In America, haggard merlins do ring quarry as part of their repertoire. Furthermore, as Ray points out- many catches are made in the air during ringing flights, either at a high pitch or on the way down as both are stooping back to the ground. That is true for wild merlins as well as falconry birds.

My experiences with eyas merlins and high ringing flights in open country do not jive with what Jim is saying. Young merlins pursuing that quarry will engage in high ringing flights within a few attempts, naturally, without any "training". The young merlins have to be flying hard and learning how to foot that quarry very early in the year - and if they are going to be successful, they have to develop in lock-step with the quarry as it becomes tougher by the day in early fall (youngsters maturing and adults becoming full-summed in their flight feathers). Taking that much time (any time for that matter) away from actually flying at quarry at that time of year will put the young merlin behind, developmentally, and the game will be up. That's my experience anyway. Of course I am talking about house sparrows out in the open desert grasslands.

But who knows, I'm not much of a bird trainer in any respect.