>>4311356Most decent bird photographers actually use 400mm on FF with great success. Ultra long lengths are for small birds sitting on branches specifically.
>>4311317I strongly recommend against buying budget canon RF gear, as you'll then be stuck with the RF system. You're near the price of used sony but canon includes no semblance of weather sealing on anything that is not a pro body (r1, r3, r5, r6, r7) or an L lens. The R10 doesn't even have IBIS.
Instead, put EF L lenses on a used pro body (r7/FF r6) or a newer canon DSLR, or save a buck and go to FF or APS-C sony mirrorless. The a6700 is well made and r7 tier, and can use dirt cheap, weather sealed, tack sharp lenses from sigma and tamron. Just avoid RF entirely if you value your sanity and happiness in the long term. It's a premium system actually intended to be purchased by employers, not hobbyists and freelancers, hence the brutal stratification with missing weather sealing and IBIS.
EF lenses are great, because they can migrate to any mirrorless system. They are the most widely supported lenses on earth and buying a top tier EF L lens costs as much as buying a budget RF lens made of plastic and lacking real weather sealing. RF? It's the most anti-consumer lens system on earth.
