Biology graduate student Jessica Krippel has spent three months on campus observing, catching, measuring, attaching identification bands and taking blood samples from 52 song sparrow couples and, under their anxious, protective watch, their chicks. The work is part of a study of songbird personality traits – primarily aggression among males – and the connection to reproductive success.
Although songbirds are primarily socially monogamous, nesting and raising children with one mate, they are not always “genetically monogamous” and engage in “extra-pair copulation,” said Krippel. (For nonscientists, that’s the biologically correct way of saying the birds have affairs.) Typically, more than 15 percent of sparrow offspring are “extra-pair young,” she said. Krippel and Jeremy Hyman, associate professor of biology, specifically designed the study to examine if more aggressive male song sparrows have more offspring.
“One possibility is that aggressive males do better in both regards – they get more EPCs (extra-pair copulations) and also protect their paternity at home,” said Hyman. “Another possibility is that they gain more EPCs from neighboring females, but while they are out, their females engage in EPCs with other neighboring males.”
To study the question, Krippel is spending the approximately four-month mating season mapping the songbird territories, finding nests, catching adults and babies, and taking blood samples to analyze paternity. In addition, Krippel and Hyman are conducting tests to measure aggression by determining to what degree a male songbird sparrow defends his territory.
Song sparrow territories on campus are about 20 yards apart, said Krippel. When defending them, males will sing and counter-sing, moving closer together. If the situation escalates, the birds grapple and peck at each other. Krippel has witnessed this level of combat only twice at Western Carolina.
“They try to avoid physical contact,” said Krippel.
Supporting the research project is a $500 grant from the High Country Audubon Society and a $500 matching gift from Bill and Peg Steiner. In addition, Krippel has received two graduate assistantships from WCU.
Also assisting on the project are two undergraduate students, Nicole Salzmann and Morgan Simril. Salzmann and Simril help watch the fine, specially-designed nets and traps used to catch the birds without harming – nets that must be monitored at all times. While they wait, they observe bird behavior or search for nests, which can be hard to find in the dense shrubbery, said Krippel.
She has come to know some birds better than others, such as “The Patriot,” named for his red, white and blue bands; “The Slacker,” who was late to settle a territory and mate; and “Stumpy,” who appears to have survived something that damaged his tail feathers.
So far, she has located nearly 200 chicks in nests that have yielded from one to five offspring each. In at least half of the nests, however, none of the chicks survive and the parents go on to re-nest. In one breeding season, birds may have three or four nests.
“They just keep trying if they fail,” said Krippel.
Krippel traces her interest in bird behavior to her parents, fellow animal lovers. She grew up enjoying training the family dog, a poodle named Candy, and showing American Saddlebred horses, including a horse registered as “Park Avenue” whom she nicknamed “Pac Man.”
“I enjoy the connection with animals and want to understand them,” she said.
After earning a degree in environmental science with a focus in biology from the University of Iowa, she moved to Western North Carolina and began working at the WNC Nature Center as a behavioral husbandry manager. In addition to using positive reinforcement to help animals with behaviors such as stepping on a scale, she assisted with enrichment activities, such as bringing novel smells or sounds into their environment.
As she considered the next career move, she spoke with Hyman about his research and study of behavior and aggression in song sparrows.
“My first question was ‘Does variation in aggression affect reproductive success?’ and he said ‘We don’t know that yet,’” said Krippel, who ultimately applied and enrolled in graduate school at WCU. “That’s how it started.”
People often stop with questions when they see her working on campus – the most common of which is if the parents will reject the chicks from the nest after she handles them. The answer is absolutely not, said Krippel.
“The babies are not gone for long – five minutes, and then they are back, but when I reach into a nest, the parents get upset,” said Krippel. “Some will run around with their wings up, and I’ve had them run after me before. I always feel so bad for them. I’ll say, ‘Oh, everything will be OK,’ and the parents go back to the babies as soon as I put the baby back.”
After analyzing the DNA this fall, she hopes to share the results of the research with a presentation for the High Country Audubon Society as well as at a behavioral ecology meeting and graduate research symposium. She will write a thesis and hopes the research will be published in a scholarly journal.
“My study will help to clarify if there is an evolutionary role of animal personality,” said Krippel. “Any trait, whether it be physical or behavioral, that affects the reproductive success of a species has evolutionary significance.”