Biology

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A comparison of seasonal flexibility in pectoralis muscle fiber type and enzyme activity in migratory and resident sparrow species
(Journal of Experimental Biology, 2024-02) Lewicki, Louisa M.; Zhang, Marina; Staples, James; Guglielmo, Christopher G.; Ivy, Catherine
The pectoralis muscle in birds is important for flight and thermogenesis. In migratory songbirds this muscle exhibits seasonal flexibility in size, but whether this flexibility reflects changes in muscle fiber type has not been well documented. We investigated how seasonal changes in photoperiod affected pectoralis muscle fiber type and metabolic enzymes, comparing among three closely related sparrow species: two seasonal migrants and one year-round, temperate climate resident. We quantified fast oxidative glycolytic (FOG) and fast glycolytic (FG) fibers histologically, and measured activities of citrate synthase (CS) and lactate dehydrogenase (LDH) in the pectoralis muscle of the three species that were acclimated to long or short periods of daylight. In all species, FOG was the predominant fiber type, but song sparrows had FG fibers regardless of daylight conditions. By contrast, Lincoln's sparrows incorporated FG fibers only under short-daylight conditions, and house sparrows did not significantly express FG fibers, regardless of daylight length. Both migratory species increased LDH activity in short-daylight conditions but did not alter CS activity. In contrast, resident house sparrows did not alter CS or LDH activity with changes in daylight length. Our findings suggest that the presence of FG fibers is important for seasonal flexibility in LDH activity. Additionally, migratory species exhibited seasonal flexibility in muscle fiber type and enzyme activity, presumably to support migratory flight, while the resident species did not exhibit such seasonal flexibility, suggesting that this consistent phenotype is important year-round, despite changing thermogenic requirements.
Collar? I barely know her: The utility of accelerometry in measuring personality in situ for a free-ranging wild mammal
(Elsevier, 2025-01-10) Sanders, Jonas; Studd, Emily; Dantzer, Ben; Wishart, Andrea; Gaidica, Matt; Ruckstuhl, Kathreen; Boutin, Stan; Lane, Jeffrey; Martinig, April Robin
The study of personality in animals requires methods for quantifying consistent among-individual differences in behaviour. Typically, standardized behavioural assays are used rather than in situ tools. We evaluated whether assays and accelerometry, a relatively novel method of quantifying animal behaviour in the field, yielded similar personality measurements in a wild population of North American red squirrels, Tamiasciurus hudsonicus, by comparing among-individual correlations of behaviours across these methods. Both methods described two behavioural axes, with assays capturing activity and exploration, and accelerometry capturing foraging and movement. We found higher trait repeatability (R) for traits measured with assays (Radj: adults: 0.37–0.40; yearlings: 0.18–0.48) than for traits measured with accelerometry (Radj: adults 0.11–0.19; yearlings: 0.07–0.11). Additionally, we found a significant positive among-individual correlation between the assay behavioural axis associated with exploration and the accelerometry behavioural axis associated with foraging. We also found that the repeatability of traits measured with accelerometry was related to the amount of behavioural data captured by this method. Given that accelerometry was able to quantify animal personality in situ for adults, accelerometer collars may present a possible alternative to assays for species in which assays are impractical. Our results also underscore the importance of considering the amount of behavioural data captured by different methods when assessing trait repeatability. As researchers strive to measure behavioural variation under natural conditions, sufficient behavioural sampling remains a priority.
Migration strategy and constraint in migration behavior vary among shorebird species with different life histories
(Wiley, Ecological Society of America, 2025-01-15) Clements, Sarah J.; Loghry, Jason P.; Linscott, Jennifer; Ruiz, Jorge; Gunn, Joe; Navedo, Juan G.; Senner, Nathan; Ballard, Bart; Weegman, Mitch
Migration strategy is a key behavioral characteristic guiding how migratory species time their annual cycles and use habitat. Understanding variation in migration strategy within and among species and individuals can be useful for understanding how birds navigate energetic trade-offs and designing or modifying conservation plans meant to benefit multiple species and life histories. We compared migration strategies among three migratory shorebird species with variable life history traits and short, medium, and long migration distances, respectively: American avocets (Recurvirostra americana), black-bellied plovers (Pluvialis squatarola), and Hudsonian godwits (Limosa haemastica). Avocets (short distance) exhibited the most within-species variation in migration duration, proportion of migration time spent at stopovers, and stopover duration. Plovers (medium distance) and godwits (long distance) showed less variation in these metrics, but godwits showed the most variation in the number of stopovers used. There were significant differences among species in migration distance, number of stopovers used, proportion of time stopped over, departure and arrival dates, and migration duration, but not mean stopover duration. We also found that avocets spent more time stopped over relative to migration distance than plovers or godwits, indicating that avocets showed the most energy-minimizing strategy of the three species. Our findings set the stage for future work assessing the effects of climate change and land use on characteristics associated with different migration strategies for additional migratory species.
Effect of snow cover on the off-host survival of Dermacentor variabilis (Acari: Ixodidae) larvae
(Journal of Medical Entomology, 2024-01) Diyes, Chulantha P; Yunik, Matthew E M; Dergousoff, Shaun J; Chilton, Neil
The geographical range of the American dog tick, Dermacentor variabilis (Say), in Canada continues to expand northwards into areas with colder winter temperatures. Understanding what influences the off-host survival of D. variabilis over winter is important for predicting the northern distributional limit of this species. A field experiment was conducted to determine the effect of snow cover on the off-host survival of unfed D. variabilis larvae from a population situated near the northern distributional limit in Saskatchewan, Canada. Ticks were placed in tubes within 1 of 9 field enclosures (tickaria) in early fall. The 9 tickaria were divided into 3 equal treatment groups: no snow cover, natural snow cover (maximum depth of 25 cm) and extra snow cover (maximum depth of 32 cm). Tick survival was measured in mid-winter and in early spring (i.e., ~17 and ~26 wk after start of experiment). The results showed that snow cover had a significant impact on the relative humidity, but not temperature, in the tickaria. Larvae in tickaria with no snow cover had a higher mortality rate (27%) than larvae in tickaria with natural snow cover (6%) or extra snow cover (4%). Although snow cover enhanced off-host survival, many individuals were able to survive in sub-zero temperatures under leaf litter in the absence of continuous snow cover for a period of 108 days. These findings have implications for the construction of predictive models to determine the northern distributional limits of D. variabilis, a species that is an important vector of several pathogens.
Comparison of the supercooling points of questing Dermacentor variabilis adults in two populations on the Canadian prairies and implications for overwinter survival
(Springer Nature, 2023-12-12) Yunik, Matthew Edward Marks; Diyes, Chulantha P.; Chilton, Neil
A comparison was made of the supercooling points (SCPs) of questing Dermacentor variabilis adults from two populations located ca. 800 km apart on the Canadian prairies. This is also the first study to examine whether there are seasonal fluctuations in the SCP of questing D. variabilis adults. The SCPs of adult ticks from Lizard Lake Community Pasture, a recently established population in west-central Saskatchewan, varied over spring and summer, with the median SCP warming over time. In addition, the SCPs of ticks from Lizard Lake Community Pasture were significantly higher than those of adult ticks collected from Sandy Hook in Manitoba, a population that has been established for decades. The off-host survival of adults from Sandy Hook between summer and spring has been shown previously to be significantly greater than that of adults from Lizard Lake Community Pasture. The findings of the present study suggest that there may be geographical variation in the SCPs of D. variabilis adults which may be associated with differences in overwinter survival. The relatively low SCPs of questing D. variabilis adults, and the ability of some adults to survive off-host during winter, may be factors contributing to the range expansion of this tick species in Canada.
Comparison of flea diversity in the burrows of Richardson’s ground squirrels (Urocitellus richardsonii) in an urban and rural site in central Saskatchewan, Canada
(Journal of Vector Ecology, 2024-09-20) Thoroughgood, Jessica T; Chilton, Neil B
Spatial and temporal differences in the relative abundance of arthropod vectors is an important factor influencing the risk of disease for mammalian hosts. Seasonal changes in the diversity and abundance of fleas (Siphonaptera) in Richardson's ground squirrel (Urocitellus richardsonii) burrows were studied at two sites in central Saskatchewan. A total of 225 fleas (151 at an urban site and 74 at a rural site) were collected. Flea prevalence differed among seasons at the urban site, but not at the rural site. Of the nine flea species detected (8 at the urban site and 6 at the rural site), Oropsylla rupestris, O. bruneri, O. labis, O. tuberculata and Aetheca wagneri are vectors of Yersinia pestis, the causative agent of plague. The presence and abundance of some fleas differed between sites and seasons. Neopsylla inopina and O. rupestris were the most abundant species at the urban site during the spring and summer (respectively), while O. bruneri was the most abundant species at the rural site. Our findings may have implications for the management of the black-tailed prairie dogs (Cynomys ludovicianus) in south-western Saskatchewan because they coexist with U. richardsonii, are hosts for Oropsylla, and are at great risk of plague exposure/infection.
Risk-Taking in Bluebirds After Exposure to a Nest Predator Relates to Parental Roles and Shows Little Cooperation Between Partners
(Ethology: International Journal of Behavioural Biology, 2024-11-27) Wiebe, Karen; Tkaczyk, Simon P.
Parents may experience a trade-off between caring for offspring and protecting themselves from predators. The reproductive value hypothesis predicts that parents should take more risks for older, more valuable, offspring whereas the harm to offspring hypothesis predicts that parents should risk more for vulnerable offspring that would suffer most from a lack of parental care at the moment. After exposing parent mountain bluebirds (Sialis currucoides) to a model predator, we recorded latency times for them to touch, to look into, and to enter their nestbox and the number of times they inspected the box across three breeding stages: nest-building, incubation and nestling-rearing. Females took greater risks than males during the nest-building and incubation stages by inspecting and entering boxes sooner and more times, consistent with their role in parental care at those early breeding stages that requires them to enter the box. Risk-taking in males was consistent with the reproductive value hypothesis, increasing across breeding stages. In contrast, females took the greatest risk during incubation, consistent with the harm to offspring hypothesis. Furthermore, latency to look into the box was not correlated between pair members and both sexes assumed the risk to first inspect the nestbox approximately equally. This suggests there is not a "war of attrition" between mates over risk-taking but neither was there cooperation by the male to facilitate the rapid resumption of parental care by his mate. The results highlight that patterns of investment in nest defense in birds may be sex-specific.
In-reservoir transformation of dissolved organic matter as a function of hydrological flow
(Journal of Environmental Management, 2024-01) Imtiazy, Md Noim; Hunter, Kristine; Hudson, Jeff J
Reservoirs are vital to meet the ever-increasing demands for freshwater in a warming climate. Dissolved organic matter (DOM) represents an important pool of carbon and can be a major concern in drinking water sources. However, insights into DOM dynamics in temperate, semi-arid reservoirs remain limited. Therefore, we investigated the variations in DOM properties in Lake Diefenbaker, a large reservoir on the Canadian Prairies, by analyzing eight years of DOM concentrations and composition through linear mixed effect modeling. Contrary to expectations, reservoir dissolved organic carbon (DOC) concentration showed no correlation with inflow from the South Saskatchewan River (p = 0.12), while dissolved organic nitrogen (DON) increased with decreasing inflow (p = 0.002). DOM optical indices (SUVA254 and E4:E6 ratio) and DOC:DON ratio revealed a pronounced influence of inflow on reservoir DOM composition (p < 0.001), i.e., allochthonous characteristics increased with increasing flow, and autochthonous characteristics increased with declining flow. Travel time corrected comparison of approximately the same water parcel along the reservoir length revealed that increasing water residence time in downstream regions led to a significant transformation in DOM composition, favoring autochthonous characteristics (mean SUVA254 reduced by 0.52 L mg-C−1 m−1, and the E4:E6 and spectral slope ratio increased by 1.6 and 0.06, respectively). Autochthonous DOC inputs likely offset the allochthonous DOC losses, which resulted in a relatively stable DOC concentration throughout the reservoir (mean 3.7 mg L−1). Additionally, the effect of a large aquaculture operation on reservoir DOM properties was investigated, but no effect was detected. The results have significant implications for managing large river-reservoirs. Autochthonous DOM poses challenges to water processing, necessitating monitoring of DOM composition for reservoir drinking water quality. Insights on climate-induced changes in DOM properties will also assist with understanding changes to habitat conditions and contaminant transport.
Has lake brownification ceased? Stabilization, re-browning, and other factors associated with dissolved organic matter trends in eastern Canadian lakes
(Water Research, 2024-11) Imtiazy, Md Noim; Paterson, Andrew; Higgins, Scott; Yao, Huaxia; Houle, Daniel; Hudson, Jeff J
The increase in dissolved organic carbon (DOC) concentrations in freshwater systems has received considerable attention due to its implications for drinking water treatment and numerous limnological processes. While past studies have documented the influence of recovery from acidification and climate change on long-term DOC trends, the emerging importance of these explanatory factors remains less understood. In addition, few studies have followed up on recent trends in sites that have undergone increases in DOC. Using a dataset from 1980 to 2020, we investigated interannual variations in DOC and dissolved organic nitrogen (DON) in 49 lakes across four eastern Canadian regions with a history of increases in DOC. We identified recent shifts in DOC patterns using LOESS smoothing and piecewise regression. We observed a stabilizing pattern or even a decrease (p < 0.001) in high acidification regions (Dorset and Nova Scotia), where increases in DOC were previously documented. At the low acid deposition region, IISD-Experimental Lakes Area, an increasing pattern in DOC stabilized in the early 2000s; however, DOC appears to be increasing again in recent years (p = 0.03). Our analysis identified precipitation and SO4 deposition as the primary explanatory variables for DOC patterns (explaining 56–71% of variance). However, because acid deposition has declined substantially, climate and local watershed factors are becoming increasingly influential, leading to the emergence of new DOC patterns. Long-term changes in DOC and DON were not always synchronous, as these were often correlated with different factors (e.g., DON with ammonium deposition). This resulted in observable shifts in DOC:DON ratios, indicative of changes in dissolved organic matter (DOM) composition. We underscore the importance of ongoing monitoring in diverse regions because of the changing nature of environmental variables and new emerging trends.
Species traits predict the aryl hydrocarbon receptor 1 (AHR1) subtypes responsible for dioxin sensitivity in birds
(Nature Portfolio, 2020) Bianchini, Kristin; Morrissey, Christy
Differences in avian sensitivity to dioxin-like compounds (DLCs) are directly attributable to the identities of amino acids at two sites within the ligand binding domain (LBD) of the aryl hydrocarbon receptor 1 (AHR1). Recent work suggests that by influencing avian exposure to naturally occurring dioxins, differences in diet, habitat, and migration may have influenced the evolution of three AHR1 LBD genotypes in birds: type 1 (high sensitivity), type 2 (moderate sensitivity), and type 3 (low sensitivity). Using a boosted regression tree (BRT) analysis, we built on previous work by examining the relationship between a comprehensive set of 17 species traits, phylogeny, and the AHR1 LBD across 89 avian species. The 17 traits explained a combined 74% of the model deviance, while phylogenetic relatedness explained only 26%. The strongest predictors of AHR1 LBD were incubation period and habitat type. We found that type 3 birds tended to occupy aquatic habitats, and, uniquely, we also found that type 3 birds tended to have slower developmental rates. We speculate that this reflects higher evolutionary exposure to naturally occurring dioxins in waterbirds and species with K-selected life histories. This study highlights the value of trait-based approaches in helping to understand differing avian species sensitivities to environmental contaminants.
The relative contribution of individual quality and changing climate as drivers of lifetime reproductive success in a short‑lived avian species
(Nature Portfolio, 2020) Berzins, Lisha L.; Dawson, Russell D.; Morrissey, Christy; Clark, Robert
Animal populations are influenced strongly by fluctuations in weather conditions, but long-term fitness costs are rarely explored, especially in short-lived avian species. We evaluated the relative contributions of individual characteristics and environmental conditions to lifetime reproductive success (LRS) of female tree swallows (Tachycineta bicolor) from two populations breeding in contrasting environments and geographies, Saskatchewan and British Columbia, Canada. Female swallows achieved higher LRS by breeding early in the season and producing more fledglings. Other measures of female quality had virtually no influence on LRS. Genetic factors did not predict LRS, as there was no correlation between life-history components for sister pairs nor between mothers and their daughters. Instead, climate variability—indexed by spring pond density (i.e., abundance of wetland basins holding water) during years when females bred—had strong positive effects on female LRS in more arid Saskatchewan but only weak positive effects of moisture conditions were detected in wetter British Columbia. Overall, several life history trait correlates of LRS were similar between populations, but local environmental factors experienced by individuals while breeding produced large differences in LRS. Consequently, variable and extreme environmental conditions associated with changing climate are predicted to influence individual fitness of distinct populations within a species’ range.
Spatio-Temporal Patterns of Crops and Agrochemicals in Canada Over 35 Years
(Frontiers Media SA, 2020) Malaj, Egina; Levi, Freistadt; Morrissey, Christy
In an effort to feed a growing world population, agriculture has rapidly intensified over the last six decades, relying heavily on agrochemicals (fertilizers, insecticides, fungicides, and herbicides) to increase and maintain desired crop yields. Despite environmental concerns in Canada’s agricultural regions, long-term patterns of changing crops and the associated trends in the proportion of cropland treated with agrochemicals are poorly documented. Using the Canadian Census of Agriculture, we compiled historical data over 35 years (eight census periods: 1981–2016) on agrochemical applications, measured as the proportion of cropland treated with pesticides and fertilizers and the associated crop classes, to identify and interpret spatial and temporal trends in Canada’s agricultural practices across 260 census units. Due to differences in agricultural practices, soil, and climatic conditions across the country, the Pacific (British Columbia), Prairie (Alberta, Saskatchewan, Manitoba), Central (Ontario, Quebec), and Atlantic (Nova Scotia, New Brunswick, Newfoundland/Labrador, Prince Edward Island) regions were analyzed separately. Most of the agrochemicals in Canada were applied in the Prairie and Central regions, which combined comprise 97% of the total cropland. Fertilizers were the dominant agrochemicals across Canada applied on 48% (Pacific) to 78% (Prairie) of the total cropland area, followed by herbicides, which were applied on 30% (Pacific) to 81% (Prairie) of the total cropland area in 2016. Notably, we observed significant changes between 1996 and 2016 in area treated with fungicides and insecticides, which increased by 412% and 50% in the Prairie region and by 291% and 149% in the Central region, respectively. The proportion and distribution of crops shifted in favor of more oilseeds and soybeans in the most intensive Prairie and Central regions, whereas cereals decreased over the same time period. Our analysis of past and current trends of agrochemicals and cropping patterns within Canada indicates a rapid and systemic increase in chemical use, and policies that promote a shift toward lower chemical reliance through sustainable agricultural practices are urgently needed.
Part-per-trillion LC-MS/MS determination of neonicotinoids in small volumes of songbird plasma
(Elsevier, 12/10/2018) Hao, Chunyan; Eng, Margaret; Morrissey, Christy; Sun, Fengrong
Neonicotinoids are the most widely used class of insecticides in the world, and there are increasing concerns about their effects on non-target organisms. Analytical methods to diagnose exposure to neonicotinoids in wildlife are still very limited, particularly for small animals such as songbirds. Blood can be used as a non-lethal sampling matrix, but the sample volume is limited by body size. Neonicotinoids have a low bioaccumulation potential and are rapidly metabolized, therefore, sensitive assays are critically needed to reliably detect their residues in blood samples. We developed an efficient LC-MS/MS method at a part-per-trillion (pg/ml) level to measure eight neonicotinoid related insecticides (acetamiprid, clothianidin, dinotefuran, flonicamid, imidacloprid, nitenpyram, thiacloprid and thiamethoxam) plus one metabolite (6-chloronicotinic acid) in small volumes (50 μL) of avian plasma. The average recovery of target compounds ranged from 95.7 to 101.3%, and relative standard deviations were between 0.82 and 2.13%. We applied the method to screen blood samples from 36 seed-eating songbirds (white-crowned sparrows; Zonotrichia leucophrys) at capture, and detected imidacloprid in 78% (28 of 36), thiamethoxam in 22% (8 of 36), thiacloprid in 11% (4 of 36), and acetamiprid in 11% (4 of 36) of wild-caught sparrows. 6 h after capture, birds were orally dosed with 0 (control), 1.2 or 3.9 mg of imidacloprid/kg bw, test results using this method indicated that plasma imidacloprid was significantly elevated (low 26-times, high 316-times) in exposed groups. This is the first study to confirm neonicotinoid exposure in small free-living songbirds through non-lethal blood sampling, and to demonstrate that environmentally realistic doses significantly elevate circulating imidacloprid concentrations. This sensitive method could be applied to characterize exposure to neonicotinoids in free-living wildlife and in toxicological studies.
A neonicotinoid insecticide reduces fueling and delays migration in songbirds
(American Association for the Advancement of Science, 9/13/2019) Eng, Margaret; Stutchbury, Bridget; Morrissey, Christy
Neonicotinoids are neurotoxic insecticides widely used as seed treatments, but little is known of their effects on migrating birds that forage in agricultural areas. We tracked the migratory movements of imidacloprid-exposed songbirds at a landscape scale using a combination of experimental dosing and automated radio telemetry. Ingestion of field-realistic quantities of imidacloprid (1.2 or 3.9 milligrams per kilogram body mass) by white-crowned sparrows (Zonotrichia leucophrys) during migratory stopover caused a rapid reduction in food consumption, mass, and fat and significantly affected their probability of departure. Birds in the high-dose treatment stayed a median of 3.5 days longer at the site of capture after exposure as compared with controls, likely to regain fuel stores or recover from intoxication. Migration delays can carry over to affect survival and reproduction; thus, these results confirm a link between sublethal pesticide exposure and adverse outcomes for migratory bird populations.

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