>>4230311>400 is too short for birdsjoel sartore is one of the best wildlife photographers alive today
https://www.joelsartore.com/about-joel/common-questions/camera-equipment/his only lens longer than 400 is a massive $16000 prime. and he mostly uses dated bodies and it's extremely doubtful that he really needs the 15k fast 600. it's just very, very nice to have.
christina mittermeier is another such photographer
https://www.cristinamittermeier.com/faqher longest lens is 400mm and she uses dated "bad" sony bodies. she took THIS with a 70-200 f4 that some gearfags consider "almost unusably soft and slow". is that a bird? flying? and doing something INTERESTING besides existing? yes, it's a great photo.
these people are widely published and are paid to talk about taking photos.
gearfags have no clue. you do not "need" a 600mm, 800mm, 1000mm lens unless you are doing deep sky astro in which case you need something closer to a 2000mm constant f11.... telescope. you need to git gud.