By Teen Volunteers Peter Covert, Lara Tseng, and Yunjiao (Grace) Xiao
We met over Zoom to decide on what project we wanted to work on together as a group. Since everyone had a strong interest in avian science and analyzing data, we decided to focus on SFBBO’s Colonial Waterbird Program data. Through the Colonial Waterbird Program, SFBBO biologists and volunteers have been tracking numbers of breeding herons, egrets, terns, gulls, and other birds that nest in colonies around the Bay Area since 1982. This program provided us with a large body of data and a variety of ideas for how we could interpret it.
WHAT WE DID & WHAT WE FOUND
We studied 26 well-established colonies of various shorebirds and other waterbirds (interactive map). For each of these sites, we collected data on which plants the birds nested on. We tried to identify the plants by collecting photographs and notes from Colonial Waterbird Program volunteers while also using various outside identification resources such as iNaturalist. From here, we were able to observe certain trends between the birds and their nesting tree species.
We found that there was no significant difference between the preferred tree for each studied bird species. However, we did notice a high percentage of colonies using Eucalyptus trees (which are nonnative) for nesting sites. For other plants, the usage was roughly evenly split between native and nonnative plant genera.
Proportion of links of each bird species by tree genus, where BCNH = Black-crowned Night-Heron, GREG = Great Egret, SNEG = Snowy Egret, and GBHE = Great Blue Heron. The series in blue represent native trees, and the series in red represent nonnative trees. Note the great overrepresentation of Eucalyptus species.
WHY DO THESE RESULTS MATTER?
Our results find relevance in the environmental debate over whether Eucalyptus in the Bay Area should be removed. Currently, the debate for and against the removal centers around two issues: the potential fire hazard that trees of the genus Eucalyptus present, and the threat it poses to native mixed-woodland biodiversity. Since our study shows that these trees are widely used by native waterbird populations, it might be worth considering retaining certain swaths of Eucalyptus intact to sustain healthy riparian communities. More investigation is needed to determine the best practices for conserving our native biodiversity and ensuring public safety. It would also be interesting to compare the data of bird-tree pairings with the local tree distribution to find a baseline of the relative local abundance of each tree species. This can give us a clearer picture of trends that might exist between bird species or across regions.
SOME CHALLENGES WE ENCOUNTERED
When conducting this study, we encountered challenges that could impact the results. First, identifying the plant species was difficult in many cases due to unavailability of photos or poor quality of photos. When we could not identify the plant species, we excluded the site from our study, which could bias the results. The Colonial Waterbird Program also relies on volunteers to record colonies present at different sites throughout the Bay Area, and lack of volunteer availability can affect the consistency of the data. For example, COVID-19 restrictions impacted the ability of volunteers to assess all the sites. Due to these challenges, we ended up with a small sample size, so our results might not be representative of overall trends in the Bay Area. Nonetheless, our study provides an example of how long-term data collection by scientists and community members can be used to explore questions relevant to avian conservation.
Read the full project report here. Thanks to the other Teen Volunteer Program members who helped work on the early stages of this project: Sierra Glassman, Vayun Tiwari, Philip Yang, Sebastien Jeantet, Sahithi Adiraju, and Royce Lee.
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