I probably have a thousand bird images just posted here on the forum, although not so much in the last year. If you are used to the 8 FPS-23 shot buffer of the K-3 then the K-1 can be really irritating. The buffer fills to quickly and the time it takes to clear the buffer and get the camera back on line is too long. The K-3 is a much more satisfying camera for that purpose. Not to mention that you get better detail in the crop area with a K-3 if you end up just using crop.
In terms of IQ, I did a few shots at some point to see if people could tell the difference between K-1 images and K-3 images... they couldn't.
There are times I go out and use the K-1 in the blind, just because I can. But it is often an unsatisfactory experience.
Hey, there are 497 images
in this folder... but hey, I'm not a serious bird photographer. Also check out Kengoh's work. And
https://www.pentaxforums.com/forums/122-lens-clubs/55946-300mm-plus-lens-clu...ng-lenses.html
Top of the list here.
So nothing wrong with the K-1 as a birding camera, but ti's a pretty straight trade off, it takes a little more skill and with the slow frame rate, probably less chance of getting exactly the pose you wish, but, it's a better image if you get it. And I find absolute quality in terms of resolution and DR are rarely issues in birding.
A K-3 image
A K-1 image
A K-3 image
You can get the job done with either. It's easier with a k-3. But, I use both depending on my mood. Sometimes I need the low light performance of the K-1, and I feel lucky.
Just clicking through my images, and without quantifying them, my feeling is most ( but definitely not all) of the shots that stand out since I bought the K-1 have been K-1 images, even though I have a lot more K-3 images.
The detail difference between the two Dark Eyed Junco images is pretty representative. But a bit misleading in that the K-3 Junco is twice the distance away, and for detail, closer is always better.
In conclusion , K-1 for birding is not the best capture option, but, it's a very good IQ option if you're skilled enough to capture with it.
For wildlife, it's a wonderful camera.
Especially for images like this where you want detail on the subject, but some context as to the environmental living conditions of the animal.
You do however have to invest in longer glass...
I bought my Tamron 300 2.8 and TCs to increase my reach with the K-1. But guess what happened, I still get even more reach with my K-3 using the same combos. It quickly became my goto birding lens on both cameras.