A long$-$term study on cliff swallows $-$ a type of songbird that catches insects in flight and nests in large colonies under bridges $-$ found that the wing length of the population decreased by about $6$ mm over several decades. This occurred because birds with shorter wings can maneuver and change direct faster, leading to shorter$-$winged birds getting killed by traffic less often. This is an example of:

stabilizing selection

directional selection

sexual selection

disruptive selection