Seasonal Thermoregulation In The Dark Eyed Junco Passeriformes Junco Hyemalis
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Seasonal Thermoregulation In The Dark Eyed Junco Passeriformes Junco Hyemalis
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Author : David Leslie Swanson
language : en
Publisher:
Release Date : 1990
Seasonal Thermoregulation In The Dark Eyed Junco Passeriformes Junco Hyemalis written by David Leslie Swanson and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1990 with Body temperature categories.
Winters in north-temperate climates impose high thermogenic demands upon small birds which are met by seasonal acclimatization. This thesis investigates the extent and mechanisms of seasonal acclimatization in darkeyed juncos (Junco hyemalis) inhabiting western Oregon. Although insulation is significantly increased in winter, acclimatization is primarily metabolic. Increased metabolism is required to offset heat loss even at moderate temperatures at both seasons. At average daily temperatures, thermoregulation in January requires 1.8 times the energy expended for thermoregulation in July and August. Standard metabolic rate (SMR) is significantly elevated in winter (3.45 mL02[gXhr]−1) compared to summer (3.16 mL02[gXhr]−1), suggesting elevated metabolic capacities. Furthermore, winter birds, but not summer birds, were capable of modifying thermal conductance at low temperatures, allowing additional heat conservation. Helium/oxygen cold stress demonstrated that cold tolerance was improved in winter juncos relative to summer birds. Maximal thermogenic capacity also increased significantly in winter birds (7.39 mLO2 /min to 5.78 m102/min). These values exceed SMR by 7.2 times in winter and 6.6 times in summer. Oxygen dissociation curves were generated on whole blood by saponin/potassium ferricyanide dissociation and were similar to those for other passerines. The curves did not vary significantly between summer and winter (P50 = 54 torr). Hematocrit and oxygen carrying capacity were significantly increased in winter. Apparently increased oxygen demands in winter juncos are met, in part, by increased oxygen carrying capacity, but not by decreased oxygen affinity. Plasma and tissue metabolites were assayed after differing levels of cold stress to analyze seasonal variation in carbohydrate and lipid metabolism. Pectoralis muscle glycogen was significantly greater after severe cold stress in winter, although thermoneutral levels did not vary significantly. Furthermore, plasma levels of free fatty acids were significantly increased and plasma glucose was significantly decreased under severe cold. These data suggest reduced reliance upon carbohydrate for shivering thermogenesis in winter juncos and subsequent preservation of muscle glycogen stores. This may contribute to enhanced shivering endurance and cold tolerance in winter birds.
Effects Of Environmental Variation At Multiple Scales On The Dark Eyed Junco Junco Hyemalis In California
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Author : Kathleen LaBarbera
language : en
Publisher:
Release Date : 2016
Effects Of Environmental Variation At Multiple Scales On The Dark Eyed Junco Junco Hyemalis In California written by Kathleen LaBarbera and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
The selective pressures acting on phenotypes are complex and can vary over space and time. To examine the effects of selection due to environmental conditions on avian bill morphology, we explored spatial and temporal variation in bill morphology in a common generalist songbird, the Dark-eyed Junco (Junco hyemalis). We measured bill length, width, and depth, and calculated surface area, for >800 museum specimens collected in the state of California from 1905-1980. We then examined which environmental variables (precipitation, temperature, and habitat type) at which temporal scales (seasonal, annual, hemi-decadal, and decadal) could explain variation in each measure of bill morphology. Although we predicted relationships consistent with selection on the bill for foraging utility and optimal thermoregulation, the patterns we found were more complex. The effects of the environmental factors examined varied with season and with the specific bill traits. Measures of habitat type were more strongly associated with bill morphology than were individual climate variables, and temperature was a more important predictor of bill morphology than precipitation. Bill surface area displayed stronger effects of environmental conditions than did linear measures of bill morphology. Of the climate variables identified as important in our analyses, support was strongest for the measure of decadal temperature variability. The strong relationship between vegetative community and bill surface area in our models, the support for longer-term temperature variables, and the support for the importance of temperature variability suggests that in complex natural systems, large-scale context--ecology and climate--plays a strong role that is not seen by looking at its component parts alone. Different environmental conditions produce different selective pressures. We explored patterns of life history variation along an elevation gradient to identify the factors contributing to this variation. We monitored breeding Dark-eyed Juncos in the Sierra Nevada mountains of California at sites from 1960 to 2660 m above sea level and compared breeding season length, temporal patterns of peak breeding activity, clutch size, brood size, nestling quality, and nest mortality among elevations. We also compared maximum and minimum daily temperature, daily snow depth, and monthly precipitation across the elevations to determine whether these abiotic factors could explain life history variation. We found small differences in breeding season length and in the pattern of reproductive timing among elevations. While breeding season at the intermediate elevation was intermediate in length, the pattern of peak breeding activity was not intermediate between the patterns observed at low and high elevations. The life history differences across elevations could not be explained solely by abiotic factors, but may be related to the effects of those factors on the birds' prey base or nesting sites, potentially exacerbated at lower elevations by the ongoing drought. We found no differences among elevations in clutch size, brood size, or nestling quality. Higher elevations had greater nest mortality, possibly due to severe weather. A computer simulation constructed to mimic the field system suggests that these mortality differences, in combination with the differences in breeding season length, contribute to substantial differences among elevations in reproductive success which may be difficult to observe in a field setting. We then investigated whether variation in climatic conditions, breeding season length, and number of offspring produced per season in populations of junco breeding at different elevations led to variation in breeding synchrony, in extra-pair paternity, or in the use of a sexually-selected male signal, the amount of white in the tail. We also tested for genetic structure among the populations. Using 12 variable microsatellite loci, we found differences in extra-pair paternity rates among our populations, with a low extra-pair paternity rate (20% of nests) at high elevations, a high rate (57%) at middle elevations, and an intermediate rate (38%) at low elevations. We found no differences among elevations in mean values of tail white or tail white asymmetry, and no differences in a measure of the honesty of the signal (the strength of the correlation between tail white and either of two indices of male quality). Despite differences in the temporal patterns of breeding activity as well as in the length of the breeding season, we found no differences in breeding synchrony among elevations, and no association between the presence of extra-pair paternity and a brood's breeding synchrony. We detected no genetic differentiation among populations, indicating that consistent gene flow occurs between the populations. Persistent gene flow may explain the lack of differentiation in the tail white signal despite substantial differences in the potential strength of sexual selection among elevations.
Effects Of Seasonal Changes In The Dark Eyed Junco Junco Hyemalis
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Author : Sara Elizabeth Schrock
language : en
Publisher:
Release Date : 2007
Effects Of Seasonal Changes In The Dark Eyed Junco Junco Hyemalis written by Sara Elizabeth Schrock and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
Wildlife Review
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Author :
language : en
Publisher:
Release Date : 1991
Wildlife Review written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1991 with Natural history categories.
The Habitat Preference Of The Dark Eyed Junco Junco Hyemalis
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Author : Edgar Parsons Roberts
language : en
Publisher:
Release Date : 1979
The Habitat Preference Of The Dark Eyed Junco Junco Hyemalis written by Edgar Parsons Roberts and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1979 with Habitat selection categories.
Sturkie S Avian Physiology
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Author : G. Causey Whittow
language : en
Publisher: Elsevier
Release Date : 1999-10-14
Sturkie S Avian Physiology written by G. Causey Whittow and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999-10-14 with Science categories.
Sturkie's Avian Physiology is the classic comprehensive single volume on the physiology of domestic as well as wild birds. The Fifth Edition is thoroughly revised and updated, and includes new chapters on the physiology of incubation and growth. Chapters on the nervous system and sensory organs have been greatly expanded due to the many recent advances in the field. The text also covers the physiology of flight, reproduction in both male and female birds, and the immunophysiology of birds. The Fifth Edition, like the earlier editions, is a must for anyone interested in comparative physiology, poultry science, veterinary medicine, and related fields. This volume establishes the standard for those who need the latest and best information on the physiology of birds. Thoroughly updated and revised Coverage of both domestic and wild birds New larger format Only comprehensive, single volume devoted to birds
Current Ornithology
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Author : Val Nolan Jr.
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-06-29
Current Ornithology written by Val Nolan Jr. and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-06-29 with Science categories.
Current Ornithology publishes authoritative, up-to-date, scholarly reviews of topics selected from the full range of current research in avian biology. Topics cover the spectrum from the molecular level of organization to population biology and community ecology. The series seeks especially to review (1) fields in which an abundant recent literature will benefit from synthesis and organization, or (2) newly emerging fields that are gaining recognition as the result of recent discoveries or shifts in perspective, or (3) fields in which students of vertebrates may benefit from comparisons of birds with other classes. All chapters are invited, and authors are chosen for their leadership in the subjects under review.
Avian Energetics And Nutritional Ecology
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Author : C. Carey
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Avian Energetics And Nutritional Ecology written by C. Carey and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.
A symposium held in 1973 chaired and organized by William R. Dawson was the first major attempt to summarize and synthesize the existing information in the then emerging field of avian energetics. The symposium featured papers by James R. King, William A. Calder III, Vance A. Tucker, and Robert E. Ricklefs and com mentaries by George A. Bartholomew, S. Charles Kendeigh, and Eugene P. Odum. The proceedings of the symposium, Avian Energetics (Paynter 1974), played a critical role in stimulating interest and research in the field of avian energetics. Some twenty-odd years later, we are making another attempt to summarize the information in the field of avian energetics. Some obvious differences exist be tween its predecessor and this volume. Numerous improvements in methodology, such as the use of doubly labeled water to estimate metabolism in free-living birds, now allow researchers to ask questions that could not be addressed previ ously. Second, consideration of nutrition is now inseparable from that of energet ics. This merger is necessary not only because food intake is the source of both en ergy and nutrients but also because one or more nutrients, rather than energy, can be limiting for a given species in a particular instance. Finally, the study of ener getics and nutritional ecology, particularly in birds and mammals, has grown so dramatically that a single volume can now only partially cover the range of possi ble topics and can catalogue only a sampling of all the studies on the subject.
Physiological Zoology
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Author :
language : en
Publisher:
Release Date : 1996-07
Physiological Zoology written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996-07 with Physiology categories.
The Journal Of Experimental Biology
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Author :
language : en
Publisher:
Release Date : 2007
The Journal Of Experimental Biology written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Biology categories.