A system for positioning crop windrow guide shields projecting generally rearwardly alongside the crop discharge stream as it exits an agricultural mower. The shields are coupled for simultaneous, coordinated movement and repositioned by a powered actuator in response to either a manual input by a vehicle operator or automatically by a controller based on a steering angle deflection between a tractor and a towed implement. The system may be adapted for use with a single implement being operated on a side hill to control windrow drifting. The system may also be used with simultaneously operated front-mounted and pull-behind mowers to direct the crop discharge streams into a merged windrow.
