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THE WILSON JOURNAL OF ORNITHOLOGY • Vol 123. No. 4. December 2011 
Pre-playback House Cooper's Post-playback 
Finch Hawk 
1 1(B) 
Pre-playback House Cooper's Post-playbad 
Finch Hawk 
Playback type 
Playback type 
07 (C) 
Pre-playback House Cooper's Post-playback 
Finch Hawk 
Playback type 
FIG. 4. The highest proportion of (A) calls and (B) approaches by Black Phoebes was observed when the Cooper's 
Hawk vocalization was played. (C) The highest tail pump rate was observed when the Cooper’s Hawk call was played. 
Different letters above error bars denote a significant difference by a Tukey post-hoc test. 
vigilance behavior. The results of my study suggest 
Black Phoebes are less successful at foraging when 
they are more vigilant. 
Signal to Territorial Intruders Hypothesis.— 
Black Phoebes pumped their tails at a significant¬ 
ly lower rate when an apparent intruder was 
detected, and may maintain their territory by 
chasing the intruder. Tail flicking by Moorhens 
was found to decrease after an individual was 
played a recording of a conspecific (Rtmdler 
2007). and Weeks (1994) observed that Eastern 
Phoebe territorial maintenance behaviors consist¬ 
ed of chasing the intruder while calling. 
Signal to Predators Hypothesis.— There were 
differences among the three sites. The greatest tail 
pumping rate was at 'Lizard Rock', an interme¬ 
diate rate at ‘Oak Grove’, and the lowest rate at 
Paradise Falls'. Raptors were observed soaring 
above 'Lizard Rock’ on several occasions but not 
above the other two sites. Thus, individuals in the 
exposed habitat of 'Lizard Rock’ may be under a 
greater amount of predation pressure and use tail 
pumping as a means to advertise awareness of 
predators. 
Black Phoebes tail pumped at significantly 
higher rates when a predator call was played, and 
approached the speaker and called more often 
during the predator’s call; these approaches and 
calls were positively correlated. Thus, Black 
Phoebes use tail movements as a signal to 
predators, probably as a correlate of intention of 
impending flight. Similarly, tail movements have 
been demonstrated as anti-predatory behavior in 
Common Moorhens, which tail-flicked more often 
not only when a predator was seen but also when 
it was heard (Randier 2007). Carder and Ritchison 
(2009) demonstrated that Eastern Phoebes tail 
pumped, called, and approached a visible predator 
at higher rates. My study demonstrates that sound, 
in addition to vision, is an important component in 
Sayomis signaling behavior as responses were 
observed at highest rates when a potential 
predator vocalized. Multiple cues used by prey 
to signal awareness of a predator have been 
