Stress & Survival: Birds Hanging in the Balance

As university students, we spend plenty of time trying to manage our stress levels when dealing with a plethora of assignments, projects, and exams. Stress has proven to affect the academic performance of students, but did you know that it may be the key to survival for birds in ever changing climactic conditions?

Biologist Roslyn Dakin and a team of researchers recently published a study with one goal in mind – to determine how stress affects the survival of baby tree swallows.

 In order to manipulate the stress levels of the swallows, Dakin implanted corticosterone pellets into their bloodstream. Corticosterone, a stress hormone, has been shown to impact how often a mother would feed their offspring. Therefore, experimenting with its levels should affect survival.

So what exactly did Dakin find? Their results were seriously disturbed by exceptionally cold and wet weather, the ramifications of which are discussed in the podcast below:

The study revealed some extremely complex relationships between stress, weather, parental investment, and ultimately, survival. An increase in corticosterone did not necessarily lead to an decrease in mortality, as predicted. In fact, the offspring of mothers with higher corticosterone levels showed an increased risk of failure. In inclement weather, however, all individuals had a high likelihood of mortality.

One fascinating finding involved the relationship between the male and female parents. As expected, with  high female feeding rates, the offspring were more likely to survive. However, high male feeding rates combined with corticosterone-implanted females resulted in a higher risk of failure compared to females without the implants. Why is this the case? Wouldn’t more care from a parent allow for better survival? Several hypotheses were proposed. Highly invested males may be more sensitive to changes in their partner. As well, the female may be more likely to abandon their offspring if they feel that the male could care for the offspring on their own.

More questions were raised than answered in the study, and unfortunately swallow populations continue to dwindle in Ontario, where the experiment took place. Clearly, any solution proposed will have a variety of factors at play. Nonetheless, we valiantly attempted to tackle the issue of declining bird populations in unpredictable weather – check out our video below for more!

Tim Cheung, Peggy Hung, Kamyar Kazemiashtiani, & Josephina Kim