Zebra Finch Macrophage Colony-Stimulating Factor (M-CSF) is a cytokine that regulates the development, proliferation, and survival of monocytes and macrophages in zebra finches (Taeniopygia guttata). M-CSF is produced by several cell types, including fibroblasts, epithelial cells, endothelial cells, and stromal cells, in response to tissue signals and inflammatory stimuli. Zebra finch M-CSF binds to the colony-stimulating factor-1 receptor (CSF1R), a receptor tyrosine kinase expressed on monocytes and macrophage lineage cells, activating intracellular signaling pathways such as PI3K–AKT, ERK/MAPK, and JAK–STAT that promote differentiation and maintenance of macrophage populations. Through these mechanisms, M-CSF supports macrophage-mediated immune surveillance, phagocytosis, tissue homeostasis, and inflammatory responses. Because macrophages play a central role in host defense, M-CSF–mediated macrophage function contributes to maintaining immune health and resistance to infection in zebra finches. In cell culture, recombinant zebra finch M-CSF is used to promote differentiation of monocytes into macrophages and to support macrophage proliferation and functional assays in vitro. Zebra finches are widely used as a model organism in avian biology and neurobiology, making M-CSF useful for studying macrophage biology, immune regulation, and immune–neural interactions in avian research systems.