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The Burrowing Owl, a Unique Bird of Prey

My Independent Study for Dr. G.L. Chew involved a closer look at the Burrowing Owl otherwise known as Speotyto cunicularia. I observed for a total of ten hours carefully watching the owls' behaviors while focusing on their different types of vocalizations. Each visit was an hour long and was divided into 15 minute intervals. This made it possible to lessen the chance of two potential interruptions. First, the possible chance of a thunder storm occurring during an observation, which had become a common threat. Second, the possibility that the owls may adapt to my presence thereby becoming less vocal and making it more difficult to collect data. The Canadian Burrowing Owl Recovery team (1995), supports this idea by claiming that the owls are quite adaptable to the presence of humans to the point where they have been found nesting in highly populated areas.

The subjects observed included three pairs of Burrowing Owls living comfortably in a cage approximately 40 feet long, 12 feet high, and 10 feet wide at The Alberta Birds of Prey Visitor Center located in Coaldale, Alberta. For purposes of recording data such as who vocalized at what time and what association was made, I labeled each owl either A, B, C, D, E, or F. In order to identify and keep track of each owl I payed close attention to their preferred location which was usually in proximity to their nest burrow. Each owl shares their nest burrow with their mate and their young when the time comes. Even though Burrowing Owls tend to allow their neighbors into their territory and under desperate conditions into their nest burrow, great precaution is taken. For example, neighbors are often aggressively confronted when they cross into another's territory. I also relied on slight differences in appearance such as size, color, difference in markings, and brightness of eyes. Although Burrowing Owls are classified as monomorphic, the females appeared to be slightly smaller than the males. I was able to draw this conclusion by associating the females with their duration of incubation compared to the males. According to Spofford (1983), both male and female incubate the eggs; however, I observed that the females (smaller in size) were the owls devoting more time to incubation which means they spent more time inside the nest cavity compared to the males in this particular study.

The following includes a complete overview of the data that I collected for a total of ten hours divided into 15 minute or 900 second intervals.

Observation 1

At 210 seconds, an extended pattern of calls (whee, chirp, chirp) were vocalized by Owl C. These vocalizations were lower pitched and the owl appeared to be calm leading me to believe that this was a chatter call (seemingly aimless sounds).

At 420 seconds, an extended pattern of chirping (many chirps) was vocalized by Owl C while scanning the environment. These vocalizations were higher pitched expressing a sense of urgency which gave me the impression that they were warning calls.

At 450 and 690 seconds, Owl C vocalized short, intermittent single chirps while bobbing its head seemingly directed towards its partner D. According to Spofford (1983), this is a sign of acknowledgment.

At 720 seconds, Owl D focused on the same object as its partner C while chirping an extended pattern of calls (many chirps). Owl D appeared to be agitated leading me to believe that these sounds represented a type of distress call that signaled a condition of danger to its partner.

Observation 2

At 240 seconds, Owl A chirped once while bobbing its head. The owl appeared to be acknowledging my presence since it was focused on me.

At 360 seconds, Owl C chirped once while bobbing its head. It seemed to be acknowledging Owl B's presence as it was facing in its direction.

At 380 seconds, Owl B squawked once while spreading its wings. This seemed to be a warning call directed towards Owl C since they were facing each other. The indication of it being a warning call was the owl's agitation, urgency and the harsh loud cry typical of a squawk.

Observation 3

At 460 seconds, short, intermittent single chirps were vocalized by Owl D apparently directed towards its partner C as they were facing each other. These short sharp sounds reflected distress and concern as Owl D scanned the environment.

At 470 seconds, Owl C shared the same distress and concern as it responded with short, intermittent single chirps while scanning the same area of interest.

At 640 seconds, Owl E vocalized a single chirp while bobbing its head then flew by Owl C and its partner D. Initially, Owl E was acknowledging the other owls and their territory before attempting to fly across this area of land.

At 650 seconds, as Owl E flew by, Owl C acknowledged its presence with a single chirp and a head bob.

Observation 4

At 220 seconds, Owl D acknowledged my presence by vocalizing a single chirp and bobbing its head while staring in my direction. It then flew to a perch near its partner C.

At 390 seconds, an extended pattern of calls (whee, chirp, chirp) were vocalized by Owl C apparently directed towards its partner D. Once again, these vocalizations

were lower pitched and the owl appeared calm supporting the idea of this being a social call.

At 610 seconds, Owl D vocalized short, intermittent single chirps while eating. The owl, fearing I might compete for its food source, felt threatened by my presence.

At 730 seconds, Owl D vocalized an extended pattern of calls (whee, chirp, chirp) while grooming its partner C. This pattern of sounds seemed to be a type of social communication since the owls were interacting in a relaxed manner.

Observation 5

At 420 seconds, Owl D chirped twice while flying over to Owl B's location. Owl D appeared agitated and concerned with my presence obviously representing another type of distress call.

At 450 seconds, Owl B responded to Owl D by vocalizing short, intermittent single chirps while focusing on my presence. Owl B also exhibited concern regarding my presence supporting the distress call theory.

Observation 6

At 360 seconds, Owl D vocalized a single chirp while facing its partner C. This could possibly be another form of acknowledgment.

At 370 seconds, Owl C responded with short, intermittent single chirps as it stared in my direction. It then groomed its partner D. Owl C appeared to be uncomfortable with my presence, but eventually carried on with its activities.

At 740 seconds, Owl E acknowledged my presence by vocalizing a single chirp and bobbing its head while staring in my direction.

Observation 7

At 180 seconds, Owl E vocalized a single chirp while focusing on Owl D. Once again I believe this to be a form of acknowledgment.

At 480 seconds, Owl D responded to Owl E by vocalizing an extended pattern of calls (whee, chirp, chirp). Once again, this appeared to be a social call directed towards another owl in a relaxed manner.

At 510 seconds, Owl E vocalized a "whee" sound as a way of continuing communication with Owl D. This also seemed to be a type of social call since the owls were interacting in a relaxed manner.

Observation 8

At 190 seconds, Owl F vocalized many chirps while staring at me seemingly directed towards its partner E. The Owls were in proximity to one another as both repeatedly glanced at me and then at each other in an uneasy manner. My interpretation was that this repeated sound represented a distress call with reference to my presence as it was a sharp noise most likely reflecting urgency.

At 520 seconds, a "whee" sound was vocalized by Owl B. This vocalization appeared to be a social call directed towards Owl C as they were facing each other and interacting in a relaxed manner.

Observation 9

At 380 seconds, Owl F squawked twice which seemed to be directed towards its partner E as they were facing each other. Apparently Owl F was alarmed by my presence thereby warning its partner with harsh loud cries.

Observation 10 and 11

During both of these 15 minute intervals no vocalizations or significant behavior had occurred. Also, the owls appeared to be relaxed. They showed no concern about my presence and most of the time they were in their nest burrows incubating their eggs.

Observation 12

At 24 seconds, Owl F squawked once which was clearly a statement of warning directed towards its babies. The urgency was obvious as Owl F assisted them back into the nest burrow.

At 740 seconds, Owl E squawked twice which appeared to be a type of warning call directed towards its partner F. Reinforced at 790 seconds when Owl F responded by squawking once and herding its babies back into the nest burrow. Once the babies were inside the nest burrow Owl F prevented them from leaving by spreading its wings blocking the only exit.

Observation 13

At 210 seconds, Owl F squawked once. This harsh loud cry could very likely have been a warning call directed towards its babies concerning my presence. It occurred while guiding them back into the nest burrow.

At 330 seconds, Owl B squawked once. Again, this harsh loud cry seemed to be a warning call about my presence directed towards its partner A. Both owls were repeatedly glancing at me and then at each other in an uneasy manner.

At 380 seconds, Owl B acknowledged my presence by vocalizing a single chirp and bobbing its head while staring in my direction.

At 460 seconds, Owl F squawked once while guiding its babies into the nest burrow. Obviously Owl F was warning its babies about my presence and protecting them from potential danger.

At 650 seconds, Owl B squawked once while staring in my direction then ran into its nest burrow. Apparently I was considered a threat as Owl B warned the other owls about my presence with a harsh loud cry then ran for shelter.

Observation 14 and 15

During both of these 15 minute intervals, no vocalizations or significant behavior had occurred. A possible explanation for this could be that the owls had slightly adapted to my presence. Support for this theory comes from the fact that I was the only visitor during both of these observations.

Observation 16

At 190 seconds, Owl B chirped once while focusing on my presence. As mentioned earlier this seemed to be a form of acknowledgment.

At 310 seconds, Owl B acknowledged my presence by vocalizing a single chirp and bobbing its head while staring in my direction.

Observation 17

At 870 seconds, Owl E chirped twice while focusing on my presence. These sharp sounds seemed to represent a distress call as the owl behaved in an uneasy manner.

Observation 18

During this 15 minute interval no vocalizations or significant behavior had occurred. As previously stated there is a good chance that the owls were slowly adapting to my presence. As before, I was the only visitor during this observation.

Observation 19

At 420 seconds, Owl C chirped twice. These short sharp sounds seemed to represent a distress call about my presence directed towards Owl F. At 480 seconds, Owl F responded with a warning call by squawking once. During this time of communication, both owls appeared concerned and threatened by my presence as they repeatedly glanced at me and then at each other. At 790 seconds, Owl A acknowledged my presence by vocalizing a single chirp and bobbing its head as it stared in my direction.

At 875 seconds, an extended pattern of calls (many chirps) were vocalized by Owl C while watching visitors. Again, I suspect this pattern of sounds must represent a distress call since the owl appeared to be distressed.

Observation 20

At 120 seconds, an extended pattern of calls (many chirps) were also vocalized by Owl A while watching visitors. Again, I believe this pattern of sounds must represent a distress call. The owl expressed a sign of desperate need by flying to its nest cavity and running inside for safety.

At 360 seconds, Owl C acknowledged the visitors' presence by vocalizing a single chirp and bobbing its head as it watched them very closely.

Observation 21

At 545 seconds, an extended pattern of calls (whee, chirp, chirp) were vocalized by Owl B apparently directed towards its partner A since they were facing each other. This pattern of sounds seemed to be a social call as the owls were interacting in a relaxed manner.

At 625 seconds, Owl B acknowledged my presence by chirping once and bobbing its head while looking in my direction.

Observation 22 and 23

Once again, during both of these 15 minute intervals no vocalizations or significant behavior had occurred. The owls appeared to be content and comfortable with my presence which adds support for the adaptation theory.

Observation 24

At 255 seconds, Owl E chirped twice while focusing on my presence. As mentioned before these sharp sounds seemed to represent a distress call as the owl was behaving in an uneasy manner.

At 360 seconds, Owl C vocalized a "whee" sound as it scanned the environment. Apparently, a chatter call since it was sporadic and seemed aimless.

Observation 25

At 430 seconds, Owl E squawked twice to warn Owl D about my presence. This vocalization seemed to serve as a warning of caution about my presence. They were in the middle of feeding and feared I might compete for their food source.

At 485 seconds, Owl D also squawked twice. Since one owl mimicked the other it is probably legitimate to label this a warning call.

Observation 26

At 670 seconds, Owl E squawked once while scanning the environment. This owl appeared to be agitated and concerned with its surroundings causing it to warn the other owls about the perceived danger with a harsh loud cry.

At 775 seconds, Owl C squawked once as it focused on visitors. The owl exhibited fear with a harsh loud cry most likely representing a warning call.

Observation 27

Once again, no vocalizations or significant behavior had occurred during this 15 minute interval. As in previous situations, the owls demonstrated adaptation by remaining calm when I was in their presence.

Observation 28

At 215 seconds, Owl F acknowledged my presence by chirping once and bobbing its head while looking in my direction.

At 570 seconds, Owl B squawked twice as it looked in my direction. The owl appeared concerned about my presence alarming the other owls with harsh loud cries.

At 665 seconds, Owl B chirped twice with its attention directed towards me. This was clearly a distress call showing concern about my presence.

At 690 seconds, Owl B squawked twice with its attention still directed towards me apparently perceiving a threat. Owl B warned the other owls of my presence and the potential danger.

At 720 seconds, 750 seconds, and 810 seconds an extended pattern of calls (many chirps) were vocalized by Owl B while staring in my direction. This pattern of sounds seemed to represent a distress call signaling concern about my presence. The owl was behaving in an uneasy manner.

At 840 seconds, Owl B squawked once which was again directed towards me. Owl B appeared threatened by my presence.

Observation 29

As the case many times before, no vocalizations or significant behavior had occurred during this 15 minute interval. Again, the owls seemed content and comfortable with my presence showing adaptation.

Observation 30

At 15 seconds, Owl B squawked twice to warn the other owls about my presence. Once again, Owl B was threatened by my proximity. This is not surprising since Owl B did not leave its nest burrow that often during the first few observations; thus, taking longer to adapt to my presence.

At 60 seconds, an extended pattern of calls (many chirps) were vocalized by Owl B while staring in my direction. Once again, Owl B was experiencing discomfort and felt threatened by my presence.

At 185 seconds, 300 seconds, 360 seconds, 450 seconds, 550 seconds, and 695 seconds an extended pattern of calls (a single squawk followed by many chirps) were vocalized by Owl B. The owl was extremely distraught and considered my presence a threat to its well-being.

Observation 31

At 160 seconds, a "whee"sound was vocalized by Owl D. This vocalization appeared to be a social call directed towards its partner C since they were facing each other and interacting in a relaxed manner.

At 250 seconds, Owl C vocalized many chirps seemingly directed towards its partner D. Once again, this pattern of sounds obviously represented a distress call signaling concern about my presence. The owl was behaving in an uneasy manner.

Observation 32

At 810 seconds, as I approached the cage Owl E squawked twice then flew away from me perhaps feeling threatened by my proximity.

Observation 33

As before, no vocalizations or significant behavior had occurred during this 15 minute interval. It was raining and again I was the only visitor, causing the owls to exhibit an adaptive behavior to my presence.

Observation 34

At 30 seconds, Owl D vocalized a "coo-coo" cry seemingly directed towards its partner C since they were facing each other. According to Spofford (1983), a "coo-coo" cry tends to occur at night, particularly during the breeding season. I believe this sound was vocalized at this particular time as the dark storming sky resembled night.

Observation 35

Once again, no vocalizations or significant behavior had occurred during this 15 minute interval. I was one of the few observers at this time providing the owls with an opportunity to demonstrate adaptation towards my presence.

Observation 36

At 25 seconds, Owl D vocalized an extended pattern of calls (many chirps) then flew away from the visitors seemingly threatened by their presence.

At 60 seconds, Owl D vocalized many chirps but this time as a response to visitors approaching its territory. The owl exhibited a sense of threat caused by the visitors' proximity.

Observation 37

At 250 seconds, Owl E squawked once while staring at visitors to warn the other owls about the perceived danger.

Observation 38

At 600 seconds, an extended pattern of calls (many chirps) were vocalized by Owl D while watching the visitors. This appeared to be a distress call since the owl was evidencing unease.

Observation 39 and 40

As many times before, no vocalizations or significant behavior had occurred during both of these 15 minute intervals. Once again, it was raining and I was one of the few observers which supports the theory that the owls were adapting to my presence.

Observation 41

At 875 seconds, Owl E squawked once as I approached the cage exhibiting unease with my sudden movement to an uncomfortable distance.

In conclusion, there are several different types of vocalizations each serving a specific function which were all previously mentioned. The data collected above reveals that almost all of the vocalizations were various versions of the chirp. It is also apparent that the most common vocalization was an extended pattern of many chirps. Also common, was the single chirp with a head bob to acknowledge another's presence.

Further research is needed to clarify the theorized functions of all the vocalizations I referred to. The "whee" sound or " whee, chirp, chirp" sometimes appear to function as a chatter call while at other times a social call. The only supporting research I discovered was by Safra, Constantine, and Goulka (1998), theorizing that a chirp with a head bob represents acknowledgment. However, additional research must be completed to test my theory on the function of the squawk and the chirp. It appeared clear to me that squawking was a warning of danger and chirping served to signal distress. Once again, further research could prove otherwise.

The most vocal individual was Owl B. This owl did not leave its nest burrow very often having less of a chance to adapt to my presence. Owl A on the other hand, was frequently outside of its nest burrow adapting more quickly to the presence of humans which explains its fewer vocalizations. Owl F rarely left its nest burrow causing it to be timid and very vocal in my presence. As for Owls C, D, and E, they left their nest burrows on a regular basis sometimes being quite vocal and other times not as much. However, all the owls showed adaptation by becoming silent when I was the lone observer or one of the few observers during an interval.

One vocalization I did not come across was the hiss. According to Rowe, Coss, and Owings (1986), when burrowing owls are cornered they produce a defensive hiss that functions as a Batesian mimic of a rattlesnake's rattle. Therefore, further study must be conducted in order to produce solid evidence for all the different types of burrowing owl vocalizations and their functions.

References

Canadian Burrowing Owl Recovery Team. (1995). National Recovery Plan For The Burrowing Owl (RENEW Report No. 13). Ottawa, Ont: Scientific and Technical Documents Division of the Canadian Wildlife Service.

Rowe, M. P., Coss, R. G., & Owings, D. H. (1986). Ethology.72 53-71.

Safra, J. E., Constantine, Y. S., & Goulka, J. E. (1998). The Burrowing Owl. In The new encyclopaedia Britannica (Vol. 2, p. 666) Chicago: Encyclopaedia Britannica.

Spofford (1983). The Burrowing Owl. In The encyclopedia Americana (Vol 5, p. 27) Danbury, Connecticut: Grolier International, Inc./Library of Congress in Publication Data.

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