Anthony Zambella Biology 544: OrnithologyTA: Amy StraussApril 20th, 2015

Do species flee upon hearing a call from a non-native bird of prey species? A close look on flight responses in Poecile atricapillus and Baeolophus bicolor

Introduction:

It is common knowledge amongst ornithologists that birds have many methods to respond to different stimuli, whether the stimulus is visual, auditory, or in some rare cases released chemically. Birds use vocalizations to communicate to each other conspecifically in situations such as territorial defense, mate attraction and dominance hierarchy, but also use other species calls as a way to assess the environment they are in (Dooling et al 1992). It is known that different avian species will ephemerally abandon their young if they suspect that a predator is close by (Schaef et al 2012, Ellis-Felege et al 2013). That being said little is known how birds would react to bird of prey vocalizations they would not normally hear in a natural setting.

This experiment is aimed at pointing out flight responses of the Black Capped Chickadee (Poecile atricapillus) and Tufted Titmouse (Baeolophus bicolor) upon hearing a call from both a native and non-native species bird of prey. Both Poecile atricapillus and Baeolophus bicolor are small seed eating birds in the family Paridae. These both work together, in conjunction with other species in what is known as mixed-species flocks to forage and better their predator avoidance (Krebs 1972). Not only is this experiment attempting to see if simply a hearing stimulus from a native bird of prey, Cooper’s Hawk (Accipiter cooperii) will elicit a flight response, but also if they will respond to a call from a non-native bird of prey, the Red-Footed Falcon (Falco vesterrinus), a near-threatened status bird in the family Falconidae that is indigenous to eastern Europe and Asia.

Based off of previous knowledge of both the Black-Capped Chickadee and the Tufted Titmouse, I predict that both passerines will exhibit a flight response upon hearing the call from the Cooper’s Hawk, while they will either show a reduced flight response or no flight response at all upon hearing the call of the Red-Footed Falcon.

Methods:

This experiment was performed in Georgetown, Massachusetts (see figure 1), a rural town 40 minutes north of Boston. There were four tube feeders used in this experiment, each spaced 10 feet apart (~3 meters) using birdseed packs predominately containing black oil sunflower seeds. The speakers used for the auditory feedback portion of the experiment were two JBL JRX115 15-Inch 250W continuous two-way loudspeakers. These speakers were placed 30 feet away from the tube feeders. Observations were taken a total of twenty times (ten days total) at two times during each day (9am and 5pm) on the dates of February 7th and 8th, 21st and 22nd, March 21st and 22nd, and April 4th, 5th, 11th and 12th 2015. To ensure time of

day was not a factor affecting the results, both the Cooper’s Hawk call and the Red Footed Falcon call were played in an alternating fashion each day; Cooper’s Hawk call was played a total 10 times in the morning and 10 times in the afternoon, as well as the Red Footed Falcon call. As the two species were observed on and around the feeders, the call would be played through the speakers for thirty consecutive seconds followed by an assessment of the feeder area for ten minutes, using

binoculars from a distance to not disturb the potential activity of the birds.

Results:

Of the 20 total times recorded, the Black Capped Chickadee was seen at the feeder 20 times. Of the ten total times the Cooper’s Hawk was played, The Black-Capped Chickadee fled a total of 8 times. The Tufted Titmouse was observed at the feeder 16 out of the 20 recorded times. Of the 8 times the Titmouse was seen at the feeders during the Cooper’s Hawk call, it fled 6 times. Of the 10 times the call from the Red-Footed Falcon was played, both the Black-Capped Chickadee and the Tufted Titmouse fled 2 times. The two occurrences in which the Black-Capped Chickadee and the Tufted Titmouse fled upon hearing the Red-Footed Falcon call, they were both seen fleeing together. When the birds fled from either call, the average time to return to the feeders was about seven minutes, however sometimes neither the Black-Capped Chickadee nor the Tufted Titmouse would return at all for the rest of the afternoon. Please see figures 2.1 and 2.2 below for the aforementioned data.

Figures:

Figure 1. Map of location where experiment was held (Georgetown, Massachusetts, Latitude 42.734, Longitude -71.009)

Figure 2.1: Flight responses observed in Poecili atracipillus and Baeolophus bicolor.

Figure 2.2: Data table recording flight responses.

Figure 3: distributions of the three local species studied

Figure 4: current distribution of Falco vespertinus

Discussion:

Based on the data collected from the twenty recordings, regarding the call from Accipiter cooperii, It can be safely concluded that there is some correlation between bird of prey calls and the triggering of a flight response in the Black Capped Chickadee and Tufted Titmouse. With regards to Falco vespertinus, the species that is not seen in North America, there was a general trend showing that the auditory stimulus of their call alone did not elicit a flight response in the Black Capped Chickadee nor the Tufted Titmouse. The most likely reason for this result is that the

Black-Capped Chickadee nor the Tufted titmouse have not been exposed to the Red-Footed Falcon or its vocalizations, and as such do not pick the call up as a stimulus that a predator is in close proximity. Another possible (though unlikely) reason for this result is that the call was either too soft or too loud, thus confusing the birds or resulting in them ‘drowning’ out the noise and not picking it up as an avian vocalization.

The two times that the Black-Capped Chickadee and the Tufted Titmouse ignored the call of Accipiter cooperii were spaced far apart, about two months, suggesting that either they did not hear the call or that the call was too loud thus not being picked up as an avian call.

It is interesting to note that, although the two passerine birds studied in this experiment did not respond much to the call of Falco vesterrinus frequently, when they did they fled together, supporting the idea of mixed species flocks working together and aiding each other with increased vigilance and more time to forage. Because the two times the Black-Capped Chickadee and the Tufted titmouse were in early to mid spring, there is a possibility that they could have picked up the auditory stimulus as and confused it with an endemic bird of prey species that may migrate up north for breeding season.

Notable issues that arose with this experiment should be considered before replicating it. One possible amendment to the experiment would be to add in a control noise, as it was not always clear if the noise itself was scaring the birds away or if the predatory calls were. This follows into my next suggestion to future scientists replicating this experiment: the volume of the call should be carefully monitored and kept consistent throughout the experiment, as a variation in volume could be a large variable that would skew accurate results. One problem faced with the procedure was that feeding times of the birds were inconsistent; some days the feeders would be swarmed with all different birds, and on others they would be deserted.

Bibliography (literature used as knowledge resource during experiment):

1. Dooling, Robert J.; Brown, Susan D.; Klump, Georg M.; Okanoya, Kazuo. Auditory perception of conspecific and heterospecific vocalizations in birds: Evidence for special processes.Journal of Comparative Psychology, Vol 106(1), Mar 1992, 20-28. http://dx.doi.org/10.1037/0735-7036.106.1.20

2. Schaef, KM et al. Predator Vocalizations Alter Parental Return Times at Nests of the Hooded Warbler. Nov 2012.

3. MacLean, Sara H and Bonter, David N. The Sound of Danger: Threat Sensitivity to Predator Vocalizations, Alarm Calls and Novelty in Gulls. 6 Dec 2013.http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0082384

4. Krebs, John R. "Social Learning and the Significance of Mixed-species Flocks of Chickadees." NRC Research Press. Canadian Journal of Zoology, 23 July 1973. Web. 10 Mar. 2015.

5. Yorzinski, Jessica L. and Patricelli, Gail L. Birds Adjust Acoustic Directionality to Beam their Antipredator Calls and Conspecifics. The Royal Society. 2009. http://rspb.royalsocietypublishing.org/content/early/2009/11/18/rspb. 2009.1519

6. Schaef, KM et al. Predator Vocalizations Alter Parental Return Times at Nests of the Hooded Warbler. Nov 2012. http://apps.webofknowledge.com/full_record.do?product=WOS&search_mode=GeneralSearch&qid=5&SID=3D7M1VV9UXBwMeTDqlI&page=6&doc= 53

7. Ellis-Felege, SN et al. Fight or Flight: Parental Decisions about Predators At Nests of Northern Bobwhites. American Ornithologists Union. 2013; 130(4): 637-644. http://apps.webofknowledge.com/full_record.do?product=WOS&search_mode=GeneralSearch&qid=5&SID=3D7M1VV9UXBwMeTDqlI&page=3&doc=29

8. "All About Birds." All About Birds. Cornell Lab of Ornithology, n.d. Web. 16 Apr. 2015. (Species distribution maps used from here)