For birding, I am using a Z9 with 800PF almost all the time. I just ordered a Z8 to use as my second camera. For all you bird photographers what would be the most useful lens to use alongside the 800? 500PF (which I have), Z400 4.5, Z100-400 or F mount 600 F4 (which I have but would only use close to home due to size). The Z 400 and 600 TC's are out due to cost. I live in the Shenandoah Valley so most of the local birds are small and I'm rarely too close, but I do travel often so have opportunities for larger birds. I realize that if I"m on safari or whaling, I will need my 80-400 or a new Z100-400. If I didn't have the 500 the 400 4.5 would really interest me since I tend to prefer primes. What I'm looking for is a lens that would draw me away from the 800, which I love, so I'm not using it all the time. The combinations are interesting: 800 and a 400 to spit the focal lengths and have consistent controls on the lenses, 800 and 600 so I almost have a Z600TC, 800 and 100-400 in case a bear ambles by or a bird gets really close, along with consistent controls, or 800 and 500 for a lightweight duo. What second lens would get the most use?