Date of this Version
Oden, Amy I. 2013. Changes in avian vocalization occurrence and frequency range during the winter. MS thesis. University of Nebraska.
Human population expansion has led to an increase in vehicle traffic and therefore vehicle noise. Traffic and traffic noise has been shown to affect avian abundance, breeding success, density and species diversity on the landscape. Documented changes in avian vocalizations due to traffic noise include shifts in amplitude, frequency, rate, timing, and duration of vocalizations along with a number of behavioral adaptations. During the winters of 2011–2012 and 2012–2013, we recorded and measured the “chick-a-dee” vocalization of Black-capped Chickadees (Poecile atricapillus) and the “po-ta-to-chip” vocalization of American Goldfinches (Spinus tristis) to determine if bird vocalizations near high traffic noise had higher minimum and maximum frequencies than bird vocalizations near low traffic noise. We found that both the Black-capped Chickadee and American Goldfinch vocalizations have a higher minimum frequency near high traffic noise while the maximum frequency showed no change. This suggests that these species will alter the part of their vocalization that is acoustically masked by traffic noise in order to better transmit the vocalization. However, costs of altering vocalizations include the inability to attract a mate, poor vocal performance, not sounding like conspecifics, and being more easily heard by predators. Chickadees also alter how often they vocalize based on their flock composition. Chickadees vocalize more in mixed-species flocks with other satellite members than in flocks that contained juncos or in single-species flocks of chickadees. Also, single species flocks of Black-capped Chickadees tended to be smaller in size and mixed-species flocks of Dark-eyed Juncos plus individual satellite members tended to be larger in size.