Slender-winged can be substituted with a variety of terms to accurately describe the physical appearance of certain creatures. One option is "narrow-winged," which conveys the same idea of thin and elongated wings. "Sleek-winged" is another option, emphasizing the smooth and streamlined nature of the wings. For a more poetic choice, "graceful-winged" or "poised-winged" could be used, capturing the elegance and balance of the creature in flight. Alternatively, "fine-winged" or "delicate-winged" suggest a fragility or sensitivity in the wings, while "aerodynamic" emphasizes the practical function of the slender wings for efficient flight. Overall, there are a variety of synonyms for slender-winged that can be used depending on the specific context and desired tone.