How to adapt your birdly behavior to the river flow?by Mireia Kohler Pacino and Oihana Olhasque
Published by the May 4, 2020 on 2:05 PM
The natural flow regime paradigm and the aim of study
In 1997, the natural flow regime paradigm has been established. This paradigm has become a real basement of management and basic biological study of running water ecosystems (Poff et al., 1997). This one establishes that the temporal variation in river flows requires the adaptation of structure and function of the aquatic ecosystems. To better understand this adaptation, many animals have been studied. In our case, the Cinclus Cinclus is chosen because of his large distribution in the world. We want to figure out if his behavior and energy use strategies are dictated by the natural river flow. We’ll use time-activity and time–energy budgets. In fact, it has proved to be a convenient approach to assess a bird's use of time and energy expenditure.
Using time-activity budget
Different behaviors of dippers
To answer to this question, the time-activity budget of the White-throated Dipper (Cinclus cinclus) was studied within a water basin in the Pyrenees, where natural flow regime is highly seasonal. To study the time activity budget, bird activities were categorized under four main headings: resting, foraging, diving and flying. In the study, between October 1998 and August 2001, birds activities were monitored each month using a portable tape recorder in combination with a telescope at a distance of 30–100 m. Overall, the analysis was made on 130 recordings: 62 males, 52 females, and 16 birds of unknown sex. As strategies could depend on external and river conditions, air temperature, water temperature and water column depth were measured on the behavioral surveys.
Parameters used in the study
Authors assumed that the Daily Energy Expenditure is calculated from an equation that includes time-energy budgets (obtained by incorporating time activity data), basal rate of metabolism, thermoregulation, locomotion, foraging, digestion, growth, reproduction, as well as all energy expenditures that eventually end up as heat production. The required foraging rate and the observed rate of energy gain were also calculated by dividing Daily Energy Expenditure with, respectively, the active day length for birds and the total time spent feeding by birds. Consequently, the ratio “Observed rate of energy gain” / “Required foraging rate” indicates how much faster observed feeding rates are in relation to minimum required feeding rates. For example, if birds gather food at a rate just enough to balance their energy budget then this ratio is equal to 1.
Parameters used in the DEE equation
Results synthesis
The natural river flow is high during snowmelt (between April and June) and very low in summer. The behaviors are also chasing due to season: In winter our birds spend more time in foraging where food is rarely found and the water flow didn’t increase. In May, went the river flow increase, they have a rest for 70% of the day. Diving, flying and other activities showed no peculiar pattern, but there’s a relationship between water stage and time spent diving. Moreover, the ratios, observed rate of energy gain / required foraging rate indicated our birds could face high energy stress during winter but paradoxically none during high snowmelt spates when food is expected to be difficult to obtain. Unfortunately, the daily energy expenditure doesn’t seem to show any annual pattern. At this step of the study, they couldn’t find out whether Dippers use an energy strategy.
To go further....
With the actuals methods like calorimetry will be a complement to this study. To figure out, more information about dippers cycle life and potentials energy strategies. More generally, this study will serve the overwhelming challenge of maintaining native birds (especially those at risk) and more generally speaking biodiversity in human-altered rivers and streams.
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