What kind of camera by Canon is best for bird photos

[ws]

I like to go birding and found it enjoyable using my sons Canon 5T, some pics were good and others I needed sharper resolution. Would an EOS 70 D be marked improvement? Is this model restricted to specific lenses, so if are there restrictions to the lenses it can use?

[TTMartin]

EF-S 55-250mm f/4-5.6 IS STM Refurbished

[TCampbell]

For birds-in-flight, a camera with a fast continuous burst speed and a good buffer size will help.  

A 70D would be an upgrade... a 7D II would be an even better upgrade (much better focus system, faster burst speed, etc.) 

The other consideration is the lens.  While it's nice to have a 600mm lens to capture shots, the angle of view through a 600mm lens is very narrow.  So if the bird goes out of frame (and it will) you'll have a hard time re-acquiring your target.  So it's NICE to have a zoom that lets you drop the focal length to an angle of view that isn't so tight... find and re-center your subject, and then zoom back in to focus and shoot.

There are a couple of 150-600mm lenses on the market (by Tamron and Sigma -- neither of which I have any experience using so I wont bother to comment or recommend a particular lens.)  Canon makes the 100-400mm lenses but in longer focal lengths the zooms tend to get very expensive (the 200-400mm with builting 1.4x extender is the longest "zoom" they make and the rest of the super-telephoto lenses are primes.)  The Tamron and Sigma 150-600mm lenses seem to be popular among the birding photography crowd.

[ebiggs1]

Almost always the better lens is the best solution. All the lens you are considering are poor for what you want.
A 70D is not going to have a great deal better sensor than the T5 has. It does have better AF no doubt.
If it was I, I would buy a lens like the Tamron 150-600mm super tele first. Learn to use it and later get the 70D. If you truly love this hobby maybe consider the 7D Mk II. It is a absolutely fantastic camera upgrade over the 70D and vastly better than the T5.

[ebiggs1]

BTW, I would get up close and personal with a good post editing program. Like Photoshop Elements. That will impact your photos more than anything.