Renal function of fresh water acclimated Glaucous-winged Gulls, Larus qlaucescens, was studied during infusion of hypotonic and hypertonic NaCl. Two experimental protocols were followed. In one, the closed urine collection system (CCS), ureteral urine was collected using catheters glued over ureteral openings of a supine, previously anesthetized gull. In the other, the open urine collection system (OCS), ureteral urine was collected through a funnel placed in the urodeum of a standing, unanesthetized bird. In both protocols, there was continuous saline infusion of hypotonic (hydration) and hypertonic (LOAD) saline at 0.286 ml⋅min⁻¹. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), ml(kg⋅min) ⁻¹, were determined by ¹⁴C-polyethylene glycol (PEG) and ³H-para-aminohippuric acid (PAH) clearances. Plasma vasotocin (PAVT, pg⋅ml⁻¹) was measured. At the end of 4 h hydration with 0.02 M NaCl, urine flow was high but matched infusion rate only in CCS birds (CCS, 0.29 ± 0.05; OCS, 0.17 ± 0.03 ml⋅min⁻¹), GFR (CCS, 5.56 ± 0.85; OCS, 5.36 ± 0.77) and ERPF (CCS, 15.80 ± 1.60; OCS, 14.35 ± 1.65) were high; urine sodium (UNa+) concentration was low (CCS, 15.0 ± 7.3; OCS, 36.4 ± 6.0 mEq⋅1⁻¹), UNa+ excretion was low (CCS, 6.38 ± 4.2; OCS, 5.19 uEq⋅min⁻¹) ; urine/plasma PEG ratio (U/PPEG) was high (CCS, 22.4 ± 4.4, OCS, 39.6 ± 8.5); free water clearance (CH₂O) was positive (CCS, 0.143 ± 0.011; OCS, 0.052 ± 0.019 ml⋅min⁻¹) , and PAVT was low (ccs,14.7 ± 7.4; OCS, 16.1 ± 2.4) in both groups. Immediately following infusion of 5 M NaCl, GFR, ERPF and urine flow increased for about 10 mins. Fifteen minutes later, the GFR of CCS gulls fell to 70% of pre-load values (P < 0.05) and in OCS gulls, GFR and ERPF fell to 64% (P < 0.01) and 61% (P < 0.05). Eighty mins after infusion of 5 M NaCl, the GFR and ERPF of CCS gulls returned to pre-LOAD levels, but remained low in OCS gulls. Twenty-five minutes after salt load, urine flow had fallen to 49% (P < 0.05) and remained low. In OCS gulls, urine flow had fallen to 13% (P < 0.001) after 185 mins. In both CCS and OCS gulls, UNa+ concentration and excretion increased significantly. Sixty minutes after salt load, UNa+ excretion returned to pre-LOAD levels but UNa+ concentration remained high in CCS (111.7 ± 57.5) and OCS (132.8 ± 12.5) gulls. U/PPEG attained 134.3 ± 26.5 in CCS and 181.2 ± 32.4 in OCS gulls. CH₂O fell significantly (P < 0.05) in CCS gulls but remained unchanged in OCS gulls. Mean PAVT increased to 122.5 ± 5.5 in CCS and 96.0 ± 12.6 in OCS gulls. In both CCS and OCS gulls, salt gland secretion was initiated but ceased 60 mins after 5M NaCl infusion, although 60% of the load was retained in the gull. / Science, Faculty of / Zoology, Department of / Graduate

Call number: LD2668 .T4 1946 L86 / Master of Science

The variable plumage characteristics of the sub-adult male cohort of the red-winged blackbird (Agelaius phoeniceus) are described. At one extreme of the plumage variation, there are a group of sub-adult males that are indistinguishable from the adult males. These birds can only be correctly aged by cloacal examination for the bursa of Fabricius in the autumn. At the other extreme, approximately 4% of the population are near perfect female-mimics. A simple scoring system based on the interspersion of dark feathers in the epaulet is presented, which permits classification of the sub-adult males into 1 of 6 plumage classes. These epaulet classes are significantly correlated with other traits of the plumage. / Age when entering the prebasic molt, and the physical condition of the sub-adult male may influence the development of the varied plumage characteristics. / The distribution of the plumage characteristics of a population of sub-adult males collected at a major blackbird roost in the province of Quebec is described for birds captured in the fall and spring. The spring plumage characteristics are more variable than the fall, a phenomenon which is not consistent with plumage wear as has been previously reported, but which may be related to a prealternate molt which the birds undergo. The prealternate molt is prevalent in some but not all of the contour feather tracts, and is restricted to females and the sub-adult male cohorts. / An age- and sex-specific spring migration of red-winged blackbirds is examined. Adult males arrive to the spring roosts first, followed by yearling males and then females. A similar pattern of dispersal to the breeding territories is described. Within the subadult male cohort, the birds with the most adult-male like plumage traits arrive at the vernal roosts first. / The characteristics of the prealternate molt and differential spring migration are discussed in relation to the pressures of sexual selection on the respective age and sex cohorts. / The adaptive significance of variable sub-adult male plumages and delayed plumage maturation in passerines is evaluated. Several competing hypotheses have been advanced to describe the phenomenon of delayed plumage maturation. These hypotheses are reviewed, and a test is proposed which unequivocally differentiates between the various alternatives. (Abstract shortened with permission of author.)

x, 30 leaves ; 28 cm Notes Typescript Thesis (M.S.)--University of Oregon, 1983 Includes vita and abstract Bibliography: leaves 28-30 Another copy on microfilm is located in Archives

No description available.

Day 14 embryos (16.5-17 day incubation period) and 1 day old chicks of Japanese quail (Coturnix japonica) were used to study the effects of different egg iodine (I) availabilities on thyroid function during development. Low (≤50 μgI/kg feed in the maternal diet) and high (1200 μgl/kg feed) I availability were compared to control levels (800 μgI/kg feed). Thyroid gland (TG) content of I, triiodothyronine (T3), and thyroxine (T4), plasma concentrations of T3 and T4, and hepatic 5’ monodeiodinase (5’-D) activity was measured, and the response of the TG to thyrotropin (TSH) stimulation [TG-cAMP content and plasma thyroid hormone (TH) concentrations]. Also, the developmental patterns of TH concentrations in the TG and plasma were determined. With increased I availability, TG-I content is elevated but thyroidal T4 and T3 and the developmental pattern of TG-TH were not different from controls. Plasma T3 and T4 and the developmental pattern of plasma TH were not altered. Indicators of the TG response to TSH stimulation were not different with increased I availability. Hepatic 5’-D activity did not differ between control and high I availability. Reduced body weight was associated with increased I availability. In general, TG weight was not altered, but a small percentage of the high I birds exhibited TG hypertrophy and altered TG function. With low I availability, TG-I content was reduced. Although thyroidal T4 content was reduced on embryonic day 14 and thereafter, TG-T3 was maintained throughout development. The magnitude of the TG response to TSH stimulation was not altered with reduced I availability. Hepatic 5’-D activity, plasma TH concentrations and the developmental patterns of plasma TH were not different between control and low I availability. Reduced I availability did not affect body or TG weight. Developing Japanese quail exhibit excellent ability to adjust thyroid function over a wide range of I availabilities. Regulation appears to occur at TH synthesis which allows most aspects of thyroid dynamics to remain unchanged in the maintenance of circulating TH concentrations. / Master of Science

No description available.

Recent evidence suggests that avian facultative hypothermic responses are more common than previously thought. Traditionally, several categories of avian hypothermic responses have been recognized, and are frequently differentiated on the basis of minimum body temperature (T[b]) The available data suggest that the capacity for shallow hypothermia (rest-phase hypothermia) occurs throughout the avian phylogeny, but that the capacity for pronounced hypothermia (torpor) is restricted to certain taxa. However, there are currently too few data to test hypotheses concerning the evolution of avian hypothermic responses. Facultative hypothermia occurs over most of the avian body mass (M[b]) range, but is most common in small species. Minimum body temperature during hypothermia (T[min]) is continuously distributed from 4.3 °C to ca. 38°C. The continuous T[min] distribution, as well as recent evidence that the T[b] ranges of different avian physiological states may overlap, question the biological reality of specific T[b] limits. Pattens of thermoregulation during avian hypothermic responses are relatively variable, and do not necessarily follow the entry-maintenance-arousal patterns that characterize mammalian responses. Avian hypothermic responses are determined by a suite of ecological and physiological determinants. I investigated normothermic thermoregulation and hypothermic responses to restricted food in the speckled mousebird Colius striatus in the context of the distinction between normothermia, rest-phase hypothermia, and torpor. The lowest T[b] recorded in a bird which was able to arouse spontaneously was 18.2°C. However, I was unable to clearly discern between normothermic, hypothermic and torpor T[b] ranges. Furthermore, hypothermic responses did not accord with the patterns typically observed in birds and mammals. Metabolic suppression normally associated with entry into torpor and the defence of a torpor T[b] setpoint was largely absent. Laboratory data for C. striatus, as well as published data for Colius colius suggest that clustering behavior plays an important thermoregulatory role in mousebirds. Hence, I investigated thermoregulation under semi-natural conditions in C. striatus. In particular, I was interested in the interaction between clustering behavior and hypothermic responses during energy stress (restricted feeding). In contrast to clustering birds, rest-phase thermoregulation in single birds was characterised by linear decreases in T[b] and the birds did not appear to defend a specific T[b] setpoint. During restricted feeding, both clustering and single birds exhibited significant decreases in rest-phase T[b]. The extent of these facultative hypothermic responses was greater in single birds than in clustering birds, supporting the prediction that clustering behavior moderates the use of facultative hypothermia. I also tested the prediction that in free-ranging C. colius, the use of heterothermy should be rare, even at the coldest time of the year. I recorded mid-winter rest-phase body temperatures (T[b]) in a flock of free-ranging C. colius in an arid habitat in the Karoo, South Africa. The mousebirds' rest-phase T[b] was fairly labile, but was maintained above 33°C, despite T[a]s as low as -3.4 °C. The mousebirds showed no evidence of torpor under natural conditions; a facultative hypothermic response, during which T[b] was reduced to 29 - 33°C, was only observed on one occasion. The observed patterns of thermoregulation supported my predictions, and suggest that thermoregulation in clustering C. colius in the wild is significantly different to that of single birds under laboratory conditions. My results also suggest that the pronounced capacity for heterothermy usually associated with mousebirds is not necessarily representative of their patterns of thermoregulation under natural conditions. The capacity for avian torpor appears to be dependent on phylogeny. To investigate phylogenetic constraints on the capacity for torpor, I measured metabolic responses to food deprivation in a small, arid-zone passerine, the red-headed finch (Amadina erythrocephala). I observed significant reductions in rest-phase energy expenditure and body temperature (T[b]) in response to restricted feeding. The maximum extent of T[b] suppression (ca. 5°C) and energy savings (ca. 10%) were consistent with those reported for a number of other passerines. The lowest T[b] I observed in a bird able to arouse spontaneously was 34.8°C. My data support the hypothesis that the capacity for heterothermy in passerines is phylogenetically constrained, and that the majority cannot employ torpor in response to energetic stress. Selection for the capacity for torpor is presumably similar to the selection pressures acting on other avian energetic traits, such as basal metabolic rate (BMR). I tested the generality of a recent model linking the slow-fast mammalian metabolic continuum to global patterns of climatic predictability using BMR data for 219 non-migratory bird species. Avian BMR varied significantly between zoogeographical zones, with Afrotropical, Indomalayan and Australasian species generally exhibiting lower BMR than Holarctic species. In addition, the magnitude of differences between arid and mesic species varied between zones. In the Nearctic, these differences were pronounced, whereas no significant differences were evident for Afrotropical or Australasian species. A slow-fast metabolic continuum similar to that described in mammals appears to exist for birds, with higher BMR associated with predictable, seasonal environments and lower BMR with less predictable environments, in particular those affected by the El Niño Southern Oscillation. I constructed a generalised, conceptual model which attempts to predict the occurrence of torpor using phylogeny, M[b] constraints, a trade-off between energetic benefits and potential ecological costs, and specific ecological factors. A recent hypothesis suggests that endotherm heterothermy is monophyletic, and predicts that torpor should be more widespread in phylogenetically older taxa. Once phylogeny is considered, the most important determinant of avian torpor is M[b]. I used an existing model of endotherm torpor to predict the relationship between M[b] and minimum T[b] during torpor. The available data show that the lower limit of torpor T[b] is determined by the M[b]-dependent costs of rewarming following a torpor bout. Finally, I constructed a model based on the assumption that torpor is adaptive if the energetic benefits exceed the potential ecological costs. The model predicted that torpor should be more prevalent in species near the extremes of the avian metabolic continuum. The available data provide tentative support for this prediction. In addition to generalised factors such as phylogeny and M[b], specific aspects of a particular species' ecology need to be considered when predicting the occurrence of avian torpor. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2001.

Achievement of endothernic capacity is vital for independence from ambient temperature changes, sustained activity, optimal biochemical reactions and optimization of parental care. During early avian development, the core tenets of transition from ectothermy to endothermy are development of metabolic capacity (oxygen consumption, mitochondrial bioenergetics), enhanced cardiovascular function (heart rate and cardiac output), pulmonary ventilation and thermogenic capacity. Thyroid hormones, particularly T3, are key metabolic regulators of basal metabolism, thermogenesis, pulmonary ventilation and mitochondrial respiration. Thyroid hormone fluctuation patterns during both precocial and altricial avian endothermic transition suggest a prominent role in maturation of endothermy, cardiovascular, respiratory and skeletal muscle physiology. This body of work explores effects of T3 manipulations in two avian species: the precocial Pekin duck and the altricial Red-winged Blackbird. Increased plasma T3 during late incubation resulted in increased cardiac mass, elevated resting and intrinsic heart rate, intrinsic mean arterial pressure, increased cholinergic tone and blunted alpha-adrenergic tone in the precocial Pekin duck. In both Pekin duck and Red-winged blackbird, plasma T3 levels correlated with changes in the trajectory of endothermic ontogeny, systemic oxygen consumption, thermogenesis, maturation of pulmonary ventilatory function, altered growth and effects on skeletal and cardiac mitochondrial bioenergetics. These observations support the role of thyroid hormones as metabolic and developmental regulators at the time of attainment of endothermy during the perinatal period in precocial and altricial avian species. Insights into the role of thyroid hormone as a metabolic and development regulator at the time of avian endothermic attainment provide a more thorough understanding of metabolic and physical transitions a hatchling bird must undergo to reach the adult endothermic phenotype. Such insights also deepen understanding of the complex role thyroid hormones play in homeostasis and offer implications about the evolutionary history of endothermic capacity.

Deserticolous birds inhabit an environment characterised by high ambient temperatures and low rainfall that has low primary productivity. The combination of these factors may lead to the evolution of adaptations that minimise food and water requirements. One physiological adaptation that has been found in many deserticolous birds is the reduction of basal metabolic rate (BMR). I measured metabolic rate in the laboratory using four species of African lovebirds (Agapornis) , and four species of Australian grass parakeets (one Neopsephotus and three Neophema), all similar in body mass. Tests for differences between groups were carried out using both conventional and phylogenetically independent methods. The BMRs of the lovebird and grass parakeet species were not statistically correlated with habitat type. These results confirm the findings of previous studies on the effect of desert conditions on the BMR of parrots. I also found no significant differences in BMR between the species assemblages from different continents. The lack of significant differences in BMR between deserticolous and nondeserticolous parrots supports the idea that birds are "ex-adapted" to living in desert environments. I suggest that the results may have been affected by phenotypic plasticity in BMR, as recent evidence has shown that the scaling exponent of BMR differs between captive-raised and wild-caught birds. To elucidate the effect of origin (captive-raised vs. wild-caught) on the BMR of birds used in this study a large scale analysis of bird BMR data was undertaken. BMR and body mass data for 242 species of birds were obtained from the literature, this study, and unpublished data from various sources. A phylogeny was constructed using molecular and morphological phylogenies from the literature, and analysed using conventional and phylogenetically independent methods. The conventional analysis found significant differences in the scaling exponents of BMR of captive-raised and wild-caught birds. However the phylogenetically independent method showed non-significant differences between these two groups. Conventional analysis of differences between parrots and all other birds yielded significant differences between these two groups, with parrots having significantly higher BMRs than other birds. Again the phylogenetically independent analysis found non-significant differences between these VII two groups. A test of homogeneity of variance between these two groups found significant differences between the variances ofthe two groups, probably due to disparity in sample size and range of body sizes. The conventional and phylogenetically independent tests for differences between captive-raised and wild-caught parrots yielded non-significant results, suggesting that the parrots are not subject to the phenotypic adjustments postulated for all other birds. The lack of significant differences between captive-raised and wild-caught parrots suggests that the analyses of differing habitat type for African and Australian parrots is indeed valid. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.