The effect of sunrise timing and mountain aspect on the dawn chorus of Swainson’s Thrush


  • Ramnik Aojula University of Alberta
  • Anna Jacobsen University of Alberta
  • Erin Bayne University of Alberta



Swainson's Thrush, Catharus ustulatus, Mountain Aspect, Direction, Time Since Sunrise, Dawn Chorus


This study centers on the Swainson’s Thrush (Catharus ustulatus), uniquely identified by a buffy eye ring, uniformly brown back and tail, and a distinctive flute-like song with an ascending pitch. With a prevalent presence in woodlots, parks, and fruiting trees, they breed in coniferous forests with dense undergrowth, displaying notable vocalization and behaviour patterns. This research aims to explore the impact of pre- and post-sunrise timing and mountain aspect (North, East, South, West) on the dawn chorus of Swainson’s Thrush. The hypothesis posits that those exposed to earlier sunlight will sing prior to those experiencing delayed sunlight. Specific predictions are made for each mountain aspect, considering temperature, sunlight exposure, and resulting bird activity levels. To test the hypothesis, five audio recording units (ARUs) are set up across the mountain's four sides. Three recordings are made before and after sunrise for each side, grouped as North, South, East, and West. Results reveal a statistically significant interaction between direction and time since sunrise, while direction alone does not significantly impact song frequency. Time since sunrise and Julian's days also influence singing behaviour. The study shows the intricate relationship between environmental factors, sunrise timing, and mountain aspect on the dawn chorus behaviour of Swainson's Thrushes. These findings underscore the need for further investigation into additional factors influencing the dawn chorus, contributing to avian ecology and conservation understanding. By unravelling these complexities, conservation efforts can be better informed and aligned.


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Bégin-Marchand, C., Desrochers, A., Taylor, P.D., Tremblay, J.A., Berrigan, L., Frei, B., Morales, A., Mitchell, G.W. (2021). Spatial structure in migration routes maintained despite regional convergence among eastern populations of Swainson’s Thrushes. Movement Ecology. 9(1): 1-11.

Britannica, T. Editors of Encyclopaedia. (2017). Waterton Lakes National Park. Encyclopedia Britannica.

Cassone, V.M. (2014). Avian circadian organization: A chorus of clocks. Frontiers in Neuroendocrinology. 35(1):76–88.

Da Silva, A., & Kempenaers, B. (2017). Singing from North to South: Latitudinal variation in timing of dawn singing under natural and artificial light conditions. The Journal of animal ecology, 86(6), 1286–1297.

Farina, A., Ceraulo, M., Bobryk, C., Pieretti, N., Quinci, E., Lattanzi, E. (2015). Spatial and temporal variation of bird dawn chorus and successive acoustic morning activity in a Mediterranean landscape. Bioacoustics, 24(3):269–288.

Greenberg, S., Godin, T., & Whittington, J. (2019). Design patterns for wildlife‐related camera trap image analysis. Ecology and Evolution, 9(24), 13706-13730.

Henderson, C.R. (1977). Best Linear Unbiased Prediction of Breeding Values Not in the Model for Records. Journal of Dairy Science, 60(5):783–787.

Hrach, D.M., Petrone, R.M., Van Huizen, B., Green, A., Khomik, M. (2021). The Impact of Variable Horizon Shade on the Growing Season Energy Budget of a Subalpine Headwater Wetland. Atmosphere , 12(11): 1473.

Mack, D.E., Yong, W. (2020). Swainson’s Thrush (Catharus ustulatus). Birds of the World.

Maphisa, D. H., Smit-Robinson, H., Underhill, L. G., & Altwegg, R. (2016). Drivers of Bird Species Richness within Moist High-Altitude Grasslands in Eastern South Africa. PloS one, 11(10), e0162609.

McLean, N., van der Jeugd, H. P., & van de Pol, M. (2018). High intra-specific variation in avian body condition responses to climate limits generalisation across species. PloS one, 13(2), e0192401.

Naguib, M., Diehl, J., van Oers, K., & Snijders, L. (2019). Repeatability of signalling traits in the avian dawn chorus. Frontiers in zoology, 16, 27.

Pérez-Granados, C., Osiejuk, T. S., & López-Iborra, G. M. (2018). Dawn chorus interpretation differs when using songs or calls: the Dupont's Lark Chersophilus duponti case. PeerJ, 6, e5241.

Ross, G. J. S., & Preece, D. A. (1985). The Negative Binomial Distribution. Journal of the Royal Statistical Society. Series D (The Statistician), 34(3), 323–335.

RStudio Team. (2020). RStudio: Integrated Development for R. RStudio, PBC, Boston, MA.

Shonfield, J., Bayne, E.M. (2017). Autonomous recording units in avian ecological research: current use and future applications. Avian Conservation and Ecology. 12(1): 1-14.

Smith, J. M., & Harper, D. D. (2003). Animal Signals. In Google Books. OUP Oxford. zPGpkzVqs3&sig=psBC9fX2BZSbdriMDLArZoJFC2k&redir_esc=y#v=onepage&q&f= false.

Vuong, Q. H. (1989). Likelihood Ratio Tests for Model Selection and Non-Nested Hypotheses. Econometrica, 57(2), 307–333.

Yang, J., El-Kassaby, Y. A., & Guan, W. (2020). The effect of slope aspect on vegetation attributes in a mountainous dry valley, Southwest China. Scientific reports, 10(1), 16465.

Yip, D.A., Mahon, C.L., MacPhail, A.G., Bayne, E.M. (2021). Automated classification of avian vocal activity using acoustic indices in regional and heterogeneous datasets. Methods in Ecology and Evolution, 12(4):707–719.




How to Cite

Aojula, R., Jacobsen, A., & Bayne, E. (2023). The effect of sunrise timing and mountain aspect on the dawn chorus of Swainson’s Thrush. Eureka, 8(2).