I also had such an idea, but instead of a steel bar, use a pointed steel corner (a steel corner bar has a resistance area in the ground per perpendicular force applied to it that is several times higher than that of a bar reinforcement). Bells can be attached directly to the cord approximately in the center. If the base line rope is not very elastic (perhaps in other countries the bird is many times larger and it makes sense to use a very thin steel cable. For example, such as partridge or pheasant), then a tension spring should be used at one end of such a steel cable. That is, there is room for further technical creativity to modernize the trap.