[plank]

The point the story tries to make is that the Hawk learned traffic signals. That is not necessarily the case. It could be that the hawk just sees that the cars are blocking the sight of the prey.

Still an intelligent action, only does not mean the hawk understands the signal itself.

[hatthew]

The suggestion is that the hawk hears the signal and knows that the line of cars is about to be unusually long in a minute, so it prepares by flying into position.

[happyopossum]

the story as told outlines that the hawk will stage itself when it hears the sound of the crosswalk, in anticipation of the line of traffic getting long enough for it to use as concealment.