SCHUYLKILL HAVEN, Pa. — At a regional conference, recent Penn State graduate Joseph Medica and rising senior Bethany Hollenbush, both past and current biology majors at the Schuylkill campus, and Lucas Redmond, assistant professor of biology at Penn State Schuylkill, have recently presented findings of their research at a regional conference. The multi-year research project, focused on the gray catbird population located on and adjacent to the campus was presented at the 2021 Northeast Natural History Conference, hosted in conjunction with the Wilson Ornithological Society and the Association of Field Ornithologists’ annual meetings.

Hollenbush and Medica each delivered poster presentations, and Redmond, the students’ faculty adviser, also delivered a talk at the conference.

Nest success and nest-site characterization in gray catbirds

Hollenbush’s presentation, “Nest Success and Nest Site Characterization in Gray Catbirds,” reviewed the birds’ nest-site selection and success in a population of catbirds located on and around campus. The field research was conducted during the gray catbirds’ breeding seasons from early to mid-May through late May and early June between 2016 and 2019.

Once the catbirds arrived at the study site, the research team conducted daily surveys of the area to locate as many breeding pairs of birds and their nests as possible. Once they located these nests, they would check in on them every three to four days to determine if the nests were successful or had failed.

After nest fate was determined, nest-site surveys were conducted to measure characteristics of the nest site and its surrounding habitat, including height and diameter of shrubs where nests were placed, nest height, orientation, concealment, and canopy area.

The researchers employed the program MARK, which provides parameter estimates from marked animals when they are re-encountered later, to estimate daily survival rates and understand how nest success varied. Across the period of this study, approximately 47% of catbird nests were successful, and their MARK analysis indicated that daily survival rates of catbird nests varied yearly and tended to decline as the breeding season progressed. 

Hollenbush’s presentation also examined the type of vegetation in which the catbirds constructed their nests. “Our characterization of nest sites indicated that catbirds on our study site primarily utilized three species of invasive woody shrubs: multiflora rose, Tartarian honeysuckle, and privet,” she said in her presentation abstract. “Nest height exhibited some difference among these three species, with nests placed in privet being higher than those in rose, while nests in honeysuckle were intermediate in height. Aside from these findings, we found no other consistent differences in nest placement among the three species of shrub used.”

This presentation earned Hollenbush a finalist designation in the conference’s student poster competition. “Although I was nervous about presenting to people much more experienced than myself, my poster received great comments from the judges. That conference was good practice for my next presentation at the American Ornithological Society in August,” she said.

In the future, Hollenbush and Redmond plan to combine the MARK analysis with the nest-site characteristics to determine if any of the nest-site characteristics influence nest success.

“When I started doing research on gray catbirds with Dr. Redmond in spring 2020, I wasn't expecting to find a field I was so invested in. From doing this research, I have found something I can see myself doing in the future,” Hollenbush commented. “Every day is something new, and it never feels like work to me because everything is so interesting.”

Gray catbird parental care

Medica’s presentation, “Gray Catbird Parental Care,” examined the ways in which the birds cared for their eggs and young, including incubation, brooding, provisioning of young, and nest sanitation. In his abstract, Medica explained that this care requires a tremendous investment of the birds’ energy, but ultimately increases the chance of successful reproduction.

In his research presentation, Medica outlined that the behaviors birds engage in, such as nest sanitation and provisioning, may be exhibited by both sexes, while other behaviors, such as incubation, may only be performed by one of the sexes. For example, females of some species may provision offspring at higher rates than the males they are paired with. In general, Medica explains, gray catbirds are socially monogamous, multiple-brooded, open-cup nesting songbirds that exhibit biparental care.

“We used remotely placed cameras at catbird nests to record and quantify feeding rates of males and females,” Medica wrote in his abstract. “Based on patterns observed in other songbirds, we predicted that female catbirds would feed at higher rates than males, but we found no difference in feeding rates among years, and within years, feeding rates did not change across the breeding season.” In contrast with other songbirds, the researchers discovered that male catbirds fed their young at rates approximately 1.5 times greater than the females they were paired with, and male feeding rates were positively related with nest success.

“Our results suggest that the male catbirds have a much larger role in the parental care than was previously anticipated, as well as an integral role in determining the fate of their young,” Medica concluded.

This May, Medica earned his bachelor’s degree in biology, and assisting Redmond with his research is something he did throughout most of his undergraduate experience at Penn State Schuylkill. “I have learned more from my work with him than I thought was possible outside of a classroom, and I realized that I learn much better when I work through things with my hands than I do in a lecture,” Medica reflected. “I also was able to discover my passion for ecology and working with birds, especially doing research out in the field.”

“Participating in the NENHC conference allowed me to develop my presentation skills further, as well as allowing me to interact with other professionals in the field and narrow down possible routes for my independent research under Dr. Redmond,” he said.

Factors influencing clutch size and egg mass in gray catbirds

In addition to the students’ presentations, Redmond delivered a talk regarding the team’s gray catbird research. His presentation, “Factors Influencing Clutch Size and Egg Mass in Gray Catbirds,” discussed the findings of the field research he conducted between 2016 and 2020.

According to Redmond’s abstract, laying larger and more eggs is an important energetic investment by female birds into their young. “Larger eggs should result in nestlings that are larger at hatching and, thus, can presumably leave the nest sooner, thereby reducing the likelihood of nest predation. Larger clutch sizes should result in more young fledged, and, thus, increase female fitness,” he explained.

Over several years, Redmond studied variation in clutch size and egg mass in the same population of gray catbirds that his students researched. The results of his study indicated that clutch size in catbirds declined across the breeding season. He also found that as catbirds lay fewer eggs as the breeding season progressed, they invested more heavily in individual eggs by laying heavier eggs.

Moving into the 2021-22 academic year and beyond, Redmond will continue his work on this population of catbirds. During the summer of 2021 he will continue working with Bethany Hollenbush so she can further her experience with field work. In addition, rising junior Grace Muench, a biology major, will be joining his research group.

“Doing research with undergrads is, without doubt, the best part of my job,” said Redmond. “This last year has been difficult because I've had limited contact with my students, so we've had to adjust how data were gathered. But in the end, I’m pleased we were still able to present our work.”

Undergraduate involvement is key to Redmond’s work. For their part, students are given the opportunity to conduct smaller-scale projects, like those described here, that fit into the larger context of his research and increase the quality of their experience at Penn State Schuylkill.

To learn more about Penn State Schuylkill’s biology program and undergraduate research opportunities, visit schuylkill.psu.edu/biology.