Lindgren, Staffan

Urbanization is considered one of the greatest human-caused threats to biodiversity. Human development and encroachment on native habitats and its impacts on species, however, is nuanced; while it has been found to create detrimental impacts on some species, certain aspects of urbanization may benefit others. This interaction of advantages vs constraints offered by urban landscapes is especially relevant to species that show sufficient behavioural plasticity to settle in this rural/urban interface. The objective of this thesis is to investigate some of these potential costs/benefits of urbanization in mountain chickadees. I first assess a potential positive effect of urban settlement noted in other systems – a decrease in the incidence of nest ecotparasites found in urban landscapes - in mountain chickadees nesting in Kamloops, BC, Canada. I enumerated the blowflies and fleas found in collected nests in 2019 and 2020 to determine whether nest parasitism differs between urban and rural habitats in the region, and whether this in turn influences nest success (Chapter 2). I found that abundance of blow fly puparia was higher in rural nests, but that flea abundance was associated with temperature and not urbanization. Additionally, I observed that urban nests fledged approximately one additional chick per nest. This suggests urban habitats could lift some constraints that would normally decrease nestling condition. I then compared rates of adult chickadees feeding nestlings to determine whether differences in ectoparasitism levels between habitats results in compensatory feeding by parents, and if this affected the growth rate of nestlings (Chapter 3). I did not find evidence that urbanization or ectoparasite abundance influenced parental feeding or growth rate. I did find that feeding rate was lower and that growth rate was higher in warmer years. Other studies showing potential differences in prey availability between habitats, with rural sites having potentially greater abundance of prey, may help explain my results – while prey might be more abundant in one habitat, nestling condition may be less affected by parasite infestation in the other, helping balance the costs/benefits of settlement between habitats. While my results provide some evidence that reduction of parasites in urban areas can benefit urban settling species, further research will be required to determine the mechanism that causes this phenomenon.

The strategic allocation of resources to maximize fitness is the organizing principle shaping the evolution of life histories. The physiology and behaviour of animals is a manifestation of trade-offs in resource allocation among traits and activities that benefit current or future reproduction. In theory, traits subject to such trade-offs are expected to show negative correlations, but numerous field studies have documented apparent contradictions to theoretical expectations: in some populations, parental effort (allocation to current reproduction) and reproductive performance (i.e., a fitness component) are not negatively correlated to self-maintenance (allocation to future reproduction). One explanation for such findings is that inter-individual variation in resource acquisition can obscure trade-offs by altering the overall quantity of resources individuals are able to invest. Acquisition may influence both the quantity of resources allocated in trade-offs as well as reproductive success. Asymmetries in acquisition may be the product of differences in intrinsic quality (individual phenotypes) and/or environmental factors (territory quality). In a population of breeding mountain bluebirds (Sialia currucoides), I sought to determine how resource acquisition varied, and to identify how it may affect life-history trade-offs and reproductive performance. In my research, I used several lines of inquiry to characterize how resource acquisition varies and affects trade-offs in the study population. First, I showed that offspring quality, a contributor to fitness, is influenced by the types of prey nestling bluebirds are fed by their parents, and that the resources parents provide to their broods vary seasonally and as their nestlings age. Next, I used a short-term manipulation of brood age to find that parents have limited flexibility in their capacity to acquire resources while provisioning broods, which may be due to intrinsic or extrinsic constraints. I then identified relationships among the landscape characteristics of breeding territories (extrinsic factors, potentially influencing acquisition) and the reproductive performance of bluebirds, over an 11-year period. These characteristics, elevation and distance to forest edges, are subsequently linked to differences in microclimate, microhabitat, and parental prey use, providing a partial explanation for why occupancy and reproductive success are spatially clustered and consistent over time. Finally, I used a brood size manipulation to induce changes in parental effort, revealing that acquisition (quantified as both individual and territory quality) influences how mountain bluebirds trade-off one proxy for self-maintenance (energy metabolites) with providing food to their offspring. Interestingly, these effects differed between the sexes. Females generally biased allocation towards current reproduction, increasing provisioning to larger broods, regardless of territory quality; females on low-quality territories subsidized increased provisioning activity by catabolizing stored resources. In contrast, only males on high-quality territories increased parental effort in response to larger broods, and among these individuals, only high-quality males incurred an energy deficit to subsidize this activity. My findings showed that resource acquisition may be critical to understanding why trade-offs differ among individuals, and that both intrinsic and extrinsic limits on acquisition may influence the patterns of allocation we observe in wild populations.

The Chun T’Oh Wudujut is a provincial park located in the Interior Cedar-Hemlock biogeoclimatic zone. My objective was to assess the use of carabid beetles as bioindicators of change in this unique interior temperate rain forest ecosystem. Using a combination of morphotyping and DNA barcoding, I examined the diversity of carabid beetles in three different habitat types: clear-cuts, undisturbed old growth, and disturbed old growth subject to frequent human traffic. Nineteen species of carabid were observed, with the highest diversity occurring in clear-cut sites. Carabid diversity in both old growth habitats was similar, but differed from that in the clear-cuts. Temperature and relative humidity proved more variable in clear-cut sites; this may impact carabid biodiversity, and should be measured in future bioindicative studies. Several species of carabid beetles (alone and in combination) were identified as possible bioindicators, including Scaphinotus marginatus, Trechus chalybeus, Pterostichus herculaneus, and Pterostichus riparius.