Date of Award

January 2016

Degree Type

Open Access Thesis

Document Type

Master Thesis

Degree Name

Master of Science (MS)


Biological Sciences

First Advisor

Gary Ritchison

Department Affiliation

Biological Sciences

Second Advisor

David R. Brown

Department Affiliation

Biological Sciences

Third Advisor

Charles L. Elliott

Department Affiliation

Biological Sciences


When perched, several species of small falcons, including American Kestrels (Falco sparverius), often pump their tails, but the possible function of this behavior is unknown. My objective was to use observations and experiments to examine the possible function(s) of tail-pumping by American Kestrels. Fieldwork was conducted from March 2015 to December 2015 at the Blue Grass Army Depot in Madison County, Kentucky. During observations of focal kestrels, I noted their behavior (e.g., landing on a perch, hunting, or consuming prey), including when and how often they pumped their tails (i.e., rapid movement of the tail down, then back up to its original position). Kestrels typically tail-pumped when landing on a perch (mean = 4.1 ± 0.2 pumps per 10 sec) and consuming prey (mean = 2.4 ± 0.2 pumps per 10 sec). When hunting, kestrels tail-pumped at higher rates during the 30 sec prior to attacking (mean = 1.1 ± 0.3 pumps), then they did in the 30-60 sec interval before an attack (mean = 0.3 ± 0.1 pumps). During experiments where kestrels were presented with models of a conspecific and a predator (Cooper’s Hawk, Accipiter cooperi), I found no difference in likelihood of tail-pumping prior to and during the presentation. These results suggest that tail-pumping by American Kestrels is not used to communicate with conspecifics or as a predator-deterrent signal. Rather, kestrels appear to tail-pump to help maintain balance on perches when landing and consuming prey. In addition, prior to attacking prey, kestrels typically bob their heads (possible to aid in judging distances), and tail-pumping may help them maintain stability as they head-bob and prepare to attack.