David W. Bradley


I have been fortunate enough to have worked on avian ecology research projects in a number of countries, specifically in Latin America (Costa Rica, Peru, Panama, Mexico, and Colombia).  I have also assisted on projects in the United States and here in Canada


Recently I took part in a investigative research trip to Colombia to work with local ornithologist Sandra Valderrama.  Sandra is a well known biologist who has studied the critically endangered Niceforo's Wren.  Her goal is to protect this species on the brink of extinction by understanding is biology, in particular its vocal behaviour.  In this study we were recording the vocalizations of a very closely related species of bird, the Rufous-and-white Wren.  More specifically we were recording the minlosi subspecies of this bird which Niceforo's Wren probably recently speciated from.

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Costa Rica

My current graduate research interests stem from my fascination and adoration of birds.  From an early age I marvelled at their diversity of form and behaviour.  Although my interests vary widely in the field of avian biology, currently I am interested in avian communication.  More specifically I would like to determine the way in which coordinated group displays by birds living and breeding cooperatively function in maintaining social bonds and establishing resource ownership.  My study species is a feisty tropical songbird, the Rufous-naped Wren (Campylorhynchus rufinucha).  This bird occurs in the dry forests of Central America from Mexico in the north to Costa Rica in the south.  They live in extended family groups that live and defend all purpose, year-round territories.  They sing rich and varied songs of pure whistles interspersed with harsh barks, chatters and rattles.  Songs are sung as solos, duets and choruses and it is this diversity of song contributors that I am most interested in

My study site is in Parque Nacional Santa Rosa in Guanacaste Province of northwest Costa Rica.  Here I follow and record the songs of family groups.  I will use these data to determine if families use certain distinct songs that encode group membership and identity.  This coming field season in Costa Rica I will perform song playback experiments to assess the relative roles of  songs performed by single birds, duetting pairs and by larger family groups.

Click here to hear an example of a Rufous-naped Wren song from Costa Rica.

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Recently I took part in a collaborative research project with Dan Mennill (my graduate thesis advisor), Stephanie DoucetPeter Slater of the University of St. Andrews, and other graduate students from the University of Windsor on the vocalizations of the Inca Wren (Thryothorus eisenmanni).   Inca Wrens have a very restricted distribution, occurring only in montane bamboo scrub in the immediate vicinity of the stunning ruins of the historic city of Machu Picchu, Peru.  They are a songbird of the genus Thryothorus, some of the most accomplished singers in the bird world.  Inca Wrens live in small family groups of 2-6 birds and sing loudly in a highly coordinated vocal chorus to defend their territories.  It was therefore our research goal to record the songs of this marvellous bird and determine how the individual birds contribute to the chorus and how this differs from other closely related species.  It has been shown that the Inca Wren's closest relative, the Plain-tailed Wren (Thryothorus euophrys), sings in highly coordinated choruses of up to 7 birds, with males and females each contributing different alternating parts.  Our recordings of the Inca Wrens at Machu Picchu will be used to write a descriptive scientific paper 0f their vocalizations and in a comparative paper of the entire thryothorus genus. 

Click here to hear an example of an Inca Wren song I recorded at Machu Picchu.

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In 2005 I worked as a project supervisor on a comparative study of avian life histories in Panama.  This NSF funded project is known as the Life History-Physiology Nexus, a comprehensive comparison of the physiology and behaviour of tropical and temperate organisms.  Researchers from the University of Illinois, Princeton, UC Davis, Ohio State and Oregon State University collaborate on this study to assess a fundamental prediction of life history theory: that extended breeding seasons and low adult mortality select for a slower pace of life in the tropics, which manifests as lower parental investment in offspring and higher allocation of resources to adult maintenance.  The study site for this project was in and around the town of Gamboa, in the former canal zone of central Panama.  I was involved in locating and monitoring multiple species nest sites to collect baseline breeding data such as clutch sizes, timing of incubation and breeding densities.  I also set up video cameras on nests to determine the frequency of incubation and chick feeding bouts as a measure of parental investment, measured developing chick morphometrics such as growth rates and conducted neophobia experiments on nests.  We also maintained an egg incubator in our lab to determine if the rate of egg development is constrained by the constancy of temperature and humidity around the egg and provide base-line hatching periods.

In 2003 I assisted in the project of a fellow student, Janeene Touchton, on her graduate research project in Panama.  We were interested in assessing the effects of competitive release on the foraging dynamics of ant-following antbirds.  Specifically we were comparing foraging dominance interactions at ant swarms at 2 different sites, one of which had undergone the local extirpation of a large dominant species. Our study sites were located in the former Canal Zone of central Panama, in an around the large man-made Gatun Lake that forms the majority of the current passage between the Atlantic to Pacific Oceans.  Our treatment site was the long-term Smithsonian research station on Barro Colorado Island and the mainland adjacent site in Soberania National Park.  For this project I captured our study species, Bicoloured, Spotted and Ocellated Antbirds, and applied unique, coloured leg bands.  This allowed me to conduct focal behavioural observations on each species as they foraged on flushed arthropods at army-ant (Eciton burchelli) swarms.  I also collected blood samples from all the birds I captured for use in future genetic studies.  To some birds I applied small radio transmitters and with the aid of radio telemetry equipment located and tracked active ant colonies.

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In the summer of 2004 I worked with Joe Fontaine on his PhD research at Oregon State University.  His project was a study on the effects of post-wildfire salvage logging on the unique wildlife of the Siskiyou Mountain in South-west Oregon.   The work involved a regular census of the birds, small mammals and vegetation in each treatment area, with varying levels of burn severity and salvage intensity.  It was a great way to experience this fascinating landscape and learn some novel field techniques such as mammal trapping using Sherman traps.

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I was very fortunate in 2003 to receive funding through UBC to assist on a research project  in Chiapas, Mexico.   I worked alongside José-Luis Rangel-Salazar who was conducting his PhD research on the demography and habitat selection of tropical resident and neotropical migratory birds.  More specifically he wanted to know how closely related birds partition resource use in the same habitat.  The resident Ruddy-capped Nightingale-Thrush (Catharus fratzii)  and the migratory Swainson's Thrush (Catharus ustulatus) both live in the cloud-drenched mountain forests surrounding San Cristobal de las Casas.  My role in this project was in capturing, measuring and applying colour bands to the legs of these two species.  The findings of this work was recently published by Jose and other researchers in the journal Ornitologia Neotropical.

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My first field work positions were with Kathy Martin at the University of British Columbia on her NestWeb project up in the Caribou-Chilcotin region of Central British Columbia.  This study is a long term assessment of the dynamics of a community of cavity-nesting birds, such as woodpeckers, chickadees, ducks, swallows and owls.  This taxonomically diverse guild of birds all nest in holes in trees and it is the use and reuse of these holes that is the central research goal of this project.  In the summers of 2001 and 2002 I assisted on this project in various roles.  I was primarily involved in locating and monitoring nesting activity, performing population censuses and capturing and banding birds.  In an effort to assess the impact of Mountain Pine Beetle infestations in the area, I also performed rigorous vegetation sampling.  This project was a great start for me in my career where I learned many of the ins and outs of ecological research.

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