Abstract: An irrigation sprinkler is provided having a nozzle and a flow control device for reducing fluid flow through the sprinkler when the nozzle is removed, such as might occur due to vandalism. The flow control device is coupled to the nozzle and is moveable between a first irrigating position and a second signaling position. In the first position, the sprinkler discharges fluid for irrigation. In the second position, the sprinkler discharges a reduced amount of fluid and signals that the nozzle has been removed and should be replaced. The flow control device also allows sufficient fluid flow for flushing debris out of the sprinkler when a flush cap is mounted to the sprinkler, instead of the nozzle.