WFO Funds Tricolored Blackbird Diet Analysis

Detail of painting by John Schmitt created for the Birdathon and used on the Birdathon T-shirt.

Western Field Ornithologists decided to dedicate $5,000 of the funds raised in the 2023 Birdathon to Tricolored Blackbird research and conservation efforts. A call was put out to the Tricolored Blackbird research and conservation community for worthy projects. The WFO Board selected a project to collect new information on the Tricolored Blackbird’s diet, using new DNA metabarcoding techniques.

The project is headed by Ian Souza-Coles, a scientist based in Audubon California’s Sacramento office. Ian is a recent addition to Audubon’s staff and has come up to speed quickly on Tricolored Blackbird biology and conservation issues. He recently assumed the role of co-chair of the Tricolored Blackbird Research Committee. Collaborators on the project include the Southern Sierra Research Station and California Department of Fish and Wildlife.

The project goal is to determine the taxonomic composition of Tricolored Blackbird dietary items through DNA metabarcoding of their feces. The project will focus on breeding adults in the San Joaquin Valley. Ian and collaborators expect to acquire 100–200 fecal samples over the course of the study. The study will fill a knowledge gap by quantitatively describing the diet and comparing the dietary composition between birds breeding at dairies and those breeding at wetlands.

The diet study builds off a broader study of Tricolored Blackbird movements to be conducted in 2024 and 2025. Hundreds of adults will be captured near their breeding colonies and fitted with Motus devices to track movements between various nesting areas occupied sequentially over the breeding season and to identify wintering movements. During the capture and handling process, birds often provide a fecal sample. So WFO’s funds will allow collection and analysis of these fecal samples—an efficient way to get many samples for lab analysis to identify plant and animal diet items, with little additional effort.

Dietary results will have conservation benefits for this threatened species. While habitat constraints are likely a major factor in their recent declines, Tricolored Blackbirds may also be negatively impacted by declining arthropod numbers that have been documented worldwide. A more comprehensive understanding of their diet, and how it differs in different landscape contexts, will tell us what food resources are most critical to this species and how we may manage habitat for greatest benefit.

Thanks to all who participated in the Birdathon as birding teams and contributors, who made this donation possible.

—Daniel Airola, past cochair, Tricolored Blackbird Working Group Research Committee

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