HS 125 Series
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown
Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Runway
Flight Crew Took Evasive Action
Human Factors; Environment - Non Weather Related
After completing all required checklist and announcing our taxi out; our intention to takeoff on Runway 4 (twice) the PF (I was the PNF) and I performed a perfectly standard initial takeoff procedure; including (PF) announcing that the final was clear and the (PNF) announcing that the downfield looked clear.  During the takeoff we both notice a small bird on our direct takeoff path.  The bird passed by the aircraft with no incident or abnormal engine indication.  V1 was called and shortly there after the PF announced that he saw an aircraft on the runway and immediately started the aircraft rotation (slightly below Vr).  As the PNF I noticed the lower than normal speed and the aircraft on the runway in front of us; so I immediately lowered our flaps to 15 degrees to assist in the required takeoff lift.  We passed  over  the other aircraft; whom never announced their position (there was another aircraft inbound '10 miles out' that we both heard on the  radio clearly).  We performed a normal climbout and checklists without further incident.
HS 125 Captain reported noticing an aircraft on the same runway opposite direction during their takeoff roll at an uncontrolled airport. The Captain stated they rotated immediately after noticing the aircraft.