bluuebunny/crossref_metadata_2025_split huggingface dataset:
Invasive grasses of sub-Antarctic Marion Island respond to increasing temperatures at the expense of chilling tolerance
Authors: Ripley Brad S , Edwardes Amy , Rossouw Marius W , Smith Valdon R , Midgley Guy F 
Published: October 2019

AbstractBackground and AimsGlobal warming has large effects on the performance and spatial distribution of plants, and increasingly facilitates the spread of invasive species. Particularly vulnerable is the vegetation of cold environments where indigenous plants selected for cold tolerance can have reduced phenotypic plasticity and associated lower capacity to respond to warming temperatures. In contrast, invasive species can be phenotypically plastic and respond positively to climate change, but at the expense of stress tolerance.MethodsWe investigate this trade-off in traits, measuring the photosynthetic response to warming, chilling tolerance and specific leaf area (SLA) of Pooid grasses. We compare this between invasive and non-invasive grasses and correlate this to their range expansions on a cold sub-Antarctic island that has warmed significantly in the past five decades. We determined whether these responses remained consistent after temperature acclimation.Key ResultsInvasive species responded strongly to warming, increasing photosynthetic rates by up to 2-fold, while non-invasive species did not respond. The response was associated with increased stomatal conductance, but not with modified photosynthetic metabolism. Electrolyte leakage and SLA were higher in invasive than in non-invasive species. Acclimation altered the photosynthetic response and invasive species responded to warm temperatures irrespective of acclimation, while non-invasive species responded only after acclimation to warm temperature.ConclusionsTraits scaled linearly with rates of range expansion and demonstrate that under sub-Antarctic conditions, anthropogenic warming over the last 50 years may have favoured species with greater capacity to respond photosynthetically to warming to the detriment of species that cannot, and negated the advantage that chilling tolerance would have conferred on endemic species in the past. This suggests that species of cold ecosystems could be particularly vulnerable to warming as selection for stress tolerance has limited their responsiveness to environmental change, while introduced invasive species may have no such limitations. We show mechanistic evidence of the physiology that underpins an apparent trade-off between warming and chilling tolerance traits.
Intraseasonal Reproductive Costs for the House Sparrow (Passer domesticus)
Authors: McGillivray W. Bruce 
Published: October 2019

Abstract
House Sparrows (Passer domesticus) near Calgary, Alberta begin breeding in early spring and continue through to late summer. High productivity from previous broods is negatively correlated with fledgling production from second and third broods. Although fat reserves may limit the ability of females to raise young, there is no concomitant drop in clutch size or in the probability of renesting. Pairs that fledge many young in a year space fledgling production evenly over the breeding season but are most productive in mid-season. The interval between fledging and the initiation of the next clutch increases with the number fledged. This delay, an indication of the physiological strain involved in rearing young, is greater for later broods and for females nesting in trees. Measures of reproductive effort (clutch size, number fledged, length of the nestling period) vary seasonally but give no indication of peaking for last broods. Thus, reproductive effort is not adjusted to parallel changes in the probability of surviving to the next breeding attempt.
Dialect Discrimination by White-Crowned Sparrows: Reactions to Near and Distant Dialects
Authors: Tomback Diana F. , Thompson Daniel B. , Baker Myron Charles 
Published: October 2019

Abstract
In Marin County, California, the dialect populations of Zonotrichia leucophrys nuttalli are contiguous, and there is little dialect mixing. The possible importance of male-male interactions in preventing dialect mixing was tested with song-playback experiments. Males of the Limantour dialect were presented the Limantour dialect, Drake or Buzzy dialects (neighboring), or Clear dialect (distant). From previous work, we predicted that Limantour males would respond with equal or more aggression to songs of immediately neighboring dialects in comparison with their own dialect but would respond at lower levels to a distant dialect. Instead, we found that Limantour males sang significantly more songs in response to the Limantour dialect than to either neighboring or distant dialects, although the response decreased with distance, as expected. These results led us to hypothesize that responses to an alien dialect may be influenced by (1) opportunity to habituate to the alien dialect, (2) recency of divergence of the two dialects, (3) recency of contact of the two dialects, and (4) sounds common in aggressive vocalizations in other contexts being also present in some song dialects but not others.
An Hypothesis concerning the Relationship of Syringeal Structure to Vocal Abilities
Authors: Gaunt Abbot S. 
Published: October 2019

Abstract
Neither the possession of large vocabularies or repertoires nor the ability to learn phonations can be precisely correlated with the structural complexity of a syrinx. Hence, some recent investigators have suggested that avian vocal plasticity arises solely from a neurological shift. A simple syrinx, i.e. one with only extrinsic musculature, is subject to certain constraints, however. Its configuration changes as a unit, and the factors responsible for modulating sounds cannot be independently varied. Thus, the temporal characteristics of sound patterns can be varied easily, but rapid juxtaposition of different modulatory patterns is difficult. Intrinsic musculature permits isolation and independent control of syringeal components and thereby simplifies control of modulations. Syringeal complexity may not be an adaptation (i.e. did not evolve under selection) for plastic vocal behavior, but it is permissive of and probably prerequisite for such behavior.
The Progress of Oriole Hybridization in Kansas
Authors: Rising J. D. 
Published: October 2019

Abstract
Specimens of Northern ("Baltimore" and "Bullock's") orioles collected at six sites in western Kansas in 1976 and 1978 are compared with specimens collected at the same sites in the mid-1960's. No changes in the location or size of the step-cline ("hybrid zone") between the two taxa are indicated by comparisons of the plumage features of the male specimens; the distribution of phenotypes of birds from sites where both Baltimore and Bullock's orioles occur is not bimodal, and, therefore, there is no indication of selection against intermediate birds. Female Bullock's-like orioles, however, are found farther east along the Cimarron River in southwestern Kansas than they were in the 1960's. The correlations between the amount of precipitation at a locality in western Kansas and the phenotype of oriole that occurs there are high (about 0.90). This suggests that precipitation per se is a factor that determines the distributional limits of these birds relative to each other. There are no recent changes, however, in the average climatic conditions in western Kansas. Perhaps the orioles present at a site in any given season are a reflection of the conditions there the previous season or two.
The analyses of size variation among samples collected in the 1970's show an east-west cline that is more-or-less congruent with that found for plumage features; at any given site, the variability in size is positively correlated with the variability in plumage. Where a diversity of oriole phenotypes occurs, there is no tendency for females to associate with males of the "same type" (i.e. Bullock's with Bullock's or vice versa); this suggests that assortative mating does not occur.
Seasonal Influence on the Strategies of Growth and Development of Canvasback and Lesser Scaup Ducklings
Authors: Lightbody Jill P. , Ankney C. Davison 
Published: October 2019

Abstract
Eggs of a seasonally early-nesting species of diving duck (Aythyini), the Canvasback (Aythya valisineria), and a late-nesting diving species, the Lesser Scaup (Aythya affinis), were collected from south-central Manitoba. Ducklings were raised in captivity so that the pattern of growth and development of both species could be examined. Rates of growth of external components were determined in order to test the hypothesis that late-nesting species (scaup) should develop the ability to fly at a younger age and gain weight more slowly than early-hatched species (Canvasback). If Lesser Scaup acquire flight earlier, we predicted that their digestive organs would grow and develop relatively more quickly than those of Canvasbacks, enabling them to process a large amount of food at a younger age. As growth rate is related to adult body size, rates of growth of the smaller Lesser Scaup were scaled to Canvasback size at the asymptote of the juvenile growth curve. Lesser Scaup fledged when they were 6 days younger than Canvasbacks, yet there was no apparent tradeoff in total body growth, as both species fledged at approximately 92% of juvenile asymptotic weight. Flight and leg muscle growth, however, did not differ statistically between species, nor did the change in water content, an indicator of tissue maturity. This is consistent with the idea that tissue maturity, and not the ability to fly, limits growth rate. As we predicted, growth of digestive organs was significantly more rapid in Lesser Scaup than in Canvasbacks. Culmen and tarsus of Lesser Scaup also grew faster than those of Canvasbacks, and we suggest this enables scaup to become efficient foragers more rapidly. The variation in growth rates between species was partially due to the difference in body size. After accounting for this, however, we found that several organs grew faster in Lesser Scaup than in Canvasbacks. Thus, the pattern of development may be influenced by the timing of nesting.
Feeding Correlates of Breeding and Social Organization in Two Galápagos Finches
Authors: Schluter Dolph 
Published: October 2019

Abstract
Several aspects of breeding and social behavior in two Galápagos finches are related to food supply. Geospiza fuliginosa is largely granivorous, and G. difficilis is largely insectivorous. Measurements show that breeding of both species occurred when arthropod abundance was high. Breeding stopped when arthropod abundance was declining but before it was low. Breeding-territory size in G. difficilis varied inversely with food supply. Territory size in G. fuliginosa was similar across sites and was not correlated with food supply. This difference between species may be attributed to differences in the effects of invertebrate and seed resources on the functional response of consumers: feeding rate of G. difficilis on invertebrates increased linearly with their supply, whereas feeding rate of G. fuliginosa on seeds was essentially independent of seed abundance. In the nonbreeding season, the granivore G. fuliginosa moved in flocks, whereas G. difficilis was more stationary and solitary. Data indicate that seed supply was temporally more variable than invertebrate abundance, and this helps account for dry-season behavioral differences between the species. Functional response and/or renewability of seeds and invertebrates may also have influenced behavior at that time.
Effect of Diet on Visceral Morphology of Breeding Wood Ducks
Authors: Drobney Ronald D. 
Published: October 2019

Abstract
Changes in Wood Duck (Aix sponsa) digestive organs reflect adaptations to accommodate changes in diet quality, metabolism, and food intake. The size of the gizzard, intestine, ceca, and liver of males decreased between fall and spring and correlated with a reduction in the fiber content of the diet. The mean size of the intestine, liver, and ceca of hens increased in response to high dietary fiber in fall and hyperphagia during laying. Decreases in the size of digestive organs in hens were associated with reduced feeding during incubation and decreased dietary fiber between fall courtship and prebreeding.
Common Terns Raise Young from Successive Broods
Authors: Hays Helen 
Published: October 2019

Abstract
In this paper I report the first instance of a pair of Common Terns (Sterna hirundo) raising young in successive clutches during one breeding season and discuss this phenomenon in relation to male and female incubation and feeding rates and to predation. Five other pairs are noted in which the female and sometimes the male incubated a second clutch while still feeding one young from their first nest.
Reproduction of Pied Flycatchers (Ficedula hypoleuca) in Good and Bad Breeding Seasons in a Northern Marginal Area
Authors: Järvinen Antero , Väisänen Risto A. 
Published: October 2019

Abstract
We studied relationships between female size, date of egg laying, clutch size, egg size, and breeding success in Pied Flycatchers (Ficedula hypoleuca) in a marginal area in northwestern Finnish Lapland (69°N). Average June temperatures in 1975-1981 were used to classify years into "good" (warm) and "bad" (cold) breeding seasons. In general, early and warm springs were followed by "good" breeding seasons: females were heavier, laying was earlier, clutches were larger and contained larger eggs, and hatching and fledging success were better than in late and cold springs. Mainly due to low nesting success in "bad" breeding seasons, the local population could not maintain itself; immigration from the south was needed. We suggest that spring weather may provide information concerning the character of the coming breeding season, which may help birds to maximize their lifetime production of young.
Recruitment and the Timing of Reproduction in Lesser Snow Geese (Chen caerulescens caerulescens)
Authors: Cooke Fred , Findlay C. Scott , Rockwell Robert F. 
Published: October 2019

Abstract
Recruitment of offspring into a breeding population of Lesser Snow Geese (Chen caerulescens caerulescens) at La Perouse Bay, Manitoba was used as a measure of reproductive success to assess the relative fitness of females who hatched their clutches early, middle, and late in the breeding season. In three of seven seasons investigated, goslings from early-hatching clutches showed significantly greater recruitment rates than their middle- or late-hatching counterparts. No significant differences in recruitment rates were detected in the other four seasons, although early-hatching clutches showed numerically higher recruitment rates in three of these seasons. There is, therefore, some indication of directional selection for early breeding. This conclusion contrasts with that drawn by Cooke and Findlay (1982), who, using fledging success as a measure of reproductive fitness, showed that females whose clutches hatched in the middle period had the highest fitness and concluded that the population was being exposed to stabilizing selection for synchronization. The discrepancy between these results and those presented in this paper indicates that conclusions concerning the action of selection in natural populations depend heavily upon the stage of the life cycle during which reproductive success is estimated. As such, evolutionary biologists must be cautious of relying too heavily on measures taken too early in the life of the organism.
Bioenergetics of Egg Production by Female House Sparrows
Authors: Krementz David G. , Ankney C. Davison 
Published: October 2019

Abstract
To determine the daily and total energy expenditures of breeding female House Sparrows (Passer domesticus), we collected 276 females near London, Ontario between April 1981 and May 1983. Protein and fat content of developing follicles, eggs, and oviducts were determined and converted into their energy equivalents. Eight days were required to develop and lay a modal clutch of 4 eggs. Fat energy requirements were not estimable accurately because total body fat did not decline linearly over the egg production period; therefore, energy requirements were estimated as a range. Based on a 4-egg clutch, the maximum daily costs of reproduction, 16.5-17.6 kJ/day, equalled 44-47% of a female's standard metabolic rate. We estimate that daily costs very less than 10% for other clutch sizes (3 or 5). The total energy demand of reproduction was 66-71 kJ. Protein requirements comprised 59-63% of the total costs and were apportioned among oviduct (5-6%), yolk protein (17-19%), and albumen (36-39%). Fat requirements accounted for the remaining 37-41% of total costs. Based on our estimates of energy needed for reproduction, and on other evidence, we suspect that egg production by House Sparrows is not constrained by energy acquisition.
Seasonal Aspects of the Diet of Bonaparte's Gulls (Larus philadelphia) in the Quoddy Region, New Brunswick, Canada
Authors: Braune Birgit M. 
Published: October 2019

Abstract
During July-December 1978-1984, Bonaparte's Gulls (Larus philadelphia) on annual migration through the Quoddy region off New Brunswick, Canada, fed on fish, euphausiids, insects, and other marine invertebrates (mainly polychaetes and amphipods) in varying proportions as the summer and autumn progressed. The seasonal variation in the diet was related directly to food availability, which, in turn, was dictated by natural cycles of prey in the region. The frequency with which plastic particles were found in the stomachs also had a statistically significant seasonal trend. Fish provided the largest energy contribution (75-91%) to the diet at all times in the region. There was no significant difference between diets of juvenile and adult birds.
Activity Budgets and Foraging Ranges of Breeding Common Murres
Authors: Cairns D. K. , Bredin K. A. , Montevecchi W. A. 
Published: October 2019

Abstract
We used electronic activity recorders to measure flight time, dive time, and time on the water of breeding Common Murres (Uria aalge). During both incubation and chick rearing, about 90% of birds' time away from the colony was spent on the water or diving and 10% was spent flying. The proportion of flight time did not vary with trip duration. During chick rearing, 13.6% of time away from the colony was spent diving, and the proportion of time spent diving tended to decrease with trip duration. Potential foraging ranges calculated from flight times during individual foraging trips showed a concave frequency distribution, and median potential ranges were 37.8 km for incubating birds and 5.4 km for chick-rearing birds. The use of electronic recorders to measure time budgets has broad applications for seabird energetics and foraging ecology and for the assessment of prey availability and abundance.
Influence of Population Size on Habitat Use by Territorial Male Red-Winged Blackbirds in Agricultural Landscapes
Authors: Clark Robert G. , Weatherhead Patrick J. 
Published: October 2019

Abstract
Fretwell and Lucas's (1970) model relating settling patterns and habitat suitability was tested by examining the distribution among habitats of male Red-winged Blackbirds (Agelaius phoeniceus) at relatively low (26 males/km2 in 1978)a nd high (45 males/km2 in 1979)overall population densities. Wetlands and hayfields were identified as the most suitable breeding habitats on the basis of habitat selection patterns of territorial males and other evidence, whereas forest, cropland, and human-occupied areas generally were avoided. Some "packing" of males into hayfields occurred when population level increased, but the greatest changes were recorded from less suitable habitats. Occupancy of wetlands and hayfields remained relatively stable. These results were in general accordance with predictions from Fretwell and Lucas's model, but their model did not account for some aspects of spacing behavior. This is because habitat imprinting, site fidelity, and chance events, in addition to territorial behavior, likely contributed also to the spacing patterns of male Red-winged Blackbirds observed.
Is Courtship Intensity a Signal of Male Parental Care in Red-Winged Blackbirds (Agelaius phoeniceus)?
Authors: Yasukawa Ken , Knight Richard L. , Skagen Susan Knight 
Published: October 2019

Abstract
We studied Red-winged Blackbird (Agelaius phoeniceus) behavior in marsh and prairie habitats to determine whether courting males provide cues of their nest defense, whether females prefer males that defend nests vigorously, and whether male nest defense affects nest success. We found no evidence that courtship behavior provides cues of male nest defense, or that females prefer males that court intensely. We found evidence that females nesting in marshes prefer males that defend nests intensely, but no evidence that intensely defending males in the prairie habitat achieve high nest success. We found differences, however, between marsh and prairie habitats that suggest a coarse-grained relationship between male parental quality and female choice of mate in this species.
Genic Population Structure and Gene Flow in the Northern Flicker (Colaptes auratus) Hybrid Zone
Authors: Grudzien Thaddeus A. , Moore William S. , Cook J. Richard , Tagle Danilo 
Published: October 2019

Abstract
The Yellow-shafted Flicker (Colaptes auratus auratus) and Red-shafted Flicker (C. a. cafer) form a stable, narrow hybrid zone on the western Great Plains of North America. Allozyme data were obtained from 31 structural gene loci for 33 samples representing 246 Northern Flickers from throughout the Great Plains. Flickers were approximately equivalent to other birds in terms of proportion of polymorphic loci (P̄ = 0.207) and average heterozygosity (H̄ = 0.056). There was no concordant variation between plumage characters and allelic frequencies.
Gene-diversity analysis indicated that 92.5% of the genic variation occurred as within-deme heterozygosity(GD= 0.925),a pproximately 7% occurred among individual demes( GST= 0.07), and only 0.9% occurred among major river drainages (GST = 0.009). Even less diversity was found amongp arentala nd hybrid groups( GST= 0.002).T here is substantiaal llozymics tructuring of the Northern Flicker speciesp opulation, but the structuringis not associated with the hybrid zone, and there is, at most, very weak structuring into riparian zones of habitat.
The electrophoretic data support the inference that gene flow among Northern Flicker populationsis high (Nm = 1.9-4.4/generation).I f the high gene-flowe stimatesa recorrect, then geographicasl electiong radientsw ould be the most likely mechanismm aintaining the narrow hybrid zone of plumage and morphometric traits.
Evidence of Former Allopatry of the Two Color Phases of Lesser Snow Geese (Chen caerulescens caerulescens)
Authors: Cooke F. , Parkin D. T. , Rockwell R. F. 
Published: October 2019

Abstract
Plumage color is distributed clinally in the Gulf Coast population of the dimorphic Lesser Snow Goose (Chen caerulescens caerulescens); the white phase predominates in the west, and the blue phase in the east. A similar distribution occurs in the breeding colonies of this population. Historical evidence, stretching back to the mid-18th century, shows that the two phases were almost allopatric until the third decade of the 20th century. Allozyme variants at 6 loci also support the conclusion that the morphs were until recently two distinct taxa. The recent merging of the taxa probably is due to a change in winter feeding habits that allowed birds of both morphs to meet in the rice-growing areas of inland Texas and Louisiana. Because pair formation occurs at this time, this change permitted gene flow to occur between the morphs. There is no evidence of reduced fitness among mixed pairs, and interbreeding among the morphs is common. We know of no other case of a historically documented merging of two formerly allopatric taxa of birds where interbreeding is so widespread and where there is no evidence of reduced fitness of the hybrids.