Interpopulation differences and temporal synchrony in rates of adult survival between two seabird colonies that differ in population size and distance to foraging grounds

Understanding the processes that drive interpopulation differences in demography and population dynamics is central to metapopulation ecology. In colonial species, populations are limited by local resource availability. However, individuals from larger colonies will travel greater distances to overcome density-dependent competition. Consequently, these individuals may also experience greater carry-over effects and interpopulation differences in demography. To test this prediction, we use mark-recapture data collected over four decades from two breeding colonies of a seabird, the Manx shearwater (Puffinus puffinus), that exhibit strong spatial overlap throughout the annual cycle but differ in population size and maximum foraging distances. We quantify interpopulation differences and synchrony in rates of survival and assess whether local mean wind speeds act to strengthen or disrupt synchrony. In addition, we examine whether the imputed interpopulation differences in survival can generate population-level consequences. The colony where individuals travel further during the breeding season had slightly lower and more variable rates of survival, indicative of individuals experiencing greater carry-over effects. Fluctuations in survival were highly synchronous between the colonies, but neither synchronous, nor asynchronous, variation could be strongly attributed to fluctuations in local mean wind speeds. Finally, we demonstrate that the imputed interpopulation differences in rates of survival could lead to considerable differences in population growth. We hypothesise that the observed interpopulation differences in rates of adult survival reflect carry-over effects associated with foraging distances during the breeding season. More broadly, our results highlight that breeding season processes can be important for understanding interpopulation differences in the demographic rates and population dynamics of long-lived species, such as seabirds.

Unravelling the relative roles of top-down and bottom-up forces driving population change in an oceanic predator

In the open ocean ecosystem, climate and anthropogenic changes have driven biological change at both ends of the food chain. Understanding how the population dynamics of pelagic predators are simultaneously influenced by nutrient‐driven processes acting from the “bottom‐up” and predator‐driven processes acting from the “top‐down” is therefore considered an urgent task. Using a state‐space demographic model, we evaluated the population trajectory of an oceanic predator, the Macaroni Penguin (Eudyptes chrysolophus), and numerically assessed the relative importance of bottom‐up and top‐down drivers acting through different demographic rates. The population trajectory was considerably more sensitive to changes in top‐down control of survival compared to bottom‐up control of survival or productivity. This study integrates a unique set of demographic and covariate data and highlights the benefits of using a single estimation framework to examine the links between covariates, demographic rates and population dynamics.

Acute effect of consumption/omission of breakfast on exercise tolerance in adolescents

The purpose of this study was to determine the acute effects of the consumption or omission of breakfast on exercise tolerance in adolescents. Physically active adolescents (14 males and 21 females) were randomly assigned to receive a breakfast (B) or placebo (P) after an overnight fast. Exercise tolerance tests were done 1.5 hours (test 1) and again 4 hours (test 2) after consuming B or P and consisted of cycling on a stationary bike for 4 minutes at each of four consecutive power settings: 25, 50, 75, and 100 watts. Blood glucose and beta-hydroxybutyrate concentrations were measured before both tests. VO2 and VCO2 were measured during minute 3 of cycling at loads 50 and 75 watts and were used to compute the respiratory exchange ratio (RER). Heart rates (HR) were monitored throughout the test and ratings of perceived exertion (RPE) were made at the end of each 4 min interval. Repeated measures ANOVA revealed that there were no differences in RPE; however, differences for HR and RER did exist. Mean RER values were higher for the males receiving B vs males receiving P during test 1. For females, HR were higher for P compared B, and beta-hydroxybutyrate was significantly elevated for P before test 2. The data suggest that exercise tolerance as indicated by the ratings of perceived exertion are unaffected by prior ingestion of a breakfast but breakfast does affect the physiologic responses to exercise.

Leg power characteristics of female firefighter applicants

The primary purposes of this study were to characterize the anaerobic power of a large group of adult female subjects and to analyze the relationship of body composition, leg power, and leg strength tests to performance on the Wingate Anaerobic Test (WAT) in these women. A secondary purpose was to observe the relationship of the WAT to a stair-climbing test used to select firefighters. The subjects were the top 150 of the 1,090 women who took a firefighter applicant physical performance test. Predicted dependent variables from the WAT were mean power (MP), peak power (PP), and percent fatigue (%F). Among the nine independent variables entered into multiple regression analysis (age, height, weight, fat-free weight, percent fat, leg press strength, vertical jump, maximal physical work capacity (PWCmax) and stair climb) 45%, 40%, and 16% of the variance in MP, PP, and %F were accounted for. Fat-free weight accounted for the most variation in MP and PP, and PWCmax accounted for the most variation in %F. There was little relationship observed between MP, PP, or %F and the stair-climbing test.