bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth and Development of Homeothermy in Nestling European Shags (Phalacrocorax Aristotelis)
Authors: Østnes Jan Eivind , Jenssen BjØrn Munro , Bech Claus , Nettleship D. 
Published: September 2019

AbstractEuropean Shag (Phalacrocorax aristotelis) nestlings were studied on a small island off the coast of central Norway. Increase in body mass (BM) with age (t, days) was described by the logistic equation: BM = 1,622 g/[1 + e−0.172(t−19.9)]. All growth parameters measured (body mass, and length of tarsus, wing and head) showed highest relative growth rate when the nestlings were 5–10 days old, that is, before the nestlings had achieved homeothermy. An incipient endothermic response was noted when nestlings were 9 days old, and they became homeothermic at ages of 15–18 days. Respective mass-specific resting metabolic rates for nestlings 0, 15, and 45 days old were 47, 261, and 147% of the predicted value for adult nonpasserine birds of similar body masses. Mass-specific minimal thermal conductance decreased from 366% of predicted adult value at hatching, to 220% of that predicted when nestlings were 21 days old. For nestlings 15 days old, the factorial metabolic scope (resting metabolic rate/peak metabolic rate) was only 1.5, but that increased rapidly thereafter. Rapid increase in the mass-specific RMR and decrease in minimal thermal conductance is suggested to contribute importantly to improve homeothermic ability during the first two weeks of the developmental period. At hatching, leg and pectoral muscles constituted 5.3 and 2.2%, respectively, of total wet body mass. Relative leg-muscle mass increased rapidly and had almost reached adult proportions when the nestlings were 25–30 days old. In contrast, pectoral-muscle mass increased in an almost direct proportion to the body mass during the first 30 days of the growth period, and increased rapidly thereafter. At hatching, the water fraction (water content/lipid-free wet mass) was significantly lower in the leg than in the pectoral muscles (0.920 vs. 0.931). The water fraction of leg muscles also remained lower during the entire growth period. Judging from the proportionately greater mass and higher degree of maturity of the leg compared to pectoral muscles, the former would seem to be the main site of cold-induced heat production during early development of homeothermy in European Shag nestlings.
Age at First Breeding and Natal Dispersal in a Declining Population of Cassin's Auklet
Authors: Pyle Peter , Nettleship D. 
Published: September 2019

AbstractAge of first breeding (AFB) and natal dispersal distance (NDD) were investigated relative to proximate and ultimate factors in 276 known-age Cassin's Auklets (Ptychoramphus aleuticus) breeding during 1981–1999 on Southeast Farallon Island, California. Breeding density in 446 study boxes declined significantly during the period 1987–1999, confirming other information indicating a long-term decline (since at least the 1970s) in the population. Mean AFB was 3.34 years when sexes were combined, ranging from 2–10 (mean 3.36) years in females and 2–9 (mean 3.36) years in males. AFB showed a significant linear increase with decreasing colony density, suggesting that increased stress on the entire population, such as that caused by decreasing food availability, may have prevented younger birds from attaining breeding condition at an early age. Median NDD was 8.84 m, ranging from 0–448.7 m; two individuals of each sex recruited into their natal boxes. NDD showed a significant linear increase with decreasing breeding density but no significant linear or curvilinear correlations with mate fidelity, annual reproductive success, or lifetime reproductive output. A significant proportion (66.9%) of movements after recruitment (breeding dispersal) resulted in closer proximity to the natal site. Thus, although natal philopatry was strongly developed in the Cassin's Auklet, it did not seem to be adaptive. Those paradoxical results suggest that selective equilibrium may be acting on natal philopatry in response to the population decline: a low-philopatry, low-cost (later breeding and increased survival) strategy has become increasingly adaptive in Cassin's Auklets, explaining increases in AFB and NDD with the declining breeding densities. The lack of sex-specific effects on AFB and NDD suggests that an even sex-ratio and roughly equal roles in reproduction among Cassin's Auklets exists on Southeast Farallon Island, and that inbreeding avoidance may be counter-balanced by relatively low mate fidelity in this species.
Wood Thrush Movements and Habitat Use: Effects of Forest Management for Red-Cockaded Woodpeckers
Authors: Lang Jason D. , Powell Larkin A. , Krementz David G. , Conroy Michael J. 
Published: September 2019

Abstract
We monitored adult and juvenile breeding-season movements and habitat use of radio-tagged Wood Thrushes (Hylocichla mustelina) at the Piedmont National Wildlife Refuge, central Georgia, USA. We investigated the effects that management for Red-cockaded Woodpeckers (Picoides borealis), thinning and burning >30 year old loblolly pine (Pinus taeda) habitat, had on Wood Thrushes, a ground-foraging and midstory-nesting species. Adult Wood Thrush pairs regularly moved long distances between nesting attempts (range 1 to 17,388 m). The only experimental effect we found on adult movements was a decrease in weekly emigration rates (Ψ) from thinned and burned compartments after silvicultural management. Adult males preferred riparian hardwoods with sparse to moderate cover and those preferences increased following management. Juveniles remained near their nest site (x̄ = 177 m, SE = 113) for an average 24 days (SE = 6.3), and then dispersed a mean 2,189 m (SE = 342). Before dispersal, juveniles preferred upland hardwood–pine mixed habitat (P < 0.05) with moderate overstory cover (P < 0.05). We found no management effects on dispersal distances or predispersal habitat use. However, juveniles from thinned and burned compartments dispersed to hardwood habitats with dense cover, whereas birds from control compartments dispersed to pine-dominated habitats with sparse cover. All juveniles dispersed to areas with habitat similar to what they used before dispersal. Small-scale thinning and burning for Red-cockaded Woodpeckers may have had little effect on Wood Thrush habitat use and movements because typical movements were often larger than the scale (stand or compartment) targeted for management.
Maternal Condition and Nestling Sex Ratio in House Wrens
Authors: Whittingham Linda A. , Valkenaar Stacy M. , Poirier Nicole E. , Dunn Peter O. 
Published: September 2019

AbstractParents are expected to vary the sex ratio of their offspring in relation to the sex-specific fitness benefits. However, benefits of producing sex-biased broods may be dependent on condition of the female. For example, mothers in good condition could achieve greater fitness if they produced high-quality sons, whereas, mothers in poor condition would gain more by producing daughters rather than poor-quality sons. As a consequence, we would expect to see a relationship between female condition and sex ratio of offspring. We examined effect of maternal condition on nestling condition and sex ratio in the House Wren (Troglodytes aedon). Overall sex ratio of nestlings in the population was not biased, but females in better condition produced relatively more sons. Overall positive relationship between female condition and proportion of male offspring was due to second broods, which were significantly male-biased and more likely to be produced by females in good condition. Females in better condition also tended to provision young more often and produced both male and female nestlings in better condition. Polygyny and extrapair mating are common in House Wrens. If males in good condition are more likely to be successful breeders as adults, then it may benefit mothers in good condition to produce more sons.
Manakins (Pipridae) in Second-Growth and Old-Growth Forests: Patterns of Habitat Use, Movement, and Survival
Authors: Blake John G. , Loiselle Bette A. 
Published: September 2019

AbstractWe used capture and recapture data (1985 to 1994) to examine seasonal variation in habitat use, movements within and among habitats, and survival rates of manakins (Manacus candei, Corapipo altera, Pipra mentalis, P. pipra) in northeastern Costa Rica. Manakins were captured in young and old second-growth woodlands in the lowlands and in old-growth forest at approximately 50, 500, and 1,000 m. Manakin species differed in their use of habitats, with old-growth forest species showing large and predictable seasonal variation in capture rates. Corapipo capture rates in lowland (nonbreeding) habitats were greater during the wet season than during the dry season and were greater in old-growth forest than in second growth. Capture rates at 500 m were higher in the dry season. Pipra mentalis capture rates were high in second growth and old growth. Capture rates were higher in the wet season and were correlated with capture rates of Corapipo, indicating that at least some individual P. mentalis migrate along the elevational gradient. P. pipra capture rates were highest at 1,000 m; few individuals descended to lowlands in the wet season. Manacus capture rates were highest in young second growth and did not vary between wet and dry seasons. Use of second-growth habitats by species typically associated with old-growth forests illustrates the value of maintaining a mosaic of habitats to accommodate seasonal changes in use of habitats. Contrary to expectations based on lek mating systems, there was little evidence that movements within habitats (i.e. recapture distances) varied between sexes. Yet, recapture percentages were higher in all species for adult females than males. Adult survival rates were ∼0.75 for Manacus in young second growth, 0.62 for Corapipo in old-growth forest at 50 m and 0.66 at 500 m, and 0.70 for Pipra mentalis in lowland old-growth forest. Results support the suggestion that geographic variation in survival rates may be common in the tropics and illustrate the need for examining survival rates separately by age and sex.
Importance of Seed Ingestion to an Avian Frugivore: An Experimental Approach to Fruit Choice Based on Seed Load
Authors: Stanley Margaret C. , Lill Alan 
Published: September 2019

AbstractFrugivorous birds may be able to reduce the cost of processing seeds by discarding seeds, selecting fruits that have a high pulp-to-seed ratio, or by choosing fruit in which seeds are packaged in a way that the frugivore's gut can void them more rapidly. A preference for fruit based on pulp-to-seed ratio or seed composition within a fruit is likely to have important implications for plants and evolution of seed size. We tested whether captive Silvereyes (Zosterops lateralis) discriminate among artificial fruit on the basis of seed presence by presenting birds with artificial fruit with or without a seed. In the first experiment, fruit were translucent so that birds could see which fruit contained a seed. In the second experiment, the visual cue was removed. When Silvereyes were presented with a choice between translucent, artificial fruit with or without a seed, they showed a strong preference for fruit that did not contain a seed. However, when the visual cue to seed presence was removed, preference for seedless fruit was still significant, but markedly reduced. We also tested seed-size preference of Silvereyes in the field in Victoria, Australia. Seeds from a fruit commonly consumed by Silvereyes, fragrant saltbush (Rhagodia parabolica), were recovered from Silvereye faecal samples and their volumes measured. Comparisons were made between seed volumes of fruit consumed by Silvereyes and those within fruit available on the plant. Silvereyes consumed significantly smaller seeds than the mean size available on saltbush plants. When Silvereyes were presented with a cereal-based diet containing artificial seeds (designed to mimic large fruit containing many small seeds), they avoided seed ingestion and were able to consume proportionally more cereal than seeds, even when on a high seed-load diet (30%). Seed dispersal by Silvereyes may be inefficient for plant species with large fruit containing many small seeds, because Silvereyes in this experiment were able to avoid ingesting seeds.
Orientation of Nocturnally Migrating Swainson's Thrush at Dawn and Dusk: Importance of Energetic Condition and Geomagnetic Cues
Authors: Sandberg Roland , Moore Frank R. , Bäckman Johan , Lõhmus Mare 
Published: September 2019

AbstractWe studied the early morning cage orientation of nocturnally migrating Swainson's Thrushes (Catharus ustulatus) during three fall migration seasons. The results were compared with earlier free-flight release tests under starry skies and were found to be consistent with continuation of migratory flights in the expected seasonally appropriate direction. Energetic condition proved decisive: fat birds chose directions in accordance with migration across the Gulf of Mexico, whereas lean birds oriented away from the coast, possibly in search of habitats suitable for refuelling. Whereas the orientation of fat Swainson's Thrushes was affected by experimental shifts of the magnetic field, the response during morning tests was larger than expected. A parallel series of orientation cage experiments performed during evening twilight showed a response to deflected magnetic fields that was close to the expected shift, which suggests a difference in integration of directional information between early morning and evening twilight activity. However, within-individual response to deflected magnetic fields was of the same magnitude during both morning and evening tests.
Density-Dependent Mass Gain by Wilson's Warblers During Stopover
Authors: Kelly Jeffrey F. , DeLay Linda S. , Finch Deborah M. 
Published: September 2019

Abstract
The need restore energetic reserves at stopover sites constrains avian migration ecology. To describe that constraint, we examined relationships among mass gained by Wilson's Warblers (Wilsonia pusilla) during stopover, abundance of Wilson's Warblers (i.e. capture rate), and arthropod abundance during autumn migration. We found that amount of mass gained by Wilson's Warblers during stopover declined as a function of their abundance. We found no relationship between mass gained by Wilson's Warblers and arthropod abundance. Abundance of Wilson's Warblers was positively associated with arthropod abundance. These patterns are consistent with the hypothesis that mass gain during stopover is density dependent. They also suggest that Wilson's Warblers respond numerically to abundance of food at that stopover site. This numerical response may override any functional response and thereby account for lack of a relationship between mass change and arthropod abundance.
Growth and Development of Prefledging Canada Geese and Lesser Snow Geese: Ecological Adaptation or Physiological Constraint?
Authors: Badzinski Shannon S. , Ankney C. Davison , Leafloor James O. , Abraham Kenneth F. 
Published: September 2019

AbstractNeonate, gosling, and adult Canada Geese (Branta canadensis interior) and Lesser Snow Geese (Chen caerulescens caerulescens) were collected to evaluate if growth rates and developmental patterns differed interspecifically and to determine if such differences were better explained by physiology of the growth process or by ecological conditions historically experienced by those two species. Patterns of growth and development of Canada and Lesser Snow goose goslings were similar to those reported for other Arctic geese, but differences in relative growth rates and developmental patterns of external structures, digestive organs, and skeletal muscles were observed between these two species. As compared to Canada Geese, body parts associated with locomotion and acquisition or processing of food generally increased at relatively faster rates and were more developed relative to adult size in Lesser Snow Geese. Relative rates of increase for carcass protein and body mass in these two species did not support a physiological constraint on growth. Rates and patterns of growth and development were better explained as adaptations to ecological factors, such as growing season and nesting or brood rearing conditions, historically experienced by these two species.
Brown-Headed Cowbird Parasitism of Ovenbirds in Suburban Forest Fragments
Authors: Hersek Marta J. , Frankel Michelle A. , Cigliano John A. , Wasserman Frederick E. 
Published: September 2019

Abstract
Forest fragmentation in North America concerns many biologists because of its effects on wildlife populations. One group that has demonstrated particular sensitivity is Neotropical migrant birds. We studied Ovenbirds (Seiurus aurocapillus) in forest fragments in a suburban landscape in eastern Massachusetts to determine effects of cowbird parasitism on Ovenbird reproductive success. Our three large (120–312 ha) and six small (10–59 ha) forests were all smaller than most of those studied by other researchers, and they were surrounded by wooded suburban lots rather than agricultural land. Twenty-nine percent of nests found were parasitized by cowbirds; that frequency is lower than other investigators have reported for small, isolated fragments. The number of Ovenbirds fledged in successful parasitized (x̄ = 2.4) and unparasitized (x̄ = 3.8) nests was similar to other studies. Cowbirds were found to remain in nests for one to two days after their Ovenbird nestmates fledged. Differences in parasitism rate between this and other Ovenbird studies may be related to landscape characteristics. Ovenbirds nesting in small fragments in relatively wooded landscapes, as was the case in this study, have higher reproductive success than do Ovenbirds nesting in similar-sized fragments within an agricultural landscape. Using Ovenbirds as a model for neotropical migrants, we suggest that small fragments in a landscape with relatively wooded connections between forested areas may allow migrants to attain higher reproductive success than similar sized forests surrounded by agricultural land.
Patterns of Egg Laying and Breeding Success in Humboldt Penguins (Spheniscus Humboldti) at Punta San Juan, Peru
Authors: Paredes Rosana , Zavalaga Carlos B. , Boness Daryl J. 
Published: September 2019

Abstract
We analyzed patterns of egg laying and breeding frequency of Humboldt Penguins (Spheniscus humboldti) between 1993 and 1997 at Punta San Juan, Peru. Egg-laying extended from mid-March to the first week of December, showing two well-defined peaks in April and August–September. The extended breeding period of these birds was the result of individuals having a second clutch. About half of the females (n =189) had two clutches per year, most of which were double broods (73%). The date of completion and outcome of reproduction, or whether a change of mates occurred from the previous year, did not affect timing of egg laying. The majority of first clutches (62%) were laid in April each year. Two-clutch breeders that started laying eggs early in April had a higher breeding success than those starting in late April, and double brooders had greater success than single brooders. Two-clutch breeders started to lay eggs earlier than single-clutch breeders. Taking into account that a penguin breeding cycle (from egg laying to fledging) lasts ∼4 months, laying eggs early in April increases the chance of rearing two successful broods per year. During three consecutive years, females tended to have two clutches instead of only one clutch and an average breeding success of 4.54 fledglings over 3 years. Having as many clutches as possible when conditions are favorable appears to be a strategy used by Humboldt Penguins to maximize their lifetime reproductive success within a productive but unpredictable environment.
Diagnosability Versus Mean Differences of Sage Sparrow Subspecies
Authors: Patten Michael A. , Unitt Philip 
Published: September 2019

AbstractA subspecies is a collection of populations within a biological species that are diagnosably distinct from other such collections of populations. That infraspecific designation has motivated a litany of spirited debates over the past half-century, from impassioned pleas for its retention to heated outcries for its abolition. We believe that the vast majority of attacks on the subspecies concept have resulted from displeasure with its improper application, not from serious flaws in the concept itself. The recognition of diagnosable subspecies allows one to address many questions not easily answered otherwise, ranging from dispersal and migration to local selection and adaptation and biogeographic affinities, yet that goal was lost for many years. Many taxonomists in the late nineteenth century and first half of the twentieth century named subspecies on the basis of average differences between populations under study, a procedure at odds with identification of diagnosable populations. To resolve that dilemma, we make explicit the established 75% rule for subspecies recognition, including formalizing the rule and developing a simple statistic to test whether diagnosability is met. The equations can be adapted readily to any level of diagnosability. We apply the concept and the statistic to a revision of the subspecies of the Sage Sparrow (Amphispiza belli). Rather than the seven named subspecies or the five that are generally considered valid, we show that only three aggregates of populations are diagnosable, and thus only three subspecies should be recognized: (1) A. b. belli in chaparral and sage scrub of coastal California, northwestern Baja California, and San Clemente Island; (2) A. b. cinerea in desert scrub of west-central Baja California; and (3) A. b. nevadensis in sagebrush and saltbush of the Great Basin and interior California. Consistent application of the 75% rule will result in fewer trinomials and a more biologically meaningful and taxonomically useful subspecies concept.
Body Condition and Parental Decisions in the Snow Petrel (Pagodroma Nivea)
Authors: Tveraa Torkild , Christensen Guttorm N. 
Published: September 2019

Abstract
In Procellariiformes, parents guard the chick for some time after it has attained homeothermy. Such a strategy may have evolved to protect the chick from predation or inclement weather, but it is costly because only one parent can forage at a time. Therefore, the decision to leave the chick seems to be a trade-off between the chick's ability to care for itself, body condition of the parent present at the nest, and ability of the bird out foraging to return to the nest before its mate's body condition has degraded. We studied chick growth and survival together with number of days Snow Petrel (Pagodroma nivea) chicks were guarded before being left alone for the first time in relation to the parents body condition and ability to return to the nest in time. Parents in good body condition were more likely to produce a chick that survived the guard stage. They also guarded their chick for a longer period (range 2–8 days, x̄ = 4.5) and finally left it alone with a higher body mass than those in poor body condition. However, whether the foraging bird was able to return to the nest in time to relieve its mate was also strongly related to number of days the chick was guarded and its body mass. The chicks' survival from when they were left alone and until day 10 posthatch was positively related both to number of days they were guarded and their body condition (body mass corrected for age).