Dominance and Aggression Among Hummingbirds of the Cloud Forests of the Talamanca Mountains, Costa Rica Claire Nickles, Crystal Sauder, and Aileen Scarim1 1 Student, Dept. Biological Sciences, Olivet Nazarene University, Bourbonnais, IL Costa Rica is home to 48 different species of hummingbirds, with eight species being located in the Savegre Valley of the Talamanca Mountains.1 Some of the species in the Talamanca Mountains are endemic to that region only. Hummingbirds have small bodies, long beaks, long translucent tongue, and fast movement of their wings. All of those qualities help hummingbirds fill niches in the environment that would be empty without them. Males tend to claim around a quarter of an acre, where as the females will stay closer to their nests.3 Males also defend the resources that are in their territories. To our knowledge, little is known about interactions between these species. The dominance and aggression that was exhibited in the cloud forests of the Talamanca Mountains could end up changing the in the future. As the climate changes, different species are expanding their habitat range and can cause more species to interact with one another. Introduction Implications Endemic Talamanca hummingbirds were more aggressive than the nonendemic species, while the endemic volcano hummingbird was the most submissive. (Figures 1 and 2). Talamanca hummingbirds (E. spectabilis) are the largest in size compared to the four other species.1 Having the size advantage may be an advantage to defend the feeder from other individuals. One male guarded the feeder from all the other hummingbirds. Two of the three main males were endemic species, which supports our data showing the endemic species were more aggressive. Results: Behavior based on sex The endemic Talamanca males have a higher percentage of aggressive behavior The endemic Talamanca females have a higher percentage of aggressive behavior Research Question Will the males of different hummingbird species be more aggressive at hummingbird feeders over females? Figure 1. The percentage of interactions when a male hummingbird was either aggressive or submissive. The chaser was the aggressive individual, with the one being chased as the submissive individual. Each interaction between hummingbirds were recorded individually. The percentage of those chasing versus those being chased was totaled. Figure 2. The percentage of interactions when a female hummingbird was either aggressive or submissive. The chaser was the aggressive individual, with the one being chased as the submissive individual. Each interaction between hummingbirds were recorded individually. The percentage of those chasing versus those being chased was totaled. Results: Behavior based on species Methods Our research took place in the Savegre Valley in Costa Rica on 23 May, 2018. Three different feeding locations around the valley were used for observations. Each member of the group made observations from one of the locations resulting in a total of six hours at each location, three in the morning and three in the afternoon, combined to 18 hours of observations total. Sex and species of each bird was documented. The behavior demonstrated from each bird was noted by a series of symbols. All behaviors were categorized into the following: drinking, chasing, being chased, leaving the feeder on their own, and perching on the feeder were assigned. The endemic Talamanca hummingbirds (E. spectabilis) were the most aggressive out of the five species observed, no matter the sex. Contact Information Claire Nickles: cnickles@olivet.edu Crystal Sauder: crsauder@olivet.edu Aileen Scarim: arscarim@olivet.edu Figure 3. The total percentage of interactions for each species. Male and female percentages were combined to get the percent interactions total for the species as a whole. References 1Garrigues, R., & Dean, R. (2014). Birds of Costa Rica: A field guide (2nd ed.). London: Chri 2Hobbs, M. and T. S. Schulenberg (2017). Lesser Violetear (Colibri cyanotus), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/nb.lesvio1.01 3Hummingbird Behaviors. (n.d.). Retrieved July 30, 2018, from http://www.hummingbirdsplus.org/facts/behaviors/#