Why Do Blue Jays Call Before It Rains
Blue Jays are often considered to be among the most intelligent birds. This makes them both very interesting and hard to capture and study (Kroodsma, 2005). Not much work has been done on the vocalizations of Blue Jays and most of the research that has been done is unpublished work by graduate students. What we do know about their vocalizations, however, is very interesting. Blue Jays are songbirds by bloodline, and closely related to many birds with many very complex songs. However, they do not sing, but instead rely on calls to communicate (Kroodsma, 2005). Even though they do not sing, Blue Jays have an immense vocabulary that makes a categorization of their calls difficult. Their calls can be sorted into four categories that are based on frequency range, tonal quality, harmonics and function. These categories are jeer calls, pumphandle calls, intrapair contact calls, rattle calls and a fifth category that includes any other calls that don't fit in the first four groups. Many of these calls are used in multiple contexts and have many variations, making these categories hard to distinctively draw.
Jeer calls are used to assemble Jays, for mobbing and when the Jay feels threatened. Jeers are harsh, loud and non-musical calls that are nonetheless rich in harmonics All other aspects of these calls, such as frequency, inflection, tempo, and so on, vary from bird to bird and call to call. Pumphandle calls are musical and clear and sound like whistles. One form of these calls serves as an alarm for a low-intensity threat. When making intrapair contact calls, Blue Jays make low-volume guttural clicking noises.These are emitted while the paired Jays are performing activities such as nest-building or foraging, or when they are interacting with another pair. Begging calls, produced both by young offspring and by adult females, are an example of an interpair contact call. These calls vary based on the excitement level of the pair. Rattle calls are only emitted by females and are a series of rapid clicks that often have one sharp click at the beginning and end of the call. These are often emitted within a flock, as alert calls, or when another jay intrudes on a pair's space.
Blue Jay's acquire their entire vocal repertoire within 6 months from birth. Some calls are probably developed from cries, for example jeer calls and intrapair contact. These disappear from a Blue Jay's repertoire a few months after their postfledging period ends, but these calls reappear months later in a different context. Blue Jays learn most of their calls, especially the calls that belong to the Pumphandle group. There have been experiments that show that nestlings who are raised in isolation up to their 8th month of life will not develop a Squeaky-Gate Call, and the rest of their calls were fairly different from a Blue Jay's normal calls. On the other hand, a nestling that is raised exposed to recorded calls will develop calls that resemble the one of the model. For Blue Jays, an exact learning period has not been experimentally determined, although it is probable that Blue Jays are capable of learning new calls and modifying their old ones throughout the course of their lives.
The Blue Jay often modulates its repertoire calls in order to mimic the sounds of other birds. Some calls can be clearly traced down to the song they are mimicked from (Kroodsma, 2005). For example, imitations of Red-tailed and Red-shouldered hawks are modulations of jeer and pumphandle calls, and Cooper's Hawk and Eastern Screech-Owl calls are often modulations of intrapair contact calls. Blue Jays in captivity have even been able to imitate the sounds of American Crows, domestic felines, and some human sounds.
Birds who do not have a mate call more frequently than mated jays during pre-breeding season. This supports the idea that Blue Jays sing with the purpose of attracting a mate. The frequency with which Blue Jays sing certain calls depends on the season; some songs are more common during the period January to April than from May to June, which is the nesting period. This repertoire frequency is often reversed during these seasons and the songs who were not as common during January to April become frequently used from May to June. On the other hand, intrapair contact calls are common throughout the whole year. Blue Jays generally vocalize while perched in trees. Some calls, like jeer and intrapair contact calls, can be given in almost any position or situation, although rarely while foraging on the ground. Finally, pumphandle calls are generally given in flight during flocking of fall and spring.
The following diagrams are spectrograms of a variety of Blue Jay calls. Spectrograms show the frequency over time of the vocalizations made.
A) Ditonal Jeer Call. B) Monotonal Jeer Call. C) Squeaky-Gate Call. D) Bell Call. E) Kut Kuet Call. F) Rattle Call
(Source: http://bna.birds.cornell.edu/bna/species/469/galleries/figures/figure-3/image_popup_view)
Further research in this field might center on the evolutionary reasons why blue jays don't sing and when their last ancestor had song. This is an evolutionary question that could be answered with the help of phylogenies, which are diagrams that show evolutionary history of species. It would also be interesting to investigate the Blue Jay's propensity to mimic hawk cries – are they somehow physically predisposed to be especially good at mimicking hawk cries or is it just what calls they are exposed to that determines who they mimic? Playback experiments could be useful in determining whether Blue Jays are particularly likely to mimic hawk calls. Field studies will be useful in further determining which calls are used in which situations.
Bibliography
Goto, K. 2014. Visual search and attention in blue jays (Cyanocitta cristata): Associative cuing and sequential priming. Journal of Experimental Psychology. Animal Learning and Cognition 40: 185-194.
Kroodsma, D. 2005. Songbirds without a song In: Kroodsma, D. The Singing Life of Birds. Houghton Mifflin Company, New York, pp. 179-191.
Schaef, K.M. and Mumme, R.L. 2012. Predator vocalizations alter parental return time at nests of the hooded warbler. The Condor 114: 840-845.
Further references:
http://bna.birds.cornell.edu/bna/species/469/articles/sounds (Accessed May 2nd, 2015)
http://www.allaboutbirds.org/guide/Blue_Jay/sounds (Accessed May 2nd, 2015)
Source: https://pages.vassar.edu/sensoryecology/the-blue-jay-vocalizations/
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