Search for: All records

Technological advancements now enable the use of flow-through respirometry for rapid, high-throughput metabolic phenotyping, though live-in systems currently do not exist for birds. We designed live-in respirometry chambers for small birds with an Arduino-based electronic system to continuously monitor bird body weight, food intake, and water intake in sync with metabolic data collection. To demonstrate how this system can be implemented, we kept birds in the metabolic phenotypic chambers for 10 days while we progressively lowered the temperature from 25 °C to 5 °C. We used the data to calculate hourly energy expenditure and food/water intake during acute cold acclimation. We provide all plans and code for the live-in chambers, Arduino biomonitoring system, and additional RFID module as a low-cost, DIY alternative to commercially available systems and to enable the use of standard respirometry equipment for metabolic phenotyping in birds. 

Synopsis Endothermic species have evolved strategies to maximize survival in highly variable or extreme environments. Birds are exemplary as they are among the most widely distributed endotherms on the planet, living in all manner of inhospitable environments. As an example, winter in temperate regions is characterized by cold temperatures and low food availability. Some birds have evolved to tolerate these conditions by seasonally increasing thermogenic capacity, increasing heterothermy, and displaying highly flexible phenotypes. Other species have evolved to avoid the inhospitable conditions of winter altogether by migrating—again requiring a unique set of physiological adaptations that allow success in this challenging endeavor. In these examples and in many others, the organismal requirements for success share similarities, but the underlying mechanisms, physiological requirements, and selection on those traits can differ significantly, as can their ecological and evolutionary impacts. In recent years, a suite of novel and established tools has become widely available and more accessible, allowing insights into long-standing questions. Genomic tools, new approaches to measure organismal performance, the use of citizen science data, easier access to metabolite assays or hormone detection, to name a few, have spurred rapid advances in our understanding of avian physiology. These new tools have been leveraged to investigate important questions regarding avian responses to our rapidly changing climate in an attempt to understand species resilience and limits. 

Many bird species commonly aggregate in flocks for reasons ranging from predator defense to navigation. Available evidence suggests that certain types of flocks—the V and echelon formations of large birds—may provide a benefit that reduces the aerodynamic cost of flight, whereas cluster flocks typical of smaller birds may increase flight costs. However, metabolic flight costs have not been directly measured in any of these group flight contexts [Zhang and Lauder,J. Exp. Biol.226, jeb245617 (2023)]. Here, we measured the energetic benefits of flight in small groups of two or three birds and the requirements for realizing those benefits, using metabolic energy expenditure and flight position measurements from European Starlings flying in a wind tunnel. The starlings continuously varied their relative position during flights but adopted a V formation motif on average, with a modal spanwise and streamwise spacing of [0.81, 0.91] wingspans. As measured via CO₂production, flight costs for follower birds were significantly reduced compared to their individual solo flight benchmarks. However, followers with more positional variability with respect to leaders did less well, even increasing their costs above solo flight. Thus, we directly demonstrate energetic costs and benefits for group flight followers in an experimental context amenable to further investigation of the underlying aerodynamics, wake interactions, and bird characteristics that produce these metabolic effects.