UM Student Examines Bird Colonies in Namibia

Sociable weaver birds are indeed companionable creatures, living in groups of up to 500 in giant communal nests.

Gavin Leighton, a Ph.D. student in the Department of Biology in the University of Miami College of Arts & Sciences, spent the summer in Namibia, where he studied how weaver colonies work together to build and sustain these nests.

“I am investigating how weavers maintain large-scale cooperative behaviors without a top-down structure, and why the benefits of selfishness don’t erode cooperative nest construction,” he said.

A basic model of evolution by natural selection would suggest that each bird would collect as many resources as possible for itself to maximize its chances of surviving and passing its genes to future generations, Leighton explained, adding, “Seemingly, the best strategy is to let others do the cooperative work. We do not expect altruistic behaviors, but they are really pervasive.”

Professor William Searcy, the Maytag Chair in Ornithology in the Department of Biology and Leighton’s faculty advisor, said, “Gavin’s work is important in that it addresses the maintenance of public goods, meaning resources that are created through cooperation and made available to the population in general. The maintenance of public goods presents a puzzle because of the temptation to freeload – that is to use the resources without contributing to them.”
Searcy added that such public goods are common in human societies, but have not been studied extensively in non-human animals.

Weavers, which are about the size of sparrows, build the large nests to stay warm at night, when temperatures can dip below freezing. They line the nests with heat-holding materials such as feathers and soft grass, and crowd together into the warmest areas of the nest.

Building such substantial structures – which can surpass ten feet in width, four feet in height and 2,000 pounds in weight – requires cooperative construction activity. Many members of the weaver colony collect sticks and other materials and then weave them into the nests.

By identifying and tagging individual birds in the weaver colonies, Leighton has determined that the male weavers do the bulk of this work.

Using population genomics, or the large-scale comparison of DNA sequences in populations, Leighton determined that female weavers leave their natal colonies, while males continue to nest with birds to which they are related.

“They are helping their families,” he said, adding, “This is one way to sustain cooperative behavior: help relatives that also share the genes underlying cooperation.”

Searcy said, “Gavin’s results show that in his sociable weavers, individuals seem to be motivated to contribute to the communal resource largely because doing so benefits their genetic relatives.”

Leighton’s work is partially funded by a National Geographic Young Explorers Grant. This program offers opportunities for scientists aged 18-25 to pursue research and conservation projects. As a Young Explorer, Leighton writes about his study for the National Geographic News Watch blog.

This funding allowed him to bring an undergraduate student to Africa with him this summer, which helped him advance his work while mentoring a budding biologist.

“Direct research experiences are key to developing as a scientist,” he said.

Leighton taught in the College’s innovative introductory biology labs, supported by the Howard Hughes Medical Institute. Students in these courses have an opportunity to “engage in hands-on research experiences and conduct meaningful science,” he said.

Small groups of six students work directly with a faculty member to design and carry out an authentic research project; the labs are led by teams consisting of faculty, advanced graduate students (like Leighton) and advanced undergraduates. Halfway through the semester, the groups switch professors, allowing students to experience two different approaches and areas of expertise.

Searcy said Leighton excels in both the lab and the field. “Gavin, as a graduate student, is notable especially for initiative and independence. He came up with the idea of studying communal nesting entirely on his own, and then – on his own – learned the various techniques he needed to carry out the project and solved all the problems associated with working in Africa. The success of the project is a testament to Gavin’s abilities.”

Leighton expects to finish his Ph.D. this year, his sixth at UM. He earned his undergraduate degree from Colgate University.

Melissa Peerless can be reached at 305-284-2485.