Regarding what #1 said about the light, they are totally right... those deep woods can be a real challenge! I honestly think the R7 is a fantastic choice for your trip tho, the autofocus is just amazing! Since you want to keep it under $2100, the most reliable and methodical approach would be to look at the Canon EF 100-400mm f/4.5-5.6L IS II USM on the used market. It is a legendary lens and the image quality is honestly fantastic. Even though its heavy, the f/5.6 aperture is a lifesaver in the shade compared to the f/8 on the cheaper RF. Plus, you avoid all those weird pulsing issues that plague adapted Sigma glass on the R7... safety first when you're on a big trip! If you really want to go native and maximize your reach, you should check out the Canon RF 200-800mm f/6.3-9 IS USM. It fits right in your budget at about $1899 and the reach is just incredible for birding! I love how fast it focuses. To handle the slow aperture in the Olympic Peninsula forests, you can just use Topaz Photo AI to clean up the high ISO noise later. It works like magic, basically. This way you get a modern, native lens that is much lighter than the old EF setups. It is a fantastic middle ground that keeps your wife happy and your shots sharp!

Honestly, after shooting birds for over fifteen years, gear transitions are something I've dealt with plenty. The R7 is a beast, but you're right to be wary of that f/8 in the Olympic Peninsula... those forests are basically dark rooms even at noon.

• Skip the Sigma. In my experience, the pulsing issue on the Sigma 150-600mm f/5-6.3 DG OS HSM Contemporary is a total dealbreaker for high-speed stuff. It just hunts way too much.
• Go for a used Canon EF 100-400mm f/4.5-5.6L IS II USM. It's built like a tank and handles the R7 autofocus perfectly with the Canon Mount Adapter EF-EOS R. You can find them used for around $1300 easily.
• The Canon RF 100-400mm f/5.6-8 IS USM is way too dark for deep woods. I love how light it is, but you'll be pushing ISO 6400+ just to get a decent shutter speed under the canopy. That EF II lens is heavy, but ngl, the image quality and focus speed are worth the extra weight for a big trip like that.

Regarding what #1 said about the light, they are totally spot on about those forests being dark as a cave! I remember being out in similar woods a few years back and my gear just kept hunting because there wasnt enough contrast for the sensor to grab onto... it was honestly a nightmare! You really want something that you can trust implicitly when a rare bird finally pops out of the shadows. Reliability is the big one for me because there is nothing worse than hiking five miles just to have your autofocus start pulsing right when the action happens. I have spent way too much money on gear that failed in the field, so I am all about what actually works when you are tired and muddy! Just curious tho, how much weight are you actually willing to carry on those 5-mile hikes? Like, is a heavy setup a total dealbreaker if it means better shots? And are you aiming for tiny songbirds or are you mostly after the big stuff like elk and eagles?

Just a quick warning before you commit. You might want to be really careful about third-party glass like Sigma or Tamron on these new mirrorless bodies. Even with the adapter, the autofocus communication can be a bit flaky compared to native glass, and when you are out in the field, you want something you can trust 100 percent. I would suggest staying away from the non-L series lenses if you are actually going into the deep brush. The Canon RF 100-400mm f/5.6-8 IS USM is a decent lens for the price, but it has zero weather sealing. In a place like the Olympic Peninsula, moisture is a real gear killer. Plus, that f/8 aperture is going to force your ISO way up, and honestly, the R7 files get pretty crunchy once you start pushing the gain to make up for lack of light. Its better to have a lens that works every time than one that struggles the moment the clouds roll in.

Building on the earlier suggestion, everyone here has really hit the nail on the head regarding the lighting challenges you are gonna face up there... especially since the R7 sensor is so dense and can get a bit noisy if you arent careful with your exposure. It seems like the main points of the discussion so far are:

• The native f/8 aperture might be pushing it in the deep timber during overcast days.
• Third-party autofocus pulsing is a massive headache for the newer R-series bodies.
• Weight is a huge factor if you are actually hiking five miles into the brush. Honestly, this whole budget vs weight debate reminds me of my first big trip out to the Hoh Rainforest years ago. I was so obsessed with having the perfect setup that I spent three weeks researching gear just like you are doing now. My brother-in-law actually ended up coming with me and he brought this ancient film camera his dad gave him. We hiked about four miles in before he realized he had forgotten to actually put a roll of film in the thing. We spent the whole afternoon looking for an elk he thought he saw, and every time I stopped to swap out my glass or check my settings, he was just standing there pretending to take photos so he wouldnt feel left out. We ended up getting caught in a literal downpour and had to hide under a cedar tree for two hours. By the time we got back to the truck, my boots were so soaked they weighed more than my actual gear bag... it was a total mess, but those trees were gorgeous even if I barely got a single sharp shot because of the fog.