April 20, 2015
Thank you Sophie Ruff, guest student blogger, for taking the time to teach us a little bit about dominance interactions between different species of chickadees. Who knew that 12 grams could be so tough!
When you think about dominance in animals, large carnivores like lions, tigers, and bears probably come to mind. But if you take a look at your backyard bird feeder, you may see a surprising alpha-species hopping about in search of their favorite sunflower seeds. That’s right: a recent study by researchers at the University of Northern British Columbia and the University of Lethbridge in Alberta provides a variety of evidence for the dominance of the 12 gram fluff ball we know as the Black-capped Chickadee.
Occupying the deciduous forests of North America and known for its complex songs, the Black-capped Chickadee is a common feeder bird throughout the northeast United States. However, its relative, the Mountain Chickadee, prefers coniferous forests, which usually means that it does not come into contact with the Black-capped Chickadee. However, recently, lumbering patterns in Northwest Canada have created regions of deciduous and coniferous forest patches. This creates an environment for the interaction of the two chickadees.
When the Canadian research team looked at how those two species interacted, the Black-capped Chickadees was dominant regardless of the method used to examine their interactions. First, chickadees were caught and tagged with indicators of their species, sex, and age. The two can be hard to distinguish in the field, and so this let the scientists know exactly who they were observing. Then, when the researchers watched the birds interact at feeders, 159 of the 190 interactions showed Black-capped Chickadees as the dominant species. The researchers also caught some birds and brought them into an aviary for more careful observation. But the results were the same – in this case, 81 of the 82 interactions had Black-capped Chickadees as the winners.
In addition to looking at the behavioral trends, the researchers took their work a step further. Genetic analyses show that the Black-capped Chickadees and Mountain Chickadees actually hybridize and create offspring of mixed genetic background. However, the hybrid nestlings were only ever found in Mountain Chickadee nests – never in Black-capped Chickadee nests. The implication? While a Mountain Chickadee female will happily mate with a dominant Black-capped Male, the Black-capped females will not let the Mountain Chickadee males anywhere near them. As with many other animals, the facts imply that in chickadees more dominant males have the most mating success.
Grava, A., T. Grava, R. Didier, L. A. Lait, J. Dosso, E. Koran, T. M. Burg, and K. A. Otter. “Interspecific Dominance Relationships and Hybridization between Black-capped and Mountain Chickadees.” Behavioral Ecology 23.3 (2012): 566-72.