Thesis (Ph.D.)--Memorial University of Newfoundland, 2000. / Includes bibliographical references.

Small, isolated populations can be at risk from genetic threats. In particular, inbreeding depression can threaten population viability, however the contribution of large-effect alleles to inbreeding depression in natural populations is largely unknown. Quantification of genetic threats requires estimation of the effective population size (Ne), which can be challenging given age-structure. Further, identification of large-effect alleles and estimation of Ne requires knowledge of a population's genetic mating system, which can itself be difficult to determine in populations with low genetic diversity. In this study, I quantified genetic threats to the small, isolated Scottish population of red-billed choughs (Pyrrhocorax pyrrhocorax), which is of high conservation concern, heightened by the recent occurrence of lethal blindness in nestlings. I first estimated extra-pair parentage rates to be low in Scottish choughs (~5% extra-pair offspring). I quantified inheritance patterns of blindness and found that the pattern of occurrence matched that expected for a single-locus recessive allele. Heterozygous carriers of the blindness allele are likely to be widely distributed in the population, limiting management options. Further, affected families had relatively larger broods than unaffected families, suggesting the blindness allele could persist in the population. Using a candidate gene approach, no consistent polymorphisms were found between blind and non-blind individuals in candidate gene amplicons and therefore a diagnostic marker for blindness could not be developed. I used demographic and genetic data to estimate Ne for Scottish choughs. Both demographic and genetic estimators suggested Ne is critically small (Ne≈30), such that future rates of loss of genetic variation will be high. The small Ne was largely due to high demographic variance, with high contributions to demographic variance from younger females and older males. Overall, this study adds to our understanding of genetic threats to small, wild populations and can thus inform management of threatened populations.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2000. / Bibliography: leaves 86-95.

Thesis (M. Sc.), Memorial University of Newfoundland, 1998. / Bibliography: leaves 110-121.

In social systems, the distribution of reproduction among group members is termed reproductive skew. This study was intended to address the issues of reproductive skew within the communally breeding smooth-billed ani employing genetic data to complement behavioural data. The aims of the study were: 1) to develop smooth-billed ani specific DNA markers to be used in the assessment of parentage 2) to determine parentage of buried eggs and surviving offspring to assess whether a reproductive skew pattern is seen 3) to comment on adult relatedness within smooth-billed ani groups. Smooth-billed ani microsatellite DNA sequences were isolated and characterized for use in a parentage/kinship analysis. Lambda Zap Express was used to construct a library of recombinant phage which was screened with TG and AAT probes. Five loci were characterized with between 4 and 9 alleles with heterozygosity values ranging from 0.538 to 0.840. The combined total exclusionary power of the five loci was 0.8869. Offspring loss due to egg destruction in the form of burial has been observed in smooth-billed anis. The issue of reproductive skew as a result of egg burial was addressed by estimating parentage of offspring both buried and remaining in the incubated clutch using 5 species specific microsatellite DNA markers. Evidence for an egalitarian system exhibiting very low skew was found. The significant factors affecting the potential for bias were laying order, laying timing and the number of breeding females. The relatedness of members within a social group may affect the amount of reproductive skew observed. Adults within nesting groups were tested for evidence of relatedness using the pedigree analysis program KINSHIP. Ten percent of dyads showed significant relationships. Low incidence of relatedness provided evidence that smooth-billed ani groups do not contain a large number ofyoung remaining at the natal nest nor was there evidence that regular dispersing within sibling units occurs. There was some evidence that a young male remained on his natal territory while a young female dispersed to a neighbouring territory. Low relatedness between adults and very low reproductive skew were consistent with the prediction of an egalitarian system / Thesis / Master of Science (MS)

Abstract Not Provided / Thesis / Master of Science (MSc)

Territorial behaviour is exhibited in cooperative breeders. The quality of defended territories can vary, and high-quality sites, which enhance fitness, should be used preferentially over poorer-quality sites. This study was intended to address issues of territory quality within the plural breeding, joint-nesting, smooth-billed ani (Crotophaga ani). I tested the communal joint-nesting threshold hypothesis, which posits that independent pairs will pay the price of group living if compensated by acquiring a superior territory. My results quantified differences in territory quality in terms of time of first breeding and chances for re-nesting or second-brooding. Per capita territory quality correlated negatively with group size, in conflict with the communal joint-nesting threshold hypothesis. Another hypothesis to explain communal behaviour is the habitat saturation hypothesis. This postulates that offspring remain in their natal territory and delay reproduction because of a local absence of suitable breeding habitat. I tested the habitat saturation hypothesis, which was developed to explain the evolution of group living in cooperatively breeding birds. I compared occupied ani territories with vacant sites, using eight ecological variables that may be important to the fitness of a group. In addition, I compared occupied territories with sites that were occasionally occupied. I did not find the habitat of our population of smooth-billed anis to be saturated. Some sites were never occupied because there are territory characteristics that presumably limit breeding. In contrast with expectations of habitat saturation, there were suitable sites available for breeding that were not in use. Results from both hypotheses presented suggest that there are not obvious group-living benefits and that one must consider other explanations for the evolution and maintenance of this system. / Thesis / Master of Science (MS)

In 1996 and 1997, I studied the nest site selection of the yellow-billed cuckoo (Coccyzus americanus) in the George Washington National Forest, southwestern Virginia. Data were collected from nine 30 ha plots. I compared the habitat features of nest sites with two types of nonnest sites (nonuse and systematically random). Habitat features were measured at 3 spatial scales: nest tree, nest tree area (0.0049 ha centered on the nest), and nest stand (forest stand surrounding the nest). Yellow-billed cuckoo nests were oriented in a nonrandom direction (mean angle = 114°, r = 0.43, P = 0.05) with respect to the bole and were concealed more from above than from below (n = 14, M = 5, p = 0.01) or from the side (n = 14, M = 4, p = 0.04). Slope aspect was nonrandom at yellow-billed cuckoo nest sites (mean angle = 143°, r = 0.52, P < 0.05). Small stem density in the nest tree area was greater (P = 0.029) at nest sites than nonuse sites but species composition was similar. The density of grape (Vitus spp.) and dogwood (Cornus spp.) snags was greater at nest sites than random sites (P < 0.001). Total basal area at yellow-billed cuckoo nest stands was lower than nonuse or random sites with (P = 0.033, and 0.016, respectively) or without (P = 0.014, and 0.004, respectively) snags. Nest sites also occurred in areas with less (P = 0.008) canopy cover but more (P = 0.038) ground cover than random sites. Yellow-billed cuckoos appeared to select nest sites based on the structure and composition of the understory vegetation. Periodic disturbance that promotes the growth of shade intolerant species, but maintains the general structure of the stand may be beneficial for this species that appears to select disturbed areas in mature forests. / Department of Biology

Thesis (M.Sc.)--Memorial University of Newfoundland, 1999. / Restricted until November 2000. Includes bibliographical references.

Wetlands of the Prairie Pothole Region (PPR) provide important breeding habitat for greater than 30 species of waterbirds. Approximately 70% of PPR wetlands have been lost since European settlement and remaining wetlands are subjected to frequent degradation, primarily due to agricultural activities. Horned grebes (Podiceps auritus) are experiencing long-term population declines and are listed as a species of Special Concern in Canada. Because there is virtually no information on the status and trends of pied-billed grebes (Podilymbus podicep) this species is also of considerable conservation concern. Grebes are recorded on the Waterfowl Breeding Population and Habitat Surveys (WBPHS) conducted annually in May by the Canadian Wildlife Service; however, how accurately these counts reflect actual abundance has been unknown. Using a repeated counts method in 2010 and 2011, estimates of detection probabilities averaged 0.48 and 0.18 for horned and pied-billed grebes, respectively. These results suggest that WBPHS ground surveys may be used as an efficient and effective management tool for monitoring horned grebe abundances. However, low detection rates for pied-billed grebes lend little support for including the species in future monitoring efforts using the WBPHS. I recommend that the Canadian Wildlife Service consider implementing standardized ground survey methods to facilitate annual monitoring of horned grebe abundances. Marshbird research has focused primarily on breeding habitat use or selection but has seldom examined how productivity is related to wetland characteristics. Understanding processes that affect distribution patterns and productivity of grebes could provide insights into actions needed to achieve conservation goals. Therefore, occupancy of wetlands by breeding and brood-rearing horned and pied-billed grebes was evaluated on 6-7 study sites (5.8-11.6 km2) in south-central Saskatchewan, 2010 and 2011, and related to wetland and upland habitat features. Wetland occupancy by grebes was influenced by interspecific competition as well as local and landscape-level wetland features. Horned and pied-billed grebes rarely co-occurred on smaller (≤4 ha) semi-permanent and permanent wetlands. At the wetland level, horned grebe occupancy and productivity were highly correlated with the amount of emergent vegetation, whereas wetland area alone was a better predictor of adult pied-billed grebe occupancy and productivity. At a landscape level, the number of semi-permanent, permanent, and artificial wetlands on each study site was an important predictor of breeding and brood-rearing wetland occupancy probability for horned grebes in 2010 and for pied-billed grebes in both years. However, breeding horned grebe occupancy probability and productivity were higher in low wetland density landscapes in 2011. Horned grebes may be opportunistic, exploiting more of the available wetland habitats in low wetland density landscapes during years of above-average water conditions. Conservation initiatives for grebes should consider the roles of wetland-specific and landscape-level features while protecting semi-permanent and permanent wetlands in landscapes characterized by both high and low wetland densities.