A forestry tree felling head (4) is disclosed. The head is configured for processing multiple stems (50, 51) at a time, in which stems may be fed through the head independently from each other, to automatically align them before bucking. The head has a frame with a feed axis and a drive system (11a-b, 12a-b) configured to position a first stem on a first side of the feed axis and a second stem on a second side of the feed axis. A first end sensor (17a) having a first sensing region (52a) extending into the first side of the feed axis is configured to output a signal indicative of the presence of an end of the first stem within the first sensing region. A second end sensor (17b) having a second sensing region (52b) extending into the second side of the feed axis is configured to output a signal indicative of the presence of an end of the second stem within the second sensing region. A controller is fed these signals and independently operated feed rollers of the drive system adjust the stems such that their ends substantially align to be cut by the cutter (15).
