TIMOTHY F. WRIGHT, Ph.D.

Postdoctoral Fellow

tw98@umail.umd.edu

RESEARCH INTERESTS

My research concerns the mechanisms and evolutionary consequences of vocal learning in parrots. The parrots (Psittaciformes) evolved vocal learning independently of other avian orders and exhibit life-long learning in captivity. Thus they represent a promising model system for understanding the interactions between cultural evolution (change in traits transmitted by learning) and genetic evolution. Despite this promise, there have been few investigations of how parrots learn and use vocalizations, and what consequences learning has on the genetic structure of populations.

One research focus is patterns of natural variation in the vocal repertoire of  the yellow-naped amazon (Amazona auropalliata), a large parrot found in the tropical dry forest of Costa Rica. In collaboration with Jack Bradbury at UC San Diego, I discovered regional dialects in the contact call, the most commonly-used call in this species' repertoire. Subsequent work has shown that the acoustic structure of many classes of calls varies among these dialects. Playback studies suggest that these dialects are behaviorally salient for the birds, as foreign dialects fail to elicit responses by nest pairs while local dialects result in strong responses.  In my current position as a Smithsonian fellow, I am examining whether there are different patterns of geographic variation in sex-specific vocalizations used by males and females in their syntactically complex duets.

I have investigated the link between vocal variation and population structure using molecular genetic techniques. In collaboration with Jerry Wilkinson  at the University of Maryland, I  found strong evidence for unrestricted gene flow across dialect boundaries using DNA sequences from the maternally-transmitted mitochondrial control region. This result suggest that at least one sex, females, are dispersing across dialect boundaries and learning new calls upon arrival. My investigation of mtDNA variation in this species also led to the discovery of an unusual duplication of the control region in parrots, which is the subject of  ongoing collaborations with Jessica Eberhard of Louisiana State University. Currently in the Genetics Program, I am examining the extent of sex-biased dispersal in these populations by contrasting variation in mtDNA with variation in nuclear microsatellites. Such studies provide one avenue for he forces that promote vocal convergence and learning in parrots.

Another avenue is understanding how parrots perceive vocal signals. In collaboration with Bob Dooling at the University of Maryland, I have used psychoacoustic conditioning techniques with captive orange-fronted conures (Aratinga canucularis) to understand how they detect, discrimination, and categorization natural calls. We found that, as previously found in the budgerigar, the orange-fronted conure has an unusually low critical ratio, or ability to detect signals in noise, in the frequency range of its contact calls.  This result suggests that a low critical ratio may be a common adaptation to improve social communication in parrots. We have also examined discrimination of natural contact calls in this species and found that they quickly learn to classify the calls of different individuals by focusing on acoustic variation among individuals and ignoring variation within individuals.

A portion of my research effort is directed towards research into the conservation of natural parrot populations. The parrots contains more threatened species than any other bird family. The capture of young parrots for the pet trade is often cited as a primary cause for such high rates of endangerment, but its importance has been hotly debated , in part because there little published information describing rates of capture in natural populations. In collaboration with Cathy Toft, I collected 23 unpublished data sets on nesting mortality in Neotropical parrots to document capture rates. We found an average capture rate of 30% across all species in the study, a proportion that was significantly higher than natural rates of nest mortality. These data indicate that for many species capture for the pet trade is a substantial source of mortality. Currently we are investigating the effect of these elevated mortality levels on population viability using a modeling approach. To obtain a copy of the paper "Nest poaching in Neotropical parrots" published in Conservation Biology please contact me at tw98@umail.umd.edu .  For a copy of the data file on poaching rates in Excel format please click here. In addition, I serve as the Secretary of the Association for Parrot Conservation and act as moderator of the APC-LIST, an informational listserve for parrot researchers and conservationsists. Please e-mail me for more information about the APC and APC-LIST.

TEACHING

In Fall 2002, I taught a course in Animal Communication as an adjunct assistant professor at Georgetown University. This innovative course applies perspectives from a variety of disciplines, including physics, physiology, psychology, ecology and economics, to the study of animal communication. The classes are a mixture of lectures and student-led discussions of papers from the literature. Students also conduct group projects in acoustic analysis that culminate in oral presentations of their results. The syllabus for the course can be viewed at http://bioserver.georgetown.edu/undergrad/syllabi/biol353.html.

EDUCATION
 

Ph.D.     1997     University of California, San Diego    (Biology)

SELECTED PUBLICATIONS:
 

Lohr, B., T.F. Wright, and R.J Dooling. (in press)Detection and discrimination of natural calls in masking noise by birds: estimating the active space of a signal. Animal Behavior

Wright, T.F. K.A. Cortopassi, J. Bradbury, and R.J., Dooling.  (in press) Hearing and vocalizations in the orange-fronted conure (Aratinga canicularis). Journal of Comparative Psychology.

South, J.M. and T.F. Wright (2002) Nesting sex ratios in the yellow naped amazon: no evidence for adaptive modification. Condor 104:437-440.

Eberhard*, J.R., T.F. Wright* and E.S. Bermingham. (2001) Duplication and concerted evolution of the mitochondrial control region in the parrot genus Amazona. Molecular Biology and Evolution 18:1330-1342.            *Co-first authors

Wright, T.F. and G.S. Wilkinson (2001) Population genetic structure and vocal dialects in amazon parrots. Proceedings of the Royal Society B 268: 609-616.

Wright, T.F. and M. Dorin (2001) Pair duets in the yellow-naped amazon (Amazona auropalliata): responses to playbacks of different dialects. Ethology 107:111-124.

Wright, T.F., C.A. Toft , E. Enkerlin-Hoeflich, J. Gonzalez-Elizondo, M.Albornoz, A. Rodríguez-Ferraro, F. Rojas-Suárez, V. Sanz, A. Trujillo,S. Beissinger, V. Berovides A., X. Gálvez A., A. T. Brice, K. Joyner, J. Gilardi, S. E. Koenig, S. Stoleson, P. Martuscelli, J. M. Meyers, K. Renton, A. M. Rodríguez, A. C. Sosa-Asanza, F. Vilella, and J. W. Wiley (2001) Nest poaching in Neotropical parrots. Conservation Biology 15:710-720.

Wright, T.F. (1996) Regional dialects in the contact call of a parrot. Proceedings of the Royal Society of London B 263: 867-872.

Wright, T. F., E. Brittan-Powell, P. Mundinger, R. J. Dooling (in prep) Sex-linkage of heritable deafness and song frequency in the Waterslager canary. to be submitted to Proceedings of the Royal SocietyB

Bradbury, J.W., Wright, T.F. & K.A. Cortopassi. 2002. Parrots of the Area de Conservación Guanacaste, Costa Rica. http://www.acguanacaste.ac.cr/loras_acg/parrots.home.html

Wright, T.F. 2000. Protocols for DNA sequencing workshop: from DNA extraction to sequence alignment.

Revision: February 2003