Advice needed on camera upgrade path.

A short history, I sold my Canon 60D years ago for a smaller kit. I currently run the Lumix fz1000 and seriously thinking about getting a DSLR again.
I still have some older Canon lenses first being the EFS 18-55 and second is the EFS 55-250, I was thinking about moving over to Nikon but since I have these lenses Canon is the path.
The question.
Which body should I look for?
Main use would be birding.
Cameras I'm looking at currently are the
6D Mark ll
80d
t8i/850D

under 1k budget and I've looking at MPB.com and Canon refurd and Unique Photo used.

Thanks in advance

Since you are a birder, the APS-C body would provide you with 'reach' advantage (frame filling). Canon mirrorless are mostly out of your price reach, and most are FF, not APS-C.
A recent post by TeamSpeed does you a favor in some very well priced options for you!
https://photography-on-the.net …showthread.php?​p=19509145

This chart will assist you to see the density of pixels-per-millimeter of sensor, more is better for birders

Those lenses won't work on FF so they are no justification for getting a 6Dii.

The 18-55 is worthless as there're about a billion of them in circulation, and a 55-250 sold here recently for $100. Bottom line is there isn't much value there that would drive the decision toward Canon. Sure, you have them... that's value, but only if you look at it a certain way and even then it only supports a move to Canon APS-C.

Don't get me wrong... I'm a Canon fan. And from that perspective the 80D or even 90D look good. It's just that you'll probably want longer glass at some point so you will then not be using either of those lenses anyway.

I hear ya, back when I had the 60D I also the Sigma 150-500. I sold them both to downsize

What about the 7D Mark ll?

I like mine. They're pretty cheap these days but it doesn't quite have the crazy pixel density of the 90D. For BIF, though, it might be better than the others due to the sophisticated AF.

When you say birding, do you mean BIF or static subjects?

6d or any ff EOS is not going to get efs lens mounted, if I'm not mistaken.
I have efs and ff, but I'm reluctant to try it again

250 at the end is not really for birding. I have and had -200 on crop, and it is only good at birds feeders on the porch.

Canon AF in servo is really good, I have no problems with 500d for birding and 70-200 F4 with cheap vivitar's x2. But still not enough reach often.

I never used op listed sites for camera and lenses. Local classifieds, Potn for sale and eBay.
Just have to be sure seller is real and pay by PayPal.

Mirrorless FF EOS accepts efs as a point of clarification.

I have the T8i and have been quite happy with it. I have used it with the EF 100-400L II and a 1.4x TC and been happy with the bird images

The 7DmkII is a great camera (I use one). 20mp should be enough unless you print often and print LARGE - even if you crop moderately.
My R5 in crop mode has less MPs than that and I use crop mode considerably when birding.

As a birder, save your future $$$s for longer glass.

If you're going to use it only for birding, consider getting an R10 and RF 600mm f/11 STM. You will exceed your budget slightly but if you have time you may be able to get them on sale (I picked up the 600mm for $400 on Canon's refurb site).

If you get just the R10 for now, at least you'll be ready for whatever new RF lenses will come in the future.

TeamSpeed wrote in post #19510053
Mirrorless FF EOS accepts efs as a point of clarification.

...unfortunately, for the OP area of photographic interest, even the R5 does not equal a 12 year old Rebel in pixel density!

However if pixel density of a 40D is enough, a 55-250 STM works pretty well from a lightweight and cheap telephoto option for the R series.

The 7d2 is an excellent camera. Id consider it with a 400mm 5.6?L. You can probably find both fairly cheap but maybe a tad over budget but it will be a really high quality setup that is surprisingly light

Maybe add a monopod for stability since the 400 does not have IS.

I understand where you're coming from. What's equivalent to the 7d M lol in Nikon let's say or other makes?