Research

When you walk down a hall, the familiar sounds of your own footsteps provides a simple observation: locomotion generates sound.

Animal Aeroacoustics

Courtship and Locomotion

Evolution of Behavior

Animal Aeroacoustics

We investigate the physical mechanisms by which air flowing over a feather or wing generates sound. Mechanisms include aeroelastic flutter, in which a feather oscillates at a stable frequency set by both its resonance frequency and the airflow.

We have in the lab:

An Acoustic wind tunnel (open jet, so that microphones can be out of airflow)
An acoustic cameras (localizes sound sources)
High speed cameras

Species studied:

Hummingbirds (hummingbirds are our specialty)
Great Gray Owl (collaboration with Jim Duncan in Manitoba)
Nightjars (collaboration with Nacho Areta in Argentina)
Flycatchers (collaboration with Nacho Areta in Argentina; also with Valentina Gómez-Bahamón.
Smithornis Broadbills in Africa

We are broadly interested in the physical acoustic mechanisms in play on animal wings, and how these sounds get converted into signals, or suppressed (in the case of quiet flight)

Courtship and Locomotion

We also study courtship display performance in its own right. Males of taxa such as hoverflies or hummingbirds attain high velocities, accelerations, or wingbeat frequencies in their aerial displays. We posit such behaviors become exaggerated through directional female preference for a dynamic male feature, similar to how female preferences for static features are thought to give rise to exaggerated morphology such as the elongated tails of birds or fish (Clark 2009; Clark 2012).

Research questions include:

Why do some hummingbirds nearly double their wingbeat frequency during displays?
What limits display performances?
How do males differ in their ability to perform displays?

Courtship displays can feature extreme behavioral performances not easily observed in other experimental contexts, and thus make interesting case studies of extreme performance per se.

Evolution of Behavior

Hummingbird courtship displays are also fascinating from the perspective of behavior. Over the past decade I have conducted fieldwork in ~13 countries in North Central and South America, most recently including Cuba and Argentina, trying to obtain display descriptions from every species in the Bee Hummingbird (Mellisugini) clade. Thus far this project has been descriptive:

Described new displays
Described new hybrid combinations
Split one hummingbird species into two

But we now have enough data that the bigger picture is now emerging. In the next few years we will use our data to examine:

How tail sounds coevolve with behavior
How behavioral components ('elements') of displays evolve
How nonvocal sounds coevolve with vocalizations
The role of Song Learning

Hybrid hummingbird-finder (and lab tech) David Rankin and I are investigating the phenotype of rare hummingbird hybrids such as Anna's x Allen's, Anna's x Costa's, and Black-chinned x Allen's that we have found in Riverside. David has found 5 such hybrids on and around the UCR campus in the past year alone.
Allen's x Rufous hybrid zone: we found a hybrid zone between Allen's and Rufous Hummingbirds, which we described in 2019 (Myers et al 2019). The hybrid phenotypes are quite interesting, since the displays that the two parent species perform are rather different. In collaboration with Alan Brelsford (UCR) and Kevin Burns (SDSU).

Other Projects

We have large outdoor aviaries and permits to work with hummingbirds. On campus we have Anna's, Costa's and Allen's hummingbirds year-round, plus Black-chinns from April-Sept. I'm happy to collaborate with anyone wanting to take advantage of these resources.

Ongoing projects include:

Pollination biology (in collaboration with Erin Rankin (Entomology, UCR)

References

Clark, C. J. 2009. Courtship dives of Anna's Hummingbird offer insights into flight performance limits. Proceedings of the Royal Society of London B 276:3047-3052.Clark, C. J. 2011. Wing, tail, and vocal contributions to the complex signals of a courting Calliope Hummingbird. Current Zoology 57:187-196.Clark, C. J. 2012. The role of power versus energy in courtship: what is the 'energetic cost' of a courtship display? Animal Behaviour 84:269-277.Clark, C. J. 2014. Harmonic hopping, and both punctuated and gradual evolution of acoustic characters in Selasphorus hummingbird tail feathers. Plos One 9:e93829.Clark, C. J. 2016. Locomotion-Induced Sounds and Sonations: Mechanisms, Communication Function, and Relationship with Behavior in R. A. Suthers, and T. Fitch, eds. Vertebrate Sound Production and Acoustic Communication. New York, Springer Handbook of Auditory Research.Clark, C. J., D. O. Elias, M. B. Girard, and R. O. Prum. 2013a. Structural resonance and mode of flutter of hummingbird tail feathers. Journal of Experimental Biology 216:3404-3413.Clark, C. J., D. O. Elias, and R. O. Prum. 2011a. Aeroelastic flutter produces hummingbird feather songs. Science 333:1430-1433.Clark, C. J., D. O. Elias, and R. O. Prum. 2013b. Hummingbird feather sounds are produced by aeroelastic flutter, not vortex-induced vibration. Journal of Experimental Biology 216:3395-3403.Clark, C. J., and T. J. Feo. 2010. Why do Calypte hummingbirds "sing" with both their tail and their syrinx? An apparent example of sexual sensory bias. American Naturalist 175:27-37.Clark, C. J., T. J. Feo, and K. B. Bryan. 2012. Courtship displays and sonations of a male Broad-tailed × Black-chinned Hummingbird hybrid. Condor 114:329-340.Clark, C. J., T. J. Feo, and I. Escalante. 2011b. Courtship displays and natural history of the Scintillant (Selasphorus scintilla) and Volcano (S. flammula) hummingbirds. Wilson Journal of Ornithology 123:218-228.Clark, C. J., T. J. Feo, and W. van Dongen. 2013c. Sounds and courtship displays of the Peruvian Sheartail, Chilean Woodstar, Oasis Hummingbird, and a hybrid male Peruvian Sheartail × Chilean Woodstar. Condor 115:560-577.Feo, T. J., and C. J. Clark. 2010. The displays and sonations of the Black-chinned Hummingbird (Trochilidae: Archilochus alexandri). Auk 127:787-796.Feo, T. J., J. M. Musser, J. Berv, and C. J. Clark. 2015. Divergence in morphology, calls, song, mechanical sounds, and genetics supports species status for the Inaguan hummingbird (Trochilidae: Calliphlox “evelynae” lyrura). Auk: Ornithological Advances 132:248-264.

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