All About the American Redstart: Setophaga ruticilla
General
American Redstarts start singing formless songs after 2-3 weeks of being born and acquire adult songs after about 5 months (Sherry et at., 2016). During the breeding season, male American Redstarts usually sing a series of 2-11 notes. These are thin, high-pitched notes, occasionally ending in accented phrases. Because the notes build in energy and end with the accented note, they are often described as being sneeze-like. Along with songs, males and females both use calls to communicate. Calls are used in a social context, which can include foraging, anti-predator behavior, or parent to offspring interactions. These calls include sharp chip notes, softer tsip calls, and higher-pitched alarm calls. Along with songs and calls, males make snapping sounds with their bills at other males as a way of protecting their territory, and females sometimes will do the same at males while they are courting (“American Redstart”).
Interestingly, calls amongst different closely related species of wood-warblers vary in characteristics. American Redstarts calls are similar to the others in their ‘check-mark’ shape. However, unlike similar birds their flight call has been shown to have a longer downward slope (Keen et al., 2014). The American Redstarts are highly territorial birds and use song as a way to defend their territories. The territory that male birds aquire is maintained during the breeding season while the male defends the area against other males (Ickes and Ficken, 1970).
Figure 1 below shows sonograms of different American Redstart’s vocalizations. Sonograms A and B show songs with accented endings. While C-F should un-accented ending songs.
Figure 1: Sonograms of American Redstart Vocalizations
What is functional classification of songs and how does it relate to the existence of dialects in the American Redstart?
In addition to being classified as passerines, American Redstarts are also classified as paruline warblers. Like other species within this classification, American Redstarts repertoires are divided into functional subsets. These functional subsets include ‘repeat’ and ‘serial’ songs. Repeat and serial songs are different in both presumed function and song characteristics. The singing of repeat songs is characterized by the repetition of one song which has an accented ending. On the other hand, the singing of serial songs is characterized by the random singing of different songs which are unaccented (Morse, 1966).
Figure 2 below provides a visual of the differences in accented and unaccented ending songs as shown by a sonogram of a very closely related bird to the American Redstart. The top shows an accented-ending song, while the bottom shows an unaccented-ending song.
Figure 3: Accented vs. Unaccented Yellow Warbler Song
These types of songs also differ in the behavioral context in which they are sung. While serial songs are primarily sung in male-male interactions, repeat songs occur most often early in the breeding season, indicating that they may have a relative importance in breeding behavior. In addition to having different functions, repeat songs and serial songs have varying levels of importance within the birds repertoire. While repeat songs are oftentimes kept constant throughout a Redstart’s life, serial songs have been shown to change throughout their lifetime. These changes in serial song are oftentimes attributable to a male’s proximity to another adult male, as males may acquire the serial songs of their neighbors. Research done indicates that the the songs which were retained from year-to-year within Redstarts’ repertoires were the ones which were shared with a neighbor. This points to the creation of neighborhoods of song/different dialects (Lemon et al., 1992).
Figure 3: Singing Video of ‘American Redstart in Maine’
What are the potential functions of (nocturnal) flight calls and how are they related to current research?
As discussed earlier, a type of vocalization which is commonly utilized by American Redstarts are flight calls. Flight calls, also referred to in a recent study as nocturnal flight calls, are commonly single-syllabled vocalizations which serve various functions within flocks. Recent research by Griffiths et al. (2016) has attempted to look into the potential transferring of specific identifying information through the use of flight calls, specifically nocturnal flight calls. The researchers predicted that flight calls could be related to the transference of information between individuals of different sexes and flocks as a whole. In the study, the acoustic features and similarity of flight calls between different groups (sexes, individuals, and age groups) was examined. The results indicated that the least variation in flight calls was within the recorded calls of a single individual, while there were greater differences between sexes. There were some differences between the calls of different age groups of the same sex, but the researchers indicated that these were negligible and consequently concluded that it is unlikely that flight calls change drastically over a bird’s lifetime. The greater implications of this study point to the possible transference of gender specific and individual related information through the usage of flight calls.
A major point which was discussed in the aforementioned study, was the potential importance of the ability to transfer information through flight calls during nocturnal migration. Griffiths et al. (2016) explain that if flight calls are in fact able to transfer individual-specific information, they could play an important role in nocturnal migration as at nighttime visual cues prove to be ineffective.
Additionally, this research and discovery is interesting in context of the study of American Redstart’s repertoire and song learning behavior. While Redstarts are characteristically known to change their ‘serial’ songs from year-to-year depending on the location of their territory and their neighbors (dialects), calls appear to be a unchanged and fundamental part of interpersonal interactions within the species.
More research is being conducted on this and should continue to provide interesting insights into the function of calls within the American Redstart species (Griffiths et al., 2016).
Figure 4: Cute picture of male and female American Redstart…enjoy!
Citations:
“American Redstart .” All About Birds, Cornell Lab of Ornithology Online. Accessed: April 23, 2018. www.allaboutbirds.org/guide/American_Redstart/id
Griffiths, E.T., Keen S.C., Lanzone M., and Farnsworth, A. 2016. Can nocturnal flight calls of the migrating songbird, American Redstart, encode sexual dimorphism and individual identity? PLOS ONE 11.
Ickes, R.A. and Ficken, M.S. 1970. An investigation of territorial behavior in the American Redstart utilizing recorded songs. The Wilson Bulletin 2: 167-176.
Keen, S., Ross, J.C., Griffiths, E.T., Lanzone, M., Farnsworth, A. 2014. A comparison of similarity-based approaches in the classification of flight calls of four species of Both American wood-warblers (Parulidae). Ecological Informatics 25-33.
Lemon, R.E., Perreault, S., Weary, D.W. 1994. Dual strategies of song development in American Redstarts, Setophaga reuticilla. Animal Behavior 47: 317-329.
Sherry, T.W., Holmes R.T, Pyle P., and Patten M.A. 2016. American redstart. Birds of North America Online.
Morse, D.H. 1966. The context of songs in the yellow warbler. The Wilson Bulletin 4: 444-455.
Figure Citations:
Figure 1: Sherry, T.W., Holmes R.T, Pyle P., and Patten M.A. 2016. American redstart. Birds of North America Online. Accessed: April 27, 2018.
Figure 2: Morse, D.H. 1966. The context of songs in the yellow warbler. The Wilson Bulletin 4: 444-455. Accessed: April 27, 2018.
Figure 3: Wild Bird and Nature Videos McElroy Productions. Adult American in Maine. May 24, 2012. Youtube. Accessed: April 27, 2018. https://www.youtube.com/watch?v=MDQWIkKK_ng&feature=youtu.be. Accessed: April 27, 2018.
Figure 4: Unknown photographer. 2011. Photo of ‘An ASY male and female American Redstarts.’ Powdermill Nature Reserve: Avian Research Center. https://powdermillarc.org/pictorial-highlights/late-spring-2011/. Accessed: April 27, 2018.
