Lloyd is totally right about the car gear vs field gear struggle. I've learned the hard way that a lens that feels okay in the shop feels like a literal brick after five miles. Tbh, you gotta be really careful about a few things that people often overlook when they're just chasing that extra reach.

• Watch out for lenses that extend a lot when zooming. They can act like a vacuum for dust and moisture if you're out in the elements.
• Be wary of balance. If the lens is super front-heavy, it'll kill your wrists even if the total weight seems fine on paper.
• Don't just trust every teleconverter. Sometimes they mess with the AF reliability so much that you end up missing the shot anyway. I would suggest really looking into how the weather sealing actually holds up in real-world messy conditions. I've seen too many people lose a day of shooting because of a little coastal mist getting where it shouldn't. Reliability is everything when you're miles from the trailhead...

Saved for later, ty!

I have spent significant time evaluating gear for field use, and my experience suggests you should be very cautious about the weight-to-reach ratio. I previously relied on a heavy zoom, but I eventually learned that physical fatigue during long hikes was negatively impacting my stability and shot count. You might want to consider whether a fixed focal length or a lighter zoom would better suit your endurance levels. Technically, the autofocus performance on these mirrorless bodies is heavily dependent on the maximum aperture. When I switched to my current setup, which has a more modest footprint, I noticed that the lighter weight allowed for much faster target acquisition. Be careful with lenses that have very slow apertures at the long end, as they can struggle in deep woods where songbirds often hide. I would suggest prioritizing a balance where the lens is light enough to hand-hold for extended periods without sacrificing the fast glass needed for dim environments. My current choice has fewer moving parts, which I have found to be much more reliable during trekking. It is definitely worth thinking about how much gear you are actually willing to carry when you are three miles from the car.

I am in the exact same boat, honestly. Spent the last few months trying to find a middle ground that doesnt leave me broke or in need of a chiropractor after a long day of hiking. I have tried many setups over the years and i always find that the heavier glass stays in the car more often than not. To add to the point above: I have been doing a ton of research comparing these two options for my own kit...

• Nikon NIKKOR Z 180-600mm f/5.6-6.3 VR: Great reach and the internal zoom is nice so it doesnt get all dusty, but man, it is a lot of weight to lug around for five miles.
• Nikon AF-S NIKKOR 500mm f/5.6E PF ED VR: Used with an adapter, this thing is surprisingly light and sharp as a tack, but it still costs a pretty penny even on the used market. I am still totally stuck on which way to go because I want that eagle-level reach without the back pain or the massive credit card bill. In my experience, you always end up compromising somewhere, and I just cant decide where to cut corners yet. TL;DR: basically stuck choosing between reach, weight, and price. Still havent pulled the trigger.

For your needs of photographing songbirds, shorebirds, and larger birds like herons and eagles with a Nikon Z-mount camera, while prioritizing reach, sharpness, fast autofocus, and considering weight for hiking, here are some recommended lenses:

1. Nikon NIKKOR Z 100-400mm f/4.5-5.6 VR S

   • Versatile zoom range ideal for bird photography
   • Sharp optics and effective vibration reduction (VR)
   • Fast and accurate autofocus
   • Relatively lightweight for its focal range at 1355g (3 lbs)

2. Nikon NIKKOR Z 400mm f/4.5 VR S

   • Prime lens with excellent reach for bird photography
   • Very sharp optics and effective VR
   • Fast and precise autofocus
   • Lighter than the 100-400mm at 1245g (2.75 lbs)

3. Nikon NIKKOR Z 180-600mm f/5.6-6.3 VR

   • Extensive zoom range covering a variety of bird photography situations
   • Sharp optics and effective VR
   • Fast and accurate autofocus
   • Heavier than the other options at 2000g (4.4 lbs) but offers more reach

4. Nikon NIKKOR Z 600mm f/6.3 VR S (if budget allows)

   • Extremely long reach for distant subjects like eagles
   • Exceptionally sharp optics and effective VR
   • Fast and precise autofocus
   • Relatively light for an 800mm lens at 2385g (5.25 lbs) but still hefty for hiking

Consider your specific needs, budget, and the types of birds you photograph most often when deciding between these options. The 100-400mm and 400mm lenses offer a good balance of reach, sharpness, autofocus speed, and weight for general bird photography while hiking. The 180-600mm provides more versatility and reach, while the 800mm excels for distant subjects but comes at a higher price and weight.