Perceptual mechanisms and sensory biases in sexual selection
Through a series of projects, students and I have been systematically investigating the abilities of birds to detect and respond to subtle variation in visual signals - most notably, how do birds detect and respond to very small amount of bilateral asymmetry (fluctuating asymmetry)? Given the great interest in whether fluctuating asymmetry plays a role in sexual selection, it is key to understand whether animals can actually detect these very small variations from perfect symmetry.

Doug Ruff investigated how European starlings process visual symmetry information and has performed experiments that determine how conspicuous asymmetries need to be for birds to detect these possible cues. Doug also worked on an empirical method to quantify signal detection thresholds for asymmetry in starlings. Laura Page, Alicia Frame, and Tori Long followed up on Doug's work to quantify, behaviorally, how starlings perceive quantified variation in plumage asymmetries. Asymmetries in compex traits probably need to be greater than 10% difference between left and right side before they can be detected..

Charles Johnson and Lauren Burns worked on a similar project to quantify how large size asymmetries have to be for birds to detect an asymmetric signal. These data indicate that the asymmetries generally need to be larger than 5% to be detected. Of all the asymmetry currencies we have investigated so far, size asymmetry is the most visually viable communication channel, as size asymmetries are often quite large in nature. This work is currently in press with Journal of Experimental Analysis of Behavior.

From the perspective of sensory biases, Judy Che and Earl Clelland completed a study which indicated that starlings can acquire a symmetry preference as a by-product of generalized learning processes, without ever seeing a symmetric object in their training procedures. Similarly,Carling Sitterley is completing a complex breeding experiment to investigate whether symmetry preferences can arise as a by-product of sexual imprinting in female zebra finches.

Lara McBride and Sabina Malhotra investigated how birds see video images. If birds can recognize each other on video screens, there are great potential benefits in terms of animal welfare, captive breeding and conservation programs (e.g. for imprinting or social learning). If birds respond well to video, this will also expand our options in terms of perception and behavioral studies. Results indicate that mate preferences displayed for video images are fundamentally different to preferences for live birds.

Amanda Houck followed up on these initial observations to explore whether social information about mating status can overturn a previously established mate preference. She also investigated the repeatability of these mate preferences and, together with Josh Rellick, assessing whether socially-acquired mate preferences can last for a long time in populations of zebra finches.

Earl Clelland has extended our knowledge of how female zebra finches acquire mate preferences through social mechanisms by demonstrating that females can alter a pre-existing preference for symmetry by watching males for just 10 hours. In addition, his project indicates that females need only to watch courtship by other females to change their mate preference.

Kelly Minton is investigating how a prior mating experience influences mate switching and subsequent mate preferences in zebra finches.

 

Parasites and pathogens influencing sexual ornaments and coloration
Alex Gunderson investigated whether communities of bacteria that reputedly degrade feathers on birds change the visual appearance and influence the fitness of individual eastern bluebirds. His data indicate that feather-degrading bacteria influence plumage color, but have fundamentally different consequences for males versus females. Male ornaments may be enhanced by bacterial degradation, but female ornaments are diminished. As the bacterial load of mated pairs are strongly positively correlated, Alex's data indicate that the bacteria may regulate some form of sexual conflict in this species - a form of parasite-mediated sexual conflict.

Alicia Frame collaborated with Alex and Mark Forsyth to investigate whether melanin pigments in feathers provide any protection against feather degrading bacteria. They provide the first unequivocal test which demonstrates that melanized feathers are more resistant to bacterial degradation, at least from the bacteria we tested. This work is soon to be published in Journal of Avian Biology.

 

Mutual mate choice in birds
Joey Hubbard has worked with Alex Gunderson, Jake Sequeira and other members of the ongoing bluebird field project to investigate whether there are aspects of mutual mate choice in eastern bluebirds. Specifically, she is interested in understanding whether females are ornamented and whether males choose among females on the basis of that ornamentation.

 

Human sexual selection
Gillian Reierson investigated how hormone levels (e.g. testosterone in men) may affect facial development and, subsequently, influence how women perceive these faces in terms of attractiveness and other socially important factors. In particular, Gillian demonstrated how testosterone influences facial shape and perceived dominance, but does not have the predicated effects on perceived dominance. Gillian's freshman project recently appeared in a major college textbook: Animal Behavior by John Alcock.

Desiree Brooke teamed with Gillian to expand these studies to look at the effects of estrogen on face perception. Estrogen is particularly intriguing as developed nations are heavily polluted with estrogenic compounds yet we do not know how such compounds are affecting facial development and social interactions. Potentially, we are feminizing populations without understanding the developmental and social implications.