively higher during winter. Use of tree species differed significantly for each class between seasons, except for male Hairies. Differences in foraging substrates and tree health also were noted interseasonally. All foraged at similar times of day during summer, but negative relationships occurred between times of foraging during winter; foraging times were significantly different between male Hairies and White-heads.
A general trend toward decreased overlap in foraging behaviors during winter was a reflection of concentration of foraging activities on live incense cedar (Calocedrus decurrens), especially by female White-heads. This change apparently was due to the presence of an abundant and accessible prey (incense cedar scale, Xylococculus macrocarpae) on cedar. Behavioral shifts in foraging activities may be related to the differential ability to extract prey as a function of bill morphology; such an idea can be extended to intersexual as well as interseasonal considerations. Thus, segregation of foraging activities in these two woodpecker species may be attributed to morphological differences and habitat complexity rather than to competitive interactions dictated by resource limititions.
Why Are Waxwings “Waxy”? Delayed Plumage Maturation in the Cedar Waxwing
Authors: Mountjoy D. James , Robertson Raleigh J. 
Published: September 2019

Abstract
Cedar Waxwings (Bombycilla cedrorum) often have their secondaries tipped with red waxlike appendages, but a plausible hypothesis for the function of these tips has not been presented. Both males and females may have such tips, but second-year birds normally have none or only a few. This appears to be the first described instance of a passerine species to show distinctive delayed plumage maturation in both sexes. We found that waxwings mated assortatively with respect to the number of tips on the secondaries of the birds. Pairs of older birds (with high tip index scores) tended to nest earlier than younger (low tip index) birds. Older birds also had larger clutch/brood sizes and fledged more young. We suggest that the waxlike tips function as signals of age and status and that some combination of mate choice and competition for mates results in the observed assortative mating. Of the hypotheses proposed to explain the adaptive significance of delayed plumage maturation, two (the female-mimicry and cryptic hypotheses) are not confirmed in the case of the Cedar Waxwing, while the status-signaling hypothesis appears to offer the best explanation for the occurrence of delayed plumage maturation in this species.
Natal and Breeding Dispersal in House Wrens (Troglodytes aedon)
Authors: Drilling Nancy E. , Thompson Charles F. 
Published: September 2019

Abstract
We studied the natal and breeding dispersal of yearling and adult House Wrens (Troglodytes aedon) for 7 yr in central Illinois. The forested study areas contained 910 identical nest boxes placed in a grid pattern. On average 38.1% (n = 643) of the adult males and 23.3% (n = 1,468) of the adult females present in one year returned the next; 2.8% (n = 6,299) of the nestlings that survived to leave the nest returned each year. Adult male (median distance = 67 m) and adult female (median = 134 m) breeding dispersal was less than yearling male (median = 607.5 m) and yearling female (median = 674 m) natal dispersal. Females that returned had produced more offspring the previous season than had nonreturning females, and females that successfully produced at least one chick in their last nesting attempt of the previous season moved shorter distances than did unsuccessful females. There were, however, no consistent differences between returning and nonreturning females in two other measures of reproductive success. Females that were unsuccessful in their last breeding attempt of the previous year were more likely to be successful in their next attempt if they moved two or more territories than if they did not move. Reproductive success did not affect the likelihood that a male would return nor the distance that he moved. The success of subsequent nesting attempts by males was also not related to the distance moved.
Inbreeding avoidance may explain differences between breeding and natal dispersal, but it does not explain the lack of difference in dispersal of yearling females and males. Differences between adult and yearling dispersal are best explained by advantages accruing to adults that remain near former breeding sites and by the necessity for yearlings to move farther because of their late return from the wintering grounds. The advantages for adults to reoccupy previous breeding sites are counterbalanced, especially in females, by advantages associated with moving after breeding failure.
Song Similarity between Neighboring American Redstarts (Setophaga ruticilla): A Statistical Analysis
Authors: Shackell N. L. , Lemon R. E. , Roff D. 
Published: September 2019

Abstract
We examined the hypothesis that territorial American Redstart (Setophaga ruticilla) males are geographically randomly distributed with respect to structure of the single song used predominantly before nesting. Present methods to assess the degree of similarity of song between neighboring birds are often inadequate because they do not give the level of statistical significance. We present a computer method to generate the appropriate null distribution from which the level of significance can be determined. We found statistically significant correlations between neighbors primarily in the last and penultimate discrete vocal items (phones) of the song. There were also important differences between the 2 samples.