Avian Alarm Communication

BIOL 4362 Laboratory 2 29 January - 26 February 2018 Avian Alarm Communication

Edward O. Wilson defines communication as the action on the part of one organism (or cell) that alters the probability pattern of behaviour in another organism (or cell) in an adaptive fashion (Wilson 1975). Such communication is critical to both intra and interspecific interactions, with properties of the communication system honed by natural selection to serve the fitness interests of the sender, receiver or both parties.

Among the many contexts in which communication occurs, perhaps the most critical to enhancing survival is alarm communication. In an alarm communication system, individuals encountering a noxious stimulus (such as a predator) issue an alarm response. Individuals that associate such signals with the danger at hand and that take appropriate action enjoy a considerable advantage, regardless of any payoff to the signaling individual. Thus, it is not surprising that alarm communication systems are essentially ubiquitous among mammals (e.g. Hare 1998), birds (e.g. Ficken 1990), amphibians (e.g. Hews 1988), fish (e.g. Chivers & Smith 1995), insects (e.g. Maschwitz 1966), and even plants (e.g. Crock et al. 1997).

In this lab, we will test for alarm communication in birds. While several studies have been conducted on this in the past (e.g. Evans et al. 1993, Evans & Marler 1994, Ratner & Boice 1971, Ressler et al. 1968, Wood et al. 2000), I will refrain from discussing prior findings to avoid biasing our results.

Methods General Considerations This study will test for the existence and specificity of alarm communication in black-capped chickadees (Poecile atricapilla). By contrasting behavioural responses of chickadees and other passerine birds to playbacks of black-capped chickadee calls, we will address multiple questions pertaining to avian vocal communication.

Comparing responses of birds to the "chicka-dee-dee" versus "gargle" and "high zee" vocalizations will determine whether these acoustically distinct vocalizations convey different information to call recipients. Quantification of differential behaviour in response to these calls should also allow us to interpret the function of these calls in nature. Contrasting the responses of members of different species to these playbacks will allow us to address the species-specificity of signals used in communicating various types of information. Finally, determining whether the propensity of call recipients to respond with calls of their own varies with the number of conspecifics present will address whether such vocal responses are reflexive or intentional (see Evans & Marler 1994).

You will receive instruction on the use of a field playback system in the lab on 29 January. Over the course of the next three weeks (29 January - 19 February), your group will be required to sign out a playback system, stopwatch and disc containing 30-second recordings of black-capped chickadee "chicka-dee-dee", "gargle" and "high zee" vocalizations and conduct a series of 3 playback trials at each of three unique locations 2

(locations separated by at least 1 km). At least four playback systems will be available for the groups in the class, and your group will be allowed to sign out a system for a 3-day block of time by contacting your course Teaching Assistant, Anna Mikhailitchenko. Each playback trial will require a total of 9 minutes, though trials within a given location must be interspersed by at least 15 minutes. As such, it is anticipated that data collection for this study will require a total of approximately 4 hours (3 locations x 1.33 h/ location), though additional time may be required to travel to the locations you chose to perform your playbacks. Data collected under the protocol described below will be consolidated to form a class data set, which you will then analyse and interpret to answer the questions posed in your assignment.

Experimental Protocol 1. Obtain and set-up the playback system in a wooded area or back yard where passerine birds are observed foraging. Note that if you're establishing the system near an existing bird feeder, ensure that the system and the observer(s) are situated at least 15 m away from the feeder. Allow five minutes for the birds to acclimate to the presence of the observer(s) and equipment. Note that observers should remain silent and avoid excessive movement so as not to influence the behaviour of the birds. 2. After the 5-minute acclimation period, record the number of individuals of all passerine species in general and the number of all black-capped chickadees seen over the next 2 minutes within approximately 20 m of your location. Further, keep separate tallies of the number of passerines in general and chickadees specifically that "investigate" the playback apparatus (we'll define "investigate" operationally as a bird approaching to within 5 m of the playback apparatus), and the numbers of passerines and chickadees that vocalize during the pre-playback period. I realize that it is difficult to distinguish birds as individuals, but do your best to include each individual only once in your counts! 3. Play a call track ("chicka-dee-dee", "gargle", or "high zee": order determined via randomization method of your choice prior to entering area) for its full 30 second duration, and record both the number of passerines in general and number of black-capped chickadees seen over 2 minutes (30 sec during and 90 sec after call) within the same area considered prior to playback. During the playback/post-playback period, also note the number of passerines in general and chickadees in particular that "investigate" the call (as defined above), and the number of both passerines in general and chickadees that produce a vocalization during the playback/post-playback period. 4. Wait a minimum of 15 minutes in the same area and repeat steps 2 through 3 (above) for a second of the three call types. Upon completion of that trial, wait an additional 15 minutes in the same area and complete steps 2 through 3 for the third and final call type. 5. Repeat the series of playbacks (steps 1 through 4) at two additional locations so that your group obtains three replicates of each playback type. 6. Submit your group's data to your course Teaching Assistant by 19 February 2018.

Assignment (10 marks, due 26 February 2018) 1. Produce appropriately labeled figures showing the mean±SE number of passerines in general and chickadees specifically that: a) were within 20 m of the observers before versus during and after the playback of each of the three call types (note in parts a through c that bird type - passerine general vs. chickadee could be displayed using different bar patterns or colors on 3

common axes, while time period – pre- versus during/post-playback – could be shown as discrete groups of bars on the abscissa so that there's one graph for each call type), b) "investigated" the playback apparatus before versus during and after playback for the three call types, and, c) vocalized before versus after the playback of the three call types. 2. Perform paired-sample t-tests (see Appendix) to evaluate the statistical significance of changes in: a) the number of passerines and the number of chickadees within 20 m of the observers before versus during and after the playback of the three call types (6 tests in total; 3 for passerines as a whole and 3 for chickadees), b) the number of passerines and chickadees that "investigated" the playback apparatus before versus during and after playback for the three call types (another 6 tests), and, c) the number of passerines and chickadees that vocalized before versus after the playback of the three call types (yet another 6 tests). 3. Did birds respond differently to the three call types we broadcast? Describe those differences with reference to the figures and/or analyses presented above. 4. Did any of the calls broadcast serve as alarm signals for chickadees or passerines in general? Be sure to indicate which calls functioned as alarm signals and describe the general nature of the alarm responses to support your answer. 5. Were chickadee alarm calls perceived as alarm signals only by chickadees? If not, explain why individuals may be selected to respond to alarm signals of other species. 6. Construct scattergrams contrasting the number of chickadees present during and after the playback of; a) "chicka-dee-dee" and b)"high zee" calls with the number of chickadees vocalizing during those time periods (one scattergram for each call type). Were chickadees more likely to vocalize when more conspecifics were present? Whether this trend is apparent or not in our data, what would a finding of this nature suggest about the behaviour of individuals producing alarm signals? 7. While playbacks of vocalizations prove quite useful in theoretical studies of animal communication, such playbacks also have several potential practical applications. In no more than one page, describe any one practical application in which the broadcast of animal vocalizations may prove useful.

References Chivers, D.P., & Smith, R.J.F., (1995). Fathead minnows (Pimephales promelas) learn to recognize chemical stimuli from high-risk habitats by the presence of alarm substance. Behav. Ecol., 6, 155-158. Crock, J., Wildung, M., & Croteau, R. (1997). Isolation and bacterial expression of a sesquiterpene synthase cDNA clone from peppermint (Mentha x piperita, L.) that produces the aphid alarm pheromone (E)-β-farnesene. Proc. Nat. Acad. Sci. U.S.A., 94, 12833-12838. Evans, C.S., Evans, L., & Marler, P. (1993). On the meaning of alarm calls: functional reference in an avian vocal system. Anim. Behav., 46, 23-28. Evans, C.S., & Marler, P. (1994). Food calling and audience effects in male chickens, Gallus gallus: their relationships to food availability, courtship and social facilitation. Anim. Behav., 47, 1159-1170. Ficken, M.S. (1990). Acoustic characteristics of alarm calls associated with predation risk in chickadees. Anim. Behav., 39, 400-401. 4

Hare, J.F. (1998). Juvenile Richardson's ground squirrels discriminate among individual alarm callers. Anim. Behav., 55, 451-460. Hews, D.K. (1988). Alarm responses in larval western toads, Bufo boreas: Release of larval chemicals by a natural predator and its effect on predator capture efficiency. Anim. Behav., 36, 125-133. Maschwitz, V. (1966). Alarm substances and alarm behavior in social insects. Vitamins and Hormones, 24, 267-290. Ratner, S.C., & Boice, R. (1971). Behavioral characteristics and functions of pheromones of earthworms. Psychol. Rec., 21, 363-371. Ressler, R.H., Cialdini, R.B., Ghoca, M.L., & Kleist, S.M. (1968). Alarm pheromone in the earthworm Lumbricus terrestris. Science, 161, 597-599. Wilson, E.O. (1975). Sociobiology. Cambridge: Harvard University Press. Wood, S.R., Sanderson, K.J., & Evans, C.S. (2000). Perception of terrestrial and aerial alarm calls by honeyeaters and falcons. Aus. J. Zool., 48, 127-134.

Appendix

In the present lab, we obtained data on the number of individuals performing certain behaviours or within certain distance criteria before and during/after the playback of specific calls. Thus, we will assume that the parametric assumptions are met (which they may or may not be!) and use paired-sample t-tests to evaluate whether the number of individuals changes between those time periods for each call type. Note this test assumes only that the distribution of differences was drawn from a population of differences following a normal underlying distribution.The test statistic for the paired-sample t-test is calculated as:

t = d / Sd where: d = mean difference between pairs of measurements (i.e. each pre-playback/post- playback pair gives a difference value d, and the mean of those difference is d), and Sd = standard error of d (given by S (of the differences) divided by √ n, the number of pairs). v, the number of degrees of freedom is given by n-1 (number of pairs - 1), and the critical value of t is obtained from any tabled distribution of Student’s t-statistic. 5