Saddleback Journal of Biology - Saddleback College

Spring 2010 Biology 3B Paper
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Time of Day Effects on The American Crow’s Assembly Call (Corvus americanus)
Sherwin Jenabian
Department of Biological Sciences
Saddleback College
Mission Viejo, California 92692
Corvus americanus is found throughout the United States and its vocal behavior has
interested ornithologists for many years. The crow’s superior intellect has led to the
development of a complex communication system which consists of a definite set of diverse
sounds, each of which occurs in a particular situation and seems to have a predictable
effect upon the behavior of other crows. In this study the assembly call of the American
Crow was replicated and examined what effect the time of day had on the number of birds
that responded to the call. The assembly calls were recorded and played them back during
the weekends on the Saddleback College campus between March 27 th 2010 and April 10 th
2010. The calls were played in 2 minute intervals, 9 times in the morning right after sunrise
on 5 separate days (n=45), and 9 times towards the end of the day right before sunset on 5
separate days (n=45). Crows responded by flying over the source of the call in both cases,
but the calls played at dusk attracted a greater number of crows compared to that of the
morning. Results determined a significant difference in the number of crows that
responded to an assembly call between the morning and late afternoon, thus rejecting the
null hypothesis.
Introduction
Interest in the common American Crow
(Corvus americanus) has increased in the past decade
among ornithologists due to its superior intellectual
properties. Crows have been known to live in
complex social groups and have been documented to
have many of the same intellectual characteristics as
primates. When it comes to brain to body-mass ratio,
the corvid brain is among the largest in birds and
almost equal to that of apes. Some speculate that this
has helped them develop a very complex
communication system. This system has been built
around a set of different tones, and depending on the
intended message being conveyed, other crows
respond in the same manner. Even the casual
observer of crow behavior can detect changes in pitch
and rate of call delivery, an indication of the
communicative potential and behavioral complexity
of crow vocalizations (Johnston, 1961).
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Saddleback Journal of Biology
Spring 2010