Question: Which ethnicity was the pilot, who is credited with 258 aerial victories flying the Jagdgeschwader 54, identified as?

Context paragraphs:
Cosimo Rennella: Lieutenant Colonel Cosimo Rennella Barbatto was an Ecuadorian World War I flying ace of Italian heritage.  He was credited with seven confirmed aerial victories flying for Italian aviation during the war; however, his pioneering civil aviation activities both before and immediately following the war were probably even more important than his martial career.

List of World War II aces from Germany: This is a list of fighter aces in World War II from Germany.  A flying ace or fighter ace is a military aviator credited with shooting down five or more enemy aircraft during aerial combat.  German day and night fighter pilots claimed roughly 70,000 aerial victories during World War II, 25,000 over British or American and 45,000 over Russian flown aircraft.  103 German fighter pilots shot down more than 100 enemy aircraft for a total of roughly 15,400 aerial victories.  Roughly a further 360 pilots claimed between 40 and 100 aerial victories for round about 21,000 victories.  Another 500 fighter pilots claimed between 20 and 40 victories for a total of 15,000 victories.  It is relatively certain that 2,500 German fighter pilots attained ace status, having achieved at least 5 aerial victories.  These achievements were honored with 453 German day and "Zerstörer" (destroyer) pilots having received the Knight's Cross of the Iron Cross.  85 night fighter pilots, including 14 crew members, were awarded the Knight's Cross of the Iron Cross.

List of German World War II night fighter aces: A flying ace or fighter ace is a military aviator credited with shooting down five or more enemy aircraft during aerial combat.  German day and night fighter pilots claimed roughly 70,000 aerial victories during World War II, 25,000 over British or American and 45,000 over Soviet flown aircraft.  103 German fighter pilots shot down more than 100 enemy aircraft for a total of roughly 15,400 aerial victories.  Roughly a further 360 pilots claimed between 40 and 100 aerial victories for round about 21,000 victories.  Another 500 fighter pilots claimed between 20 and 40 victories for a total of 15,000 victories.  According to Obermeier, it is relatively certain, that 2,500 German fighter pilots attained ace status, having achieved at least 5 aerial victories.  453 German day and "Zerstörer" (destroyer) pilots received the Knight's Cross of the Iron Cross.  85 night fighter pilots, including 14 crew members, were awarded the Knight's Cross of the Iron Cross.  The list is sorted by the number of aerial victories claimed at night.

Victor Fyodorov: Lieutenant Viktor Georgiyevich Fyodorov (11 November 1885 - 4 March 1922) was a Russian World War I flying ace credited with five aerial victories while flying with the French military air service.  Having left Russia for Belgium in 1908, with a further move to France, Fyodorov was still living in the latter when World War I began.  On 21 August 1914, he volunteered for the French Foreign Legion, and served with them until wounded and invalided from infantry service.  After preliminary duty as a chauffeur, he became a pilot on 27 November 1915.  After acquiring Pierre Lanero as his mechanic, aerial observer, and gunner, Fyodorov scored three aerial victories in March 1916 with Lanero manning the Caudron's guns.

Kurt Welter: Kurt Welter (25 February 1916 – 7 March 1949) was a German "Luftwaffe" fighter ace and the most successful "Jet Expert" of World War II.  A flying ace or fighter ace is a military aviator credited with shooting down five or more enemy aircraft during aerial combat.  He claimed a total of 63 aerial victories—that is, 63 aerial combat encounters resulting in the destruction of the enemy aircraft—achieved in 93 combat missions.  He recorded 56 victories at night, including 33 Mosquitos, and scored more aerial victories from a jet fighter aircraft than anyone else in World War II and possibly in aviation history.  However this score is a matter of controversy; research of Royal Air Force losses suggests Welter overclaimed Mosquito victories considerably.

Jagdgeschwader 54: "Jagdgeschwader" 54 (JG 54) was a Luftwaffe fighter wing during the Second World War, which was the second highest scoring wing of all time, JG 52 being the highest.  JG 54 flew on the Eastern Front claiming over 9,600 aircraft shot down, with pilots such as Walter Nowotny, Otto Kittel, Hans-Ekkehard Bob, Max-Hellmuth Ostermann and Hannes Trautloft being termed "Experten".

Les Holden: Leslie Hubert (Les) Holden, MC, AFC (6 March 1895 – 18 September 1932) was an Australian fighter ace of World War I and later a commercial aviator.  A South Australian, he joined the Light Horse in May 1915, serving in Egypt and France.  In December 1916, he volunteered for the Australian Flying Corps and qualified as a pilot.  As a member of No. 2 Squadron on the Western Front, he gained the sobriquets "Lucky Les" and "the homing pigeon" after a series of incidents that saw him limping back to base in bullet-riddled aircraft.  He was awarded the Military Cross, and went on to achieve five aerial victories flying Airco DH.5s and Royal Aircraft Factory S.E.5s.

Hubertus von Bonin: Hubertus von Bonin (born 3 August 1911, Potsdam – 15 December 1943) was a German Second World War fighter ace who served in the "Luftwaffe".  A flying or fighter ace is a military aviator credited with shooting down five or more enemy aircraft during aerial combat.  Bonin is credited with shooting down 77 enemy aircraft.  The majority of his victories were claimed over the Eastern Front.  He also claimed four victories in Spain during the civil war.  His commands included "Geschwaderkommodore" of Jagdgeschwader 54 (JG 54—54th Fighter Wing).

Walter Nowotny: Walter Nowotny (7 December 1920 – 8 November 1944) was an Austrian-born fighter ace of the Luftwaffe in World War II.  He is credited with 258 aerial victories—that is, 258 aerial combat encounters resulting in the destruction of the enemy aircraft—in 442 combat missions.  Nowotny achieved 255 of these victories on the Eastern Front and three while flying one of the first jet fighters, the Messerschmitt Me 262, in the Defense of the Reich.  He scored most of his victories in the Focke-Wulf Fw 190, and approximately 50 in the Messerschmitt Bf 109.

Kirill A. Yevstigneyev: Guards' Captain (later Major-General) Kirill Alekseyevich Yevstigneyev (Russian: Кирилл Алексеевич Евстигнеев ) (17 February [O.S. 4 February] 1917 – 29 August 1996) was a Soviet fighter pilot and one of the top Soviet aces of World War II.  During his career he claimed 56 aerial victories flying the Lavochkin La-5 and La-7 fighter.

Supporting paragraphs: Jagdgeschwader 54 Walter Nowotny
Answer: Austrian-born