Nocera, Joseph J

In endotherms, physiological functioning is optimized within a narrow range of tissue temperatures, meaning that the capacity to dissipate body heat is an important parameter for thermoregulation and organismal performance. Yet, experimental research has found mixed support for the importance of heat dissipation capacity as a constraint on reproductive performance. To investigate the effects of heat dissipation capacity on organismal performance, I experimentally manipulated heat dissipation capacity in free-living tree swallows, Tachycineta bicolor, by trimming feathers overlying the brood patch, and monitored parental provisioning performance, body temperature, and offspring growth. I found that individuals with an enhanced capacity to dissipate body heat (i.e., trimmed treatment) provisioned their offspring more frequently, and reared larger offspring that fledged more consistently. Although control birds typically reduced their nestling provisioning rate at the highest ambient temperatures to avoid overheating, at times they became hyperthermic. Additionally, I examined inter-individual variation in body temperature within each treatment, and discovered that body temperature is variable among all individuals. This variability is also consistent over time (i.e., is repeatable), irrespective of treatment. Further, I found that individuals consistently differed in how they adjusted their body temperature across ambient temperature, demonstrating that body temperature is a flexible and repeatable physiological trait. Finally, I used a bacterial endotoxin (lipopolysaccharide) to examine the regulation of body temperature of captive zebra finches (Taeniopygia guttata) during an immune challenge. Exposure to lipopolysaccharide induces sickness behaviours, and results in a fever, hypothermia, or a combination of the two, depending on species and dosage. I asked what the relative role of different regions of the body (bill, eye region, and leg) is in heat dissipation/retention during the sickness-induced body temperature response. I found that immune-challenged individuals modulated their subcutaneous temperature primarily through alterations in peripheral blood flow, particularly in the legs and feet, detectable as a drop in surface temperature. These results demonstrate that the importance of regional differences in regulating body temperature in different contexts. Taken together, my thesis demonstrates that heat dissipation capacity can affect performance and reproductive success in birds.

Author Keywords: body temperature, heat dissipation, tree swallow, zebra finch

I implemented three hayfield management regimens in southern Ontario (a typical schedule at the farmer`s discretion, a delayed first harvest after July 14, and an early first harvest before June 1 with 65 days before second harvest), and evaluated the costs/benefits to farmers regarding hay quality and feasibility, and to Bobolinks (Dolichonyx oryzivorus) regarding reproductive activity and phenology. Typical management resulted in little to no Bobolink reproductive success, and early harvested sites were not (re)colonized. On delayed harvest sites Bobolinks experienced high reproductive success, but hay quality fell below ideal protein levels for most cattle before harvest. I also examined the habitat features Bobolinks use as the basis for establishing territories and associations between Bobolink territory size and habitat quality. I compared vegetation structure, patch size, and prey abundance between small and large territories. Small territories typically occurred on smaller fields with more preferred vegetation characteristics and greater prey abundance.

Author Keywords: agro-ecosystem, Bobolink, Dolichonyx oryzivorus, grassland birds, hayfield management

The distribution of animals is rarely random and is affected by various environmental factors. We examined space-use patterns, habitat selection and stress responses of whip-poor-wills to mining exploration activity.To the best of my knowledge, fine scale patterns such as the habitat composition within known home ranges or territories of eastern whip-poor-wills have not been investigated. Using a population at the northern edge of the distribution in an area surrounding a mining exploration site, we tested whether variations in habitat and anthropogenic disturbances influence the stress physiology of individuals. We found no effect of increased mining activity on the stress physiology of birds but found a significant scale-dependent effect of habitat on their baseline and stress-induced corticosterone levels, and we suggest that these are the result of variations in habitat quality. The importance of other factors associated with those habitat differences (e.g., insect availability, predator abundance, and microhabitat features) warrants further research.

Author Keywords: anthropogenic disturbances, Antrostomus vociferus, corticosterone, eastern whip-poor-will, habitat selection, radio-­telemetry

I investigated the impact of beef-cattle farm management on the reproductive success of Bobolink (Dolichonyx oryzivorus) and Eastern Meadowlark (Sturnella magna) within Eastern Ontario. I monitored rotational grazing management regimes and hay cut dates while assessing breeding phenology and reproductive success of Bobolinks and Eastern Meadowlarks. In pasture paddocks the major factor determining Bobolink reproductive success was the date that cattle entered a paddock to graze, with earlier entries resulting in lower reproductive success. On a landscape scale, within a series of paddocks grazed by a single herd, as the number of paddocks grazed during the nesting season increased, the number of Bobolinks that reproduced successfully decreased. Experimental quantification of trampling showed that cattle exposure to clay pigeon targets, regardless of stocking rates, resulted in the majority of targets being trampled. In hayfields associated with beef- cattle operations, grassland birds had a higher likelihood of success when cutting occurred after 4 July. The best method to improve the reproductive success of Bobolinks and Eastern Meadowlarks is to leave some hayfields and pasture paddocks undisturbed until nesting is complete.

Author Keywords: Bobolink, Dolichonyx oryzivorus, farm management, hayfield, pasture, rotational grazing

Detecting relevant and meaningful patterns from the complex, interconnected network of relationships between organisms and their environment is a primary objective of ecology. Ecological patterns occur across multiple scales of space and time. In this dissertation, I examine aspects of environmental structure that influence a species' distribution and are expressed in that species' population dynamics. I compare the morphology of the five-lined skink (Plestiodon fasciatus) near its high latitude range limits with a lower latitude population and evaluate the economics of their behaviour in the context of its reproductive strategy. I tested the conformity of this species to biogeographical rules postulated by MacArthur, Bergmann, and Rensch. Spatial ecology was investigated in the context of the environmental potential for polygamy proposed by Emlen and Oring (1977) The five-lined skink, Plestiodon fasciatus, conformed to these biogeographic rules. Specifically, abiotic factors were the primary limiting factors affecting distribution at the high latitude range limits of the species; body size was larger in high latitude populations; and the degree of sexual size dimorphism was greater at high latitude than at low latitude. Spatial ecology at the individual scale was influenced by sites with suitable thermal conditions which facilitate the polygynandrous mating system documented in P. fasciatus in high latitude populations. My results confirm the importance of microsites with suitable thermal profiles as key habitat for ectothermic vertebrates at high latitudes. The influence of temperature as a limiting abiotic factor is expressed in population density, body size, spatial ecology, and reproductive strategy of P. fasciatus. Conservation and restoration of high latitude populations of ectothermic vertebrates should focus on ensuring thermal requirements of the species of concern are met before other factors are addressed, as temperature is likely the single most important limiting factor at high latitude range limits.

Author Keywords: biogeography, lizard, Plestiodon fasciatus, range limits, sexual size dimorphism, spatial ecology

I examined Bank Swallow (Riparia riparia) colony persistence and occupancy, in lakeshore, river and man-made aggregate pit habitat. Habitat persistence was highest on the lakeshore and lowest in aggregate pits, likely due to annual removal and relocation of aggregate resources. Bank Swallow colonies in aggregate pit sites were more likely to persist if a colony was larger or if burrows were located higher on the nesting face. I also compared nest productivity and health factors of Bank Swallows in lakeshore and aggregate pit habitats. While clutch size was the same in both habitat types, the number of fledglings from successfully hatched nests was significantly higher in aggregate pit sites than from lakeshore sites. Mass of fledgling Bank Swallows did not differ significantly between habitat types, however mass of adults from aggregate pits decreased significantly over the nesting season. Parasite loads on fledgling Bank Swallows were significantly lower in aggregate pits than in lakeshore sites. According to these indicators, aggregate pits appear to provide equivalent or higher quality habitat for Bank Swallows than the natural lakeshore sites, making them adequate and potentially key for this species' recovery. Aggregate pit operators can manage for swallows by (1) creating longer, taller faces to attract birds and decrease predation, and (2) supplementing their habitat with water sources to encourage food availability.

Author Keywords: Aerial insectivore, aggregate pits, Bank Swallow, colony persistence, ectoparasites, substitute habitat

Resources and risk are in constant flux and an organism's ability to manage change may improve their likelihood of persistence. I examined intra-seasonal variation in nest-site selection and survival of a declining wetland bird, the Black Tern (Chlidonias niger surinamensis). I modelled nest site occupancy and survival of early and late-nesting birds as a function of static and dynamic factors. Early-nesting birds selected nest sites based on the degree and direction of habitat change that occurred over the nesting cycle, while late-nesting birds selected sites based on static conditions near the time of nest-site selection. Nest age had the strongest influence on daily survival rate for both early and late-nesting birds, but the shape of this relationship showed intra-seasonal differences. Additionally, early-season survival improved slightly with increasing vegetation coverage and distance between conspecific nests, while late-season survival increased with clutch size. My results suggest that intra-seasonal variation in nest-site selection and survival is driven by changing habitat conditions and predator behavior.

Author Keywords: Black Tern, Chlidonias niger surinamensis, daily survival rate, intra-seasonal variation, nest-site selection

Drivers of North American Barn Swallow population declines are not well understood, but foraging habitat loss is thought to be a contributing factor. Determining patterns of habitat use is challenging for swallows because they move rapidly but are too small to carry GPS tags. We showed that automated radio-telemetry could be used to track the movements of swallows with enough accuracy (median error 250 m) to monitor local habitat use. We then combined information on breeding Barn Swallows habitat use, land cover, aerial insect abundance, and fledging success to test for a link between foraging habitat quality and reproductive success. Foraging activity was concentrated within 600 m of nest sites and varied with land cover; however, responses to land cover were not consistent across birds. Aerial insects were most abundant near wetlands and least abundant near open water and over cropland. Consistent with a link between foraging habitat and reproductive success, nests in barns with more wetland and less open water within 1 km, and with less field area within 2 km occupied by row crops, on average fledged more young swallows.

Author Keywords: aerial insectivores, automated telemetry, habitat use, land cover, movement, nest success

Barn Swallow (Hirundo rustica) populations have declined in North America over the past 40 years and they are listed as Threatened in Ontario, Canada. Changes in the food supply have been hypothesized as a potential cause of this population decline. I used DNA barcoding to investigate the diet and food supply of Barn Swallows and to determine if the food supply affects their reproductive performance. In two breeding seasons, I monitored nests, collected fecal samples, and monitored prey availability by collecting insects from the habitat surrounding breeding sites using Malaise traps. I used DNA barcoding to identify insect specimens collected from the habitat and to identify prey items from Barn Swallow nestling fecal samples. I found that Barn Swallow nestlings were fed a very broad range of prey items but were fed larger prey items more frequently. Prey availability was not related to the timing of reproduction, the number of nests at a breeding site, or the reproductive output of individual nests. This study provides information on the diet composition of Barn Swallows in North America and suggests that food limitation during the breeding season may not be a major factor in their population decline.

Author Keywords: aerial insectivore, diet, DNA barcoding, Hirundo rustica, metabarcoding, reproductive success

Chimney swifts are listed as Threatened nationally and in many provinces within Canada due to rapid population declines. I examined large-scale spatial variation in the maximum size of chimney swift roosts at the northern edge of their range to identify where larger roosts occur. I used multi-sourced data collected across Ontario and Quebec between 1998 and 2013. I found that larger roosts were found at more northerly latitudes, and that very large roosts (>1000 birds) only occurred north of 45°. I also investigated fine-scale patterns of chimney swift positioning inside one of the largest roosts in Ontario. Using digitally recorded images, I calculated the angular position of swifts inside the roost relative to ambient and roost temperature. I found that swifts showed a strong preference for clinging to the south facing wall and clustered more when ambient air temperature was warmer. Thus, huddling in swifts provides additional or alternate benefits, other than serving purely to reduce costs of thermoregulation at low ambient temperatures. This research contributes to the understanding of chimney swift roosting ecology and identifies large roosting sites that should be retained for conservation.

Author Keywords: chimney swift, communal roosting, conservation, group size, social thermoregulation, species-at-risk