Velocity and pressure fluctuations were measured in a wind tunnel in the plane of symmetry in front of a wing-body junction at an approach free-stream velocity U_ref=28.3 m/s and momentum thickness Reynolds number Re_θ=6900. The cylindrical wing shape was a 3:2 elliptic nose attached to a NACA 0020 tail at maximum thickness. A two component laser Doppler anemometer was used to make the velocity measurements. Pressure measurements were made at two locations upstream of the wing by a pair of Sennheiser microphones. A relationship between the velocity and pressure was determined to reveal the bimodal structure of the flow field. Histograms and power spectra of both quantities are presented along with cross-spectra and cross-correlations. The velocity power spectra revealed spectral slopes of -1 through out the entire flow field. Velocity and pressure autospectra show the bimodal region to be dominated by low frequency fluctuations centered at ft/U_ref=5x10⁻², where f is the average frequency and t is the maximum wing thickness. Coherence was found between velocity fluctuations and pressure fluctuations in three frequency bands, each associated with a particular region of the wing-body junction flow field. Low frequency coherence between the velocity and pressure was found in the vicinity of the junction vortex where large scale unsteady bimodal structures are formed. High frequency coherence dominates closer to the juncture of the wing and body. Conditionally-averaged velocity vectors were used to help identify the flow structure in the juncture. These vectors were used along with the other data to propose a model consisting of a single vortex rolling up and moving downstream. As the vortex moves downstream, it wraps around the wing which causes it to stretch and eventually dissipate. Preceding the vortex roll up, an intake of fluid down the wing occurs which is believed to be the cause of the bimodal unsteadiness. / Master of Science

No description available.

The journey of structural studies on lectins, starting with ConA in the 70s, has crossed many milestones. Lectins, multivalent carbohydrate-binding proteins of non-immune origin, specifically bind diverse sugar structures. They have received considerable attention in recent times on account of the realization of the importance of protein-sugar interactions, especially at the cell surface, in biological recognition. They occur in plants, animals, fungi, bacteria and viruses. Plant lectins constitute about 40% of the lectins of known structure. They can be classified into five structural groups, each characterized by a specific fold. Among them, legume lectins constitute the most extensively investigated group. Basic Winged bean lectin (WBAI) is a glycosylated, homodimeric, legume lectin with Mr 58000. The structure of WBAI complexed with methyl-a-galactose, determined earlier in this laboratory, provided information about the oligomeric state and the carbohydrate specificity of the lectin in terms of lectin-monosaccharide interactions. The present work was initiated to understand the carbohydrate specificity of the lectin, especially at the oligosaccharide level, with special reference to its blood group specificity. The hanging drop method was used for crystallizing WBAI and its complexes. Intensity data were collected on Mar Research imaging plates mounted on Rigaku RU-200 or ULTRAX-18 X-ray generators. The data were processed using DENZO and SCALEPACK of HKL suite of programs. The structure factors from the processed data were calculated using TRUNCATE of CCP4 suite of programs. The molecular replacement program AMoRe was used for structure solution. Structure refinement was carried out using the CNS software package. Model building was done using the molecular graphics program O. INSIGHT II, ALIGN, CONTACT and PROCHECK of CCP4 were used for the analysis and validation of the refined structures. WBAI exhibits differential affinity for different monosaccharide derivatives of galactose. In order to elucidate the structural basis for this differential affinity, the crystal structures of the complexes of basic winged bean lectin with galactose, 2-methoxygalactose, N-acetylgalactosamine and methyl-a-N-acetylgalactosamine have been determined. Lectin-sugar interactions involve four hydrogen bonds and a stacking interaction in all of them. In addition, a N-H O hydrogen bond involving the hydroxyl group substituted at C2 exists in the galactose and 2-methoxygalactose complexes. The additional hydrophobic interaction, involving the methyl group, in the latter leads to the higher affinity of the methyl derivative. In the lectin - N- acetylgalactosamine complex the N-H O hydrogen bond is lost, but a compensatory hydrogen bond involving the oxygen atom of the acetamido group is formed. In addition, the CH3 moiety of the acetamido group is involved in hydrophobic interactions. Consequently, the 2-methyl and the acetamido derivatives of galactose have nearly the same affinity for the lectin. The methyl group, a-linked to the galactose, takes part in additional hydrophobic interactions. Therefore, methyl-a- N-acetylgalactosamine has higher affinity than N-acetylgalactosamine to the lectin. The structures of basic winged bean lectin-sugar complexes provide a framework for examining the relative affinity of galactose and galactosamine for the lectins that bind to them. The complexes also lead to a structural explanation for the blood group specificity of basic winged bean lectin, in terms of its monosaccharide specificity. The Tn-determinant (GalNAc-a-O-Ser/Thr) is a human specific tumor associated carbohydrate antigen. Having epithelial origin, it is expressed in many carcinogenic tumors including breast, prostate, lung and pancreatic cancers. The crystal structure of WBAI in complex with GalNAc-a-O-Ser (Tn-antigen) has been elucidated, in view of its relevance to diagnosis and prognosis of various human cancers. The Gal moiety occupies the primary binding site and makes interactions similar to those found in other Gal/GalNAc specific legume lectins. The nitrogen and oxygen atoms of the acetamido group of the sugar make two hydrogen bonds with the protein atoms whereas its methyl group is stabilized by hydrophobic interactions. A water bridge formed between the terminal oxygen atoms of the serine residue of the Tn-antigen and the side chain oxygen atom of Asn128 of the lectin increase the affinity of the lectin for Tn-antigen compared to that for GalNAc. A comparison with the available structures reveals that while the interactions of the glyconic part of the antigen are conserved, the mode of stabilization of the serine residue differs and depends on the nature of the protein residues in its vicinity. The structure provides a qualitative explanation for the thermodynamic parameters of the formation of the complex of the lectin with Tn-antigen. Modelling studies indicate the possibility of an additional hydrogen bond with the lectin when the antigen is part of a glycoprotein. WBAI binds A-blood group substance with higher affinity and B-blood group substance with lesser affinity. It does not bind the O substance. The crystal structures of the lectin, complexed with A -reactive and B - reactive di and tri saccharides, have been determined. In addition, the complexes of the lectin with fucosylated A- and B-trisaccharides and with a variant of the A-trisaccharide have been modelled. These structures and models provide valuable insights into the structural basis of blood group specificities. All the four carbohydrate binding loops of the lectin contribute to the primary combining site while the loop of variable length contributes to the secondary binding site. In a significant advance to the current understanding, the interactions at the secondary binding site also contribute substantially, albeit in a subtle manner, to determine the blood group specificity. Compared to the interactions of the B- trisaccharide with the lectin, the third sugar residue of the A -reactive trisaccharide forms an additional hydrogen bond with a lysine residue in the variable loop. In the former, the formation of such a hydrogen bond is prevented by a shift in the orientation of the third sugar resulting from an internal hydrogen bond in it. The formation of this bond is also facilitated by an interaction dependent change in the rotamer conformation of the lysyl residue of the variable loop. Thus, the difference in the interactions at the secondary site is generated by coordinated movements in the ligand as well as the protein. A comparison of the crystal structure and the model of the complex involving the variant of the A-trisaccharide results in the delineation of the relative contributions of the interactions at the primary and the secondary sites in determining blood group specificity. At the disaccharide level, WBAI exhibits higher affinity for á1-3 linked Gal/GalNAc containing oligosaccharides, compared to that of other á linked oligosaccharides. With an objective of understanding the preferential binding of WBAI for á 1-3 linked Gal/GalNAc containing oligosaccharides, crystal structure of the complexes of the lectin with Galá1-4Gal, Galá1-4GalâEt and Galá1-6Gal have been determined. The reducing sugar of the disaccharides with linkages other than á1-3 binds to the lectin through a water bridge whereas the same sugar moiety with á 1-3 linkage makes direct interactions with the loop L4 of the protein. The modelling study on the complex of the lectin with Galá1-2Gal further upholds this observation. Different structures involving WBAI, reported earlier and presented here, were used to investigate the plasticity of the lectin. The front curved â-sheet, which nestles the metal binding region and on which the carbohydrate binding loops are perched, is relatively rigid. On the contrary, the flat back â-sheet, involved in the quaternary association in legume lectins, is flexible. This flexibility is probably necessary to account for the variation in quaternary structure. With the results presented in this thesis, 14 crystal structures of WBAI, in the free form and in complex with different sugars, have been reported, all from this laboratory. It is now, perhaps, appropriate to examine the new information and insights gained from these investigations, on the structure and function of the lectin. Earlier X-ray studies of WBAI contributed substantially in establishing that legume lectins are a family of proteins in which small alterations in essentially the same tertiary structure lead to large alterations in quaternary association. Structural studies on WBAI, particularly those reported here, also contributed to the elucidation of the nuances of carbohydrate recognition by lectins. A comparative study of the available structures also revealed the flexible and rigid regions of the protein. The study of the influence of covalently linked sugars on the structure of Erythrina corallodendron lectin (ECorL), a homolog of WBAI, is the content of appendix of the thesis. The three-dimensional structure of the recombinant form of Erythrina Corallodendron lectin(rECorL) complexed with lactose, has been elucidated by X-ray crystallography. Comparison of this non-glycosylated structure with that of the native glycosylated lectin reveals that the tertiary and quaternary structures are identical in the two forms, with local changes observed at one of the glycosylation sites(Asn17). These changes take place in such a way that hydrogen bonds with the neighbouring protein molecules in rECorL compensate those made by the glycan with the protein in ECorl. contrary to an earlier report, this study demonstrates that the glycan attached to the lectin does not influence the oligomeric state of the lectin. Identical interactions between the lectin and the non-covalently bound lactose in the two forms indicate, in line with earlier reports, that glycosylation does not affect the carbohydrate specificity of the lectin. The present study, the first of its kind involving a glycosylated protein with a well defined glycan and the corresponding deglycosylated form, provides insights into the structural aspects of protein glycosylation.

Many organisms use both vegetation structure and social cues in selecting habitats. Many species of songbirds use the presence of breeding conspecifics as a social cue and sign of habitat quality, and can be induced to settle in unoccupied habitats by artificially broadcasting breeding song, a process referred to as “conspecific attraction”. In our study, we tested response to conspecific attraction a low-density population of the threatened Golden-winged Warbler (Vermivora chrysoptera) in Highland County, VA. Response to broadcast song was observed, with a modest increase in mean male abundance at survey points within 250 meters of treatments, and mean abundance decreasing outside of this range throughout the study area. Recruitment to conspecific playback was lower in our study than observed in previous research on high-density systems. Our results suggest more research is needed of the effectiveness of conspecific attraction in low density species and that its use should be tailored to the spatial and demographic conditions of the managed population.

The biology of the red-winged blackbird (Agelaius phoeniceus) was studied in relation to variations in agricultural landscapes of southwestern Quebec, eastern Ontario, and southwestern Ontario by examining the relationships between corn (Zea mays) production and population size, distribution of territorial males, and morphology. Dietary studies showed consistent use of corn during their 6-9 month residency in these regions, and during winter months. / A positive correlation was found between independent estimates of the density of males and counts of red-wings obtained from the North American breeding bird survey (BBS). Density of males was a useful indicator of the number of red-wings in an area, whereas the BBS was a useful indicator of change in regional population level. / Historical increases in populations of red-wings in these regions were correlated with increases in waste grain (corn) following harvest. Greater rates of population increase in Quebec (compared with Ontario) corresponded to higher rates of increase in waste corn abundance and landscape heterogeneity. In Quebec, cultivation (mainly corn) was the most important habitat influencing density of males. Wetland and hay field abundance were also important. Heterogeneous landscapes incorporating crops, wetlands and hay fields attracted the most male red-wings regardless of population level, and breeding males preferred wetlands and hay fields for territory establishment. Fields were used in proportion to abundance, whereas forest, crops and areas of human occupation were avoided. At high population density, proportionately more males settled in areas of human occupation and in fields; these habitats were less suitable than wetlands or hay fields. Packing of males into a preferred hay field habitat occurred. / Overwinter mortality did not favor small body size in male red-wings but evidence of stabilizing selection on female body size was found. Sexual dimorphism was slightly more pronounced in spring than in fall. Historical changes in the body size of red-wings were not clearly related to increasing abundance of food (corn). If population size tracks increases in food abundance, then inter-male competition for breeding space may intensity; thus, large size may be limited by energy contraints imposed on males by sexual selection pressure regardless of food availability.

Obligate brood parasites rely solely on other species, the hosts, to incubate their eggs and raise their offspring, which often reduces the host’s reproductive output. This reproductive cost has led to the evolution of anti-parasite adaptations among hosts, which in turn, has led to better trickery by parasites, a process termed an evolutionary arms race. The objective of this thesis was to investigate host-parasite coevolutionary arms races to address questions of host-use diversity. Host diversity varies dramatically among brood-parasitic species, but reasons for variations in host-use among brood parasites are not well understood. In Chapter 2, I address questions on host diversity specifically, whereas I address questions about coevolutionary interaction between hosts and parasites in Chapters 3, 4 and 5 using two host-parasite systems, one in New Zealand and one in North America. Chapter 2 investigates if host diversity is constrained by aggressive nest defence behaviour. I compared the nest defence behaviour of the exclusive host of the shining cuckoo Chrysococcyx lucidus lucidus on the main islands of New Zealand, the grey warbler Gerygone igata, to two other potentially suitable hosts that are not currently parasitised, the fantail Rhipidura fuliginosa and the silvereye Zosterops lateralis. The results suggest that grey warblers are as aggressive as fantails and silvereyes towards shining cuckoos at the nest and thus, host specialisation in shining cuckoos in New Zealand, at least, does not appear to be the result of nest-defence constraints imposed by potential but unused host species. Chapter 3 investigates if red-winged blackbirds Agelaius phoeniceus, a species that typically accepts the eggs of parasites, recognises, as indicated by changes in incubation behaviour, when they have been parasitised by brown-headed cowbirds Molothrus ater. Recognition without rejection suggests that rejection may be context-dependent but the results suggest that red-winged blackbirds do not recognise when their nests have been parasitised by brown-headed cowbirds, at least at the egg stage. This study was the first to investigate if hosts that almost invariably accept the eggs of parasites recognise when they have been parasitised. Chapter 4 investigated the possibility of coevolutionary arms races occurring through olfactory channels in contrast to earlier work that focussed only on visual and auditory cues. Recent research has revealed that olfactory abilities in birds are more common than previously thought. Uropygial gland secretions are posited to be a key source of avian body odour and its composition has been found to vary among species and individuals as well as between the sexes. I compared gas-chromatography (GC-FID) traces of shining cuckoo preen wax to the GC-FID traces of the grey warbler, the only host of the shining cuckoo in mainland New Zealand, as well as the preen wax of seven other species for evidence of mimicry. Preliminary results suggest there is evidence for mimicry and the potential for odour-based nestling discrimination in grey warblers. Further tests recording the response of grey warblers to odour-manipulated nestlings are necessary. Finally, in Chapter 5, I investigated the response of the song thrush Turdus philomelos, a species that rejects the eggs of the common cuckoo Cuculus canorus and conspecifics at intermediate and low frequencies, respectively, to nest-odour manipulations using the preen wax of conspecifics and heterospecifics. The results suggest song thrush do not use odour to assess the risk of parasitism at least as indicated in terms of changes in incubation behaviour. Investigations of the role of olfaction in avian brood parasite systems can provide a better understanding of brood-parasite coevolution. Only by considering all channels of communication can we be sure to completely understand the coevolutionary dynamics between brood parasites and their hosts.

Over the past several decades, there has been growing concern among the public and scientific community regarding adverse health effects resulting from exposure to natural and synthetic compounds that act as endocrine disrupters. The structural similarity of many of these compounds to natural hormones and receptors, as well as their ubiquity in the environment, can result in the potential for interference with the endocrine system of wildlife and humans. Much of the research examining the adverse effects of wildlife exposure to endocrine disrupting chemicals (EDCs) has focused on effects on reproduction or short-term changes in hormone physiology. However, organisms exposed to low levels of EDCs at early life stages could also be susceptible to developmental effects, including neurological and other physiological changes affecting later life stages. In birds, migration can be an important component of the annual life cycle and it can be vulnerable to disruption given that it is under endogenous hormonal and neurological control. Previous studies have shown that developmental exposure of birds to thyroid hormone disruptors, such as polychlorinated biphenyls (PCBs), have resulted in reduced hatching success, lower growth rates, teratogenicity, impaired development, and immunotoxicity. In this thesis, I aimed to supplement what is currently known regarding the effects of developmental exposure to low levels of a mixture of endocrine disrupting chemicals in songbirds, as well as further investigate the latent consequences of such an exposure on migratory life stages. I initially investigated the potential physiological and developmental effects of early exposure to Aroclor 1254, a PCB mixture, in two passerine songbird species: European starlings (Sturnus vulgaris) and red-winged blackbirds (Agelaius phoeniceus) during the critical nestling period. In 2011, European starlings and red-winged blackbirds were orally administered Aroclor 1254 over the period of nestling development, which was repeated in 2012 with only European starlings. For both years, morphological parameters (body mass, tarsus, wing-chord and bill-lengths) were measured daily and plasma thyroid hormones were measured. Additional measurements of wing chord and tarsus length fluctuating asymmetry (FA) were taken in the second year, to further assess contaminant-induced alterations in developmental stability. I found that treatment with environmentally-relevant levels of Aroclor 1254 caused increasing liver residues above the controls but did not result in overt effects on morphological growth parameters during the nestling period in either starlings or red-winged blackbirds. However, we did observe significant differences in 2012 starling’s wing chord FA at day 10 and 13, and tarsus length FA between all treatment groups and controls, indicating the potential for PCB-induced stress. Nestling thyroid hormone profiles (T3) sampled throughout the nestling period supported developmental changes but did not reveal any differences among treatment groups. Starlings were subsequently reared in captivity and further tested during a simulated autumn migration. Migratory activity and orientation were tested using Emlen funnel trials over 6 consecutive weeks. Across treatment groups, we found a significant increase in mass, fat, and feather moult, and decreasing plasma thyroid hormones over time. At 12L:12D, control birds showed a peak in activity and a directional preference for 155.95° (South-southeast), while high-dosed birds did not. High-dosed birds showed a delayed directional preference for 197.48° (South-southwest) under 10L:14D, concomitant with apparent delays in moult. These findings link alterations in avian migratory behaviour to contaminant-specific mechanisms. Exposure to a ubiquitous environmental endocrine disruptor exerted only subtle short-term effects during the period of exposure but importantly, latent effects may be far more relevant for individual fitness. We discuss how the impacts of exposure during early stages of development were not significant for short-term nest success, but can still give rise to longer time-scale effects that are potentially relevant for survival and population stability for migratory birds.

Made available in DSpace on 2014-06-11T19:26:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-10-20Bitstream added on 2014-06-13T20:33:45Z : No. of bitstreams: 1 prando_l_me_jabo.pdf: 407609 bytes, checksum: 947cac68a18e2787e6a5c7039ce51656 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / As características comportamentais de uma espécie em processo de domesticação são muito importantes, pois a criação requer animais dóceis e sociáveis. Assim, torna-se necessário conhecer essas características, pois têm consequências relevantes no bem estar e desempenho das aves em cativeiro. O comportamento de reintegração social (CRS) pode ser avaliado em um labirinto de campo aberto observando-se sua aproximação ou não do animal da mesma espécie, no período de cinco minutos. Dessa forma, o objetivo desse trabalho foi avaliar o CRS em perdizes determinando-se as fontes de variação e os parâmetros genéticos para essa característica em animais criados em cativeiro. Foi realizada estatística multivariada, utilizando-se análise de fatores que revelou a existência de dois grupos distintos dentro da amostra analisada. Os componentes de (co) variância foram obtidos por inferência bayesiana usando máxima verossimilhança para as características do CRS, para dados não transformados e transformados. As características estudadas, sendo que as duas primeiras representam o grupo dos evitadores e as duas últimas, o grupo dos locomotores, foram parado no quadrante 1 (Pq1), parado no quadrante 4 (Pq4), andando no quadrante 1 (Aq1) e andando no quadrante intermediário (Aqi). As herdabilidades estimadas para as características Pq1, Pq4, Aq1 e Aqi foram respectivamente, 0,28; 0,43; 0,19 e 0,27 para os dados transformados. Assim, concluise que a seleção pode ser eficiente para alterar as médias destas características / Behavioral traits of a species in the process of domestication are very important, because raising the animal in captivity requires docility and sociability. Therefore, it is necessary to know these traits, because they have relevant consequences for the well-being and the performance of captive birds. The behavior of social reinstatement (CRS) can be evaluated in an open field maze by observing if the bird approachs or not to a conspecific, during five minutes. Thus, the aim of this study was to evaluate the CRS of red-winged Tinamou in order to determine the sources of variation and the genetic parameters of this trait in animals raised in captivity. We performed multivariate analysis, using factor analysis and it was revealed the existence of two distinct groups within the sample the movers and the avoiders. The (co) variances estimates were obtained by bayesian inference using the maximum likelihood, for transformed and non-transformed data. The studies traits were standing in quadrant 1 (Pq1), standing in quadrant 4 (Pq4), displacement behavior the quadrant 1 (Aq1) and displacement behavior in the intermediate quadrant (Aqi), where the first two represent the group of avoiders and the last two, the group of movers. The heritability means estimates for the traits Pq1, Pq4, Aq1 and Aqi were respectively 0.28, 0.43, 0.19 and 0.27 for the transformed data. Thus, we concluded that selection could be effective to change the means of these traits

Orientador: Sandra Aidar de Queiroz / Banca: Danísio Prado Munari / Banca: Patrícia Tholon / Resumo: As características comportamentais de uma espécie em processo de domesticação são muito importantes, pois a criação requer animais dóceis e sociáveis. Assim, torna-se necessário conhecer essas características, pois têm consequências relevantes no bem estar e desempenho das aves em cativeiro. O comportamento de reintegração social (CRS) pode ser avaliado em um labirinto de campo aberto observando-se sua aproximação ou não do animal da mesma espécie, no período de cinco minutos. Dessa forma, o objetivo desse trabalho foi avaliar o CRS em perdizes determinando-se as fontes de variação e os parâmetros genéticos para essa característica em animais criados em cativeiro. Foi realizada estatística multivariada, utilizando-se análise de fatores que revelou a existência de dois grupos distintos dentro da amostra analisada. Os componentes de (co) variância foram obtidos por inferência bayesiana usando máxima verossimilhança para as características do CRS, para dados não transformados e transformados. As características estudadas, sendo que as duas primeiras representam o grupo dos evitadores e as duas últimas, o grupo dos locomotores, foram parado no quadrante 1 (Pq1), parado no quadrante 4 (Pq4), andando no quadrante 1 (Aq1) e andando no quadrante intermediário (Aqi). As herdabilidades estimadas para as características Pq1, Pq4, Aq1 e Aqi foram respectivamente, 0,28; 0,43; 0,19 e 0,27 para os dados transformados. Assim, concluise que a seleção pode ser eficiente para alterar as médias destas características / Abstract: Behavioral traits of a species in the process of domestication are very important, because raising the animal in captivity requires docility and sociability. Therefore, it is necessary to know these traits, because they have relevant consequences for the well-being and the performance of captive birds. The behavior of social reinstatement (CRS) can be evaluated in an open field maze by observing if the bird approachs or not to a conspecific, during five minutes. Thus, the aim of this study was to evaluate the CRS of red-winged Tinamou in order to determine the sources of variation and the genetic parameters of this trait in animals raised in captivity. We performed multivariate analysis, using factor analysis and it was revealed the existence of two distinct groups within the sample the movers and the avoiders. The (co) variances estimates were obtained by bayesian inference using the maximum likelihood, for transformed and non-transformed data. The studies traits were standing in quadrant 1 (Pq1), standing in quadrant 4 (Pq4), displacement behavior the quadrant 1 (Aq1) and displacement behavior in the intermediate quadrant (Aqi), where the first two represent the group of avoiders and the last two, the group of movers. The heritability means estimates for the traits Pq1, Pq4, Aq1 and Aqi were respectively 0.28, 0.43, 0.19 and 0.27 for the transformed data. Thus, we concluded that selection could be effective to change the means of these traits / Mestre

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