2 ACCEPTED SOLUTIONS
While on the subject, a good sturdy tripod is always good such as the Manfroto Pro190. And of course the post processing software of which Photoshop is the best. There are others but none in the same calss as PS..
If I had used my tripod on the hummingbirds, I could have gotten a much better, sharper photo. But hummingbirds are quick and like I say are difficult to capture.
Here I am on a recent Senior Photo shoot. One of the Mom's caught this on her cell and thought it cool to stick me on her Facebook. Oh, my! 
Sheila,
It certainly looks like a Canon 100-400mm f4.5-5.6 L IS USM is in your future. You blog site is really nice and you are coming along. Canon does make a 400mm f5.6 non-IS prime lens and it may be a consideration for you. One thing you will find out is most of the shots taken from a zoom lens, occur at the long end. Not all but most! It does not have IS but is a very nice lens that is cheaper and lighter than the 100-400mm zoom.
You wanted some pictures? Here are a couple of a male hummingbird taken with my 100-400mm Canon at the 400mm end. Hummingbirds are one of the more difficult birds to capture.
These were handheld on my 7D with the 100-400mm.
While on the subject, a good sturdy tripod is always good such as the Manfroto Pro190. And of course the post processing software of which Photoshop is the best. There are others but none in the same calss as PS..
If I had used my tripod on the hummingbirds, I could have gotten a much better, sharper photo. But hummingbirds are quick and like I say are difficult to capture.
Here I am on a recent Senior Photo shoot. One of the Mom's caught this on her cell and thought it cool to stick me on her Facebook. Oh, my!
"I very nice shot of you; I like it! That is a big lens!!
Us seniors sure know how to have a good time!!"
Um, actually that appears to be a 70-200mm. For birders, wildlife and sports shooters, that would be a fairly moderate or medium sized lens 
If you are looking at a longer lens for nature & wildlife shooting, how large and heavy are you willing to carry around? There have been some good suggestions above, but not much mention that you are looking at relatively large and heavy lenses. You may want to go look at any you are considering in a store... Don't buy without seeing and handling, to be sure you are willing to haul it around.
You'll have to decide for yourself how long a focal length to get. Most birders say there's no such thing as a "long enough" lens. But you have to balance that against size, weight and cost considerations. Also, longer telephotos, even those with stabilization, can be more difficult to shoot with. A monopod or tripod might be needed with a longer tele. And shooting more distant subjects with a longer lens through more atmosphere comes with other potential problems, due to haze and other atmospheric effects.
You'll have to find a balance that works for you... something long enough to serve well most of the time, but manageable.
The Canon 100-400L IS is slightly larger than a Canon 70-200/2.8. It's got a tripod mounting ring, but is a push/pull zoom design, which particularly lends itself to fast handheld use.
Sigma 120-400 OS is about the same size & weight (but about $500 less expensive). It also has a tripod mount, but is a more traditional two ring zoom design.
Sigma 150-500 OS is larger and heavier than either of the above (and roughly $400 less expensive than the Canon), with a tripod mount and traditional two ring zoom design.
Sigma 50-500 OS is really big and heavy.... it's nickname is the "Bigma", after all. It's about the same price as the Canon 100-400.
Sigma 50-150/2.8 OS a bit baffling. It's a very nice lens, no doubt. But it's just as large and heavy as a 70-200/2.8. The 50-150mm just gives less reach... Plus it can only be used on crop sensor cameras (such as your T3 and 70D), while all the 70-200s can be used on both crop and FF cameras. Usually an advantage of crop-only lenses, especially shorter focal lengths, is a more compact, lighter weight lens. It is a little lower cost, but the 50-150mm sort of makes me wonder why bother? Why not just get a 70-200/2.8 that can be used on both crop and full frame cameras? By the time you add a 1.4X teleconverter/extender to the 50-150mm, the combo will end up costing more and be larger, heavier than a 70-200mm. And the lens/TC combo is almost certain to give lower image quality than the longer zoom alone.
Generally speaking, for best image quality it's best to avoid using teleconverters with zoom lenses. If you must, be sure it's a good quality and try to get by with a weaker 1.4X teleconverter. A stronger 2X TC always has more effect on image quality. A 1.4X on a 50-150mm lens makes for an effective 70-210mm combo... So I am back again to asking why not just get a 70-200/2.8 instead? Or, for wildlife and small subjects, an even longer lens such as those mentioned above and below.
Not that I have anything against teleconverters. One of my favorite portable/handheld setups is Canon EF 300mm f4L IS lens with and without 1.4X teleconverter (Canon EF 1.4X II). This gives me two useful focal lengths, with stabilization and in a reasonably compact, handholdable size. Here is a shot made with the 300mm + 1.4X, on a 5D Mark II camera (full frame)...
This is the same lens and TC combo, on 7D (crop sensor, similar to your 70D)....
This was done with the lens alone, on 5D Mk II....
And this was done with the 300/4 IS alone on 7D...
It is very fast focusing and, as a bonus, the EF 300/4 IS is the closest focusing of Canon's prime lenses longer than 200mm. This is cropped slightly, but gives you some idea of the near-macro capabilities of the lens...
The 300/4L IS is only slightly larger than and about the same weight as a 70-200/2.8.
There are more compact & lighter lenses, such as the Canon EF 70-300mm DO. A friend uses one of those and is quite happy with it. It won't take a teleconverter, but gives pretty good reach all on it's own, is fast focusing and has very good image quality.
The Canon EF 70-300L IS is another top notch lens in all respects, but fairly large and heavy.
A lens very popular with birders is the Canon EF 400mm f4.6L. This isn't a lot larger or heavier than the 300/4 IS, and is fairly affordable. It's also quite sharp and fast focusing. The main drawback, in my opinion, is that it lacks IS. If you keep your shutter speeds up, it can be used handheld. But if light is low it might be challenging to shoot handheld at less than 1/500 (on a crop camera). Also, it's just a single focal length... doesn't have the versatility of a zoom or the 300mm + 1.4X combo.
Regarding DXO Mark website... Sure... look there. But don't put too much weight on what you read. It's just a resolution test, and there is a lot more to lenses than a lab test alone can reveal. They test a single copy of a lens. If you look at other websites such as Lensrentals.com, where they test multiple copies of any given lens (they buy them in the dozens, for their rental business, and test them after each return), you'll find copy variation. Looking at the "top 6 places" on DXO could be completely meaningless, they are all so close to each other. If they were to test additional sets of those lenses, copy variation might change their rankings around completely. And, if you do some searching you'll find some people have doubts about the testing methods there. Still, it's useful... Just take the info there with a grain of salt.
Have fun shopping!
***********
Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & PRINTROOM
"... but the 50-150mm sort of makes me wonder why bother? ..."
The answer is a simple one, my friend, as it provides crop body users the same look and feel as the 70-200mm does for FF owners.
For some reason the 70-200mm combo has been a highly popular range for a zoom. I have one on my 7D and I can emphatically say the Sigma 50-150mm f2.8 DC HSM OS is a fantastic lens. In fact it is the lens that began to change my mind on third party lenses especially Sigma. I now have 6 Sigma lenses and 6 months ago I wouldn't have taken one as a gift!
I still deplore off brand lenses but I must admit they are making some strides in quality and performance.
There won't be any Tokina's and most likely no Tamron's but the Tammy 24-70mm f2.8 is perking my interest. So who knows.....................?
