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We investigated the molecular epidemiology, differential susceptibility to infection and disease, pathogenesis, diagnosis and treatment of avian mycobacteriosis in captive ringneck doves (Streptopelia risoria) and in the endangered white-winged duck (Cairina scutulata), both naturally infected with Mycobacterium a. avium. Our studies in doves demonstrated lower susceptibility to infection and less severity of lesions in the white color morph compared with the non-white. Genetic mechanisms of immunity to mycobacteriosis may be contributing or determining these differences. Given that the genes that code for white coloration are sex linked in birds, it is very likely that the gene or genes modulating this different immune response to M. a. avium infection in these doves could be associated to these loci or at least located in the same sexual (Z) chromosome, as the association with white color suggest. In the same birds, spleen biopsies followed by liver biopsies had the greatest potential for the diagnosis of mycobacteriosis by the demonstration of acid-fast organisms. Additional culturing of spleen or liver biopsies significantly increased the diagnosis of mycobacteriosis. The use of polymerase chain reaction (PCR) was the less sensitive techniques. Uneven distribution and low number of organisms in the liver, spleen and bone marrow may have contributed with the low diagnostic value of PCR. In a second group of sixteen doves with mycobacteriosis from the same flock, the combination of azithromycine, ethambutol and rifampin for 180 days was well tolerated but failed to cure them. Furthermore, this study demonstrated the inefficacy of liver biopsy to evaluate treatment as well the presence of antibiotic resistance in two isolates. These results highlight that erradication of mycobacteriosis in birds is not easy to achieve. Together with the possible emergence of antibiotic resistance in potentially zoonotic mycobacteria our results suggest that the treatment of mycobacteriosis in birds should not be recommended. Finally, the last study shows that white-winged ducks are highly susceptible to at least two sequevars of M. a. avium and that mycobacteriosis is a major threat to the ex situ conservation program. The minimal heterozygosis previously shown in these ducks could be contributing to this apparently ineffective immune response.

The roles of phylogeny and body size in avian heat stress physiology, and how they interact to set the upper limits to heat dissipation capacity, are largely unexplored. Determining thermal end points and maximum capacity for evaporative heat dissipation in species from diverse ecological guilds and evolutionary clades is vital for understanding species-specific vulnerability to future climatic scenarios. I measured evaporative water loss (EWL), resting metabolic rate (RMR) and body temperature (Tb) in three arid-zone passerines and three columbids of varying mass, namely the scaly-feathered weaver (Sporopipes squamifrons, ~11 g, SFW), sociable weaver (Philetairus socius, ~26 g, SW), white-browed sparrow weaver (Plocepasser mahali, ~40 g, WBW), Namaqua dove (Oena capensis, ~37 g, ND), laughing dove (Spilopelia senegalensis, ~89 g, LD) and Cape turtle dove (Streptopelia capicola, ~148 g, CTD) at maximum air temperatures (Ta) of 48–60°C. I found that evaporative water loss increased approximately linearly in all six species above a Ta of ~ 40 °C, which resulted in SFW, SW, WBW, ND, LD and CTD dissipating a maximum of 140, 220, 190, 498, 218 and 231 % of metabolic heat loads at the highest Tas respectively. All six species used facultative hyperthermia at high Tas and were able to regulate Tb up to and just beyond Tb = 45 °C. At the highest Tas experienced, passerines exhibited uncontrolled increases in Tb above 45 °C, resulting in 57, 100 and 100 % of SFW, SW and WBW respectively, reaching thermal limits at Ta = 48, 52 and 54 °C. Very few doves exhibited uncontrolled hyperthermia or reached thermal limits at their highest respective test Tas (Ta = 56, 68 and 60 °C in CTD, LD and ND respectively), suggesting that these birds could potentially survive higher Tas, and that lethal Tb was marginally higher than my conservative estimations. A conventional analysis found significant differences between doves and passerines in the slopes of EWL as well as the magnitude of the change in RMR, EWL and Tb between Ta = 35 and 48 °C. However, once phylogeny was controlled for, these differences were shown to be a result of phylogenetic inertia. Both a conventional analysis and a phylogenetic independent contrast (PIC) found a significant effect of body mass on slope of EWL, change in EWL (PIC only) and change in Tb between Ta = 35 and 48 °C. From the results of this study, I argue that by utilizing high ratios of cutaneous EWL to respiratory EWL, doves generate much less metabolic heat at high Tas than passerines. I suggest that larger passerines are better able to tolerate heat than smaller passerines, whereas the opposite is the case in doves. The lack of data from small doves obscured this finding in the conventional and PIC analyses. Further studies on the upper limits to the avian capacity for evaporative cooling and heat tolerance are critical for larger-scale mechanistic modeling of vulnerability to extreme heat events under current and future climate scenarios. / Dissertation (MSc)--University of Pretoria, 2014. / DST/NRF Centre of Excellence at the Percy FitzPatrick Institute (University of Cape Town) / University of New Mexico / Zoology and Entomology / MSc / Unrestricted

To ascertain potential ecological and landowner benefits of non-conventional agricultural systems, this project was designed to monitor cattle production and mourning dove (Zenaida macroura) utilization of land areas that allowed grazing cattle to harvest corn planted with no-till methods. In 2005-2008, study sites were located in four counties of MS, including four steer/heifer-grazed and harvested corn fields (SHS) and four conventionally-managed and combine-harvested corn fields (CHS). Vegetation characteristics, residual grain quantities, and use by doves were measured on SHS and CHS. Steer average daily gains (ADG), quality grades, and feedlot days were compared to traditional cattle production methods. Mourning dove numbers were greater on SHS than CHS during all study years and site locations (F=37.19, df=1, P=0.001). Biomass of residual corn kernels on the soil surface was greater on SHS compared to CHS in the fall (t=7.22, df=8, P= 0.001). Percentage coverage of grasses and forbs was greater in SHS than CHS in fall following harvest of corn with grass/forbs coverage being >10% in SHS and <5% in CHS. Throughout all seasons, percentage of bare ground was greater on CHS (50% - 80%) compared to SHS (1%-13%). Among average daily gains of grassed, corn-grazed, and feedlot fed cattle, a significant difference was detected (x2 = 8.45, df = 2, P = 0.002). Corn-grazed ADG was greater than bermudagrass-grazed but less than MS steers in the feedlot. Comparing conventionally-produced cattle of comparable characteristics to corned cattle used in my study, a significant decrease in feedlot days (Z =-1.83, P = 0.033) with no difference in quality grades of meat (Z = -0.65, P = 0.256) in no-till corn-grazed cattle was indicated. After offsetting costs of field preparation, fencing, and cattle maintenance, landowners using this production system can potentially increase income by at least $450/ha from fee/lease of corn fields for hunting and production of quality beef cattle.

This thesis presents the results of an examination conducted to determine the status of mourning doves in Throckmorton County, Texas.