The Wilson Journal of Ornithology 123(4):766-771, 2011 
TAIL PUMPING BY THE BLACK PHOEBE 
GREGORY F. AVELLIS 1 
ABSTRACT.—Black Phoebes (Sayomis nigricans) persistently pump their tails vertically while perched but the 
functional causes are unknown. I address four hypotheses about the function of this behavior in this species: (!) tail 
pumping aids in balance, (2) tail pumping enhances foraging. (3) tail pumping is a signal to territorial intruders, and (4) tail 
pumping is a signal to potential predators. The balance (mean ± SE; unstable substrates: 0.23 ± 0.024 pumps/sec. stable 
substrates: 0.22 ± 0.019 pumps/sec), foraging (non-foraging individuals: 0.28 ± 0.036 pumps/sec, foraging individuals: 
0.20 ± 0.026 pumps/sec) and intruder (pre-playback trial: 0.20 ± 0.025 pumps/sec. House Finch [Carpodacus mexicanus] 
control trial: 0.26 ± 0.029 pumps/sec. Black Phoebe experimental trial: 0.17 - 0.036 pumps/sec) hypotheses did not 
significantly explain tail pumping behavior. Tail pumping rules increased during predator sound playback (pre-playback 
trial: 0.23 ± 0.009 pumps/sec. House Finch trial: 0.26 ± 0.016 pumps/sec. Cooper's Hawk [Accipiter cooperii] trial: 0.61 
± 0.013 pumps/sec. post-playback trial: 0.35 ± 0.013 pumps/sec) and were accompanied by a high amount of both 
approaches (3.8 ± 0.8) and calls (6.7 ± 1.63). These results indicate that S. nigricans may be using tail pumping behavior 
as a pursuit-deterrent signal to advertise awareness to potential predators. Received 18 January 2011 Accepted 26 May 
A signal is any trait used for communication 
among individuals that modifies the behavior of a 
receiver and is useful to both the signaler and the 
receiver (Krebs and Davies 1993). Signals in 
many species can aid as a predator deterrent, 
territory defense, and/or in the context of sexual 
selection among other reasons. Avian tail move¬ 
ments may function in one of these contexts. 
Wood (1974) found a higher tail flicking rate in 
Common Moorhens ( Gallimtla chloropus) when a 
predator was nearby and Alvarez (1993) and 
Alvarez et al. (2006) noticed faster flicking rates 
in healthier individuals. Moorhen tail movements 
may operate in a sexual context as the study was 
performed before the breeding season, but 
Alvarez et al. (2006) suggested they function to 
provide information about physical condition to 
predators and require less energy than evading a 
predator. Murphy (2010) suggested tail wagging 
in Turquoise-browed Motmots (Eumontota super- 
ciliosa) may function in territory maintenance. 
Tail movements may not function as a signal 
but instead serve to enhance foraging or balance. 
Willie Wagtails (Rhipidura leucophrys) used tail 
movements when foraging because they startled 
and displaced insect prey (Jackson and Elgar 
1993). and Smith (1969) hypothesized that tail 
movements by Eastern Phoebes ( Sayomis phoebe) 
could help maintain balance. 
Black Phoebes (S. nigricans) persistently pump 
their tails by quickly lowering and raising them 
Northrifh'^Twi if California s,a,e University, 
USA Ntwdhoff Street, Northridge, CA 91330 
USA, e-mail: gregory.avellis.20@my.csun.edu '* ' 
766 
(Fitzpatrick et al. 2004) and the function of this 
behavior is poorly understood. The objective of 
my study was to demonstrate the potential causes 
of this behavior by testing the following hypoth¬ 
eses previously addressed by Carder and Ritch- 
ison (2009) for Eastern Phoebes: tail pumping 
aids in balance, enhances foraging, signals 
territorial behavior, and is a signal to predators. 
A hypothesis of a sexual context was not 
considered because both male and female Black 
Phoebes tail pump throughout the year (pers- 
obs.). 
The following predictions were made: higher 
pumping rates would be observed on ‘unstable' 
substrates, higher rates should be correlated with 
more foraging attempts and/or successful out¬ 
comes, Black Phoebes should tail pump at higher 
rates when a potential competitor is present, and 
faster pumping rates would be observed in the 
presence of a potential predator. 
METHODS 
Study Species.— The Black Phoebe is a small 
(16-18 g) insectivorous passerine bird that forages 
primarily in aerial sallies and often returns to the 
perch of origin (Fitzpatrick et al. 2004). Territorial 
males can often be heard singing, and are resident 
on the study area. 
Study Area. —All data were collected at sites in 
Wildwood Regional Park in the Anoyo-Conejo 
Valley, California, USA (34.2’ N, 118.9 W). 
“Lizard Rock' is an open grassland-type habitat 
consisting of mainly tall grasses, sparse bushes, 
and no tree canopy. ‘Oak Grove’ is a semi-open 
woodland habitat consisting of a moderate amount 
