The shape and color of the egg can help determine who owns the nest. A round or elliptical shape is more likely to belong to a nesting bird, while an egg with a pointed end is more typically found in a predator's nest. The color may also be indicative of the owner. If the egg is light green or blue, it may indicate that it belongs to a baby bird; if it's dark, brown, or black, it may be from an older bird.