Doobie,
That's a pretty danged good shot actually!
I also have a Xsi and a 55-250mm, it's a pretty good lens, not the greatest birding lens though, but for an all-around lens, it's pretty good quality.
(I rarely, if ever use my 55-250 though since I got a larger lens, but I still like it)
You have it perfectly focused on his eye, that's for sure!
What I would suggest is, (of course get in as close as possible) look up the "Rule of thirds" on Google and see what that's about, it'll help you out in cropping in camera, or, post=processing...
I would've also tried to move around to where that tree trunk wasn't in the shot so much, if you could, sometimes I know it's not possible, the cropped image doesn't look so noticeable though.
Try not to shoot when the sun's so high in the sky, it makes for unflattering shots, but I know, we can't always pass up a shot when we see it, but 'just in case'! heh
The background has a lot of noise, along with your camera, you should've gotten a CD that had Digital Photo Professional (DPP) on it, that has options that can help that, especially if you shoot in RAW.
If you don't shoot in RAW, please check that out also, you'll really be glad you did, you can do a whole lot more to save bad images, and all kinds of things using it.
(.jpegs just don't have as much information in 'em)
If you already know this, then maybe someone else can benefit, I don't mean to go on, but I did... heh
If you plan on shooting more birds, definitely consider a longer lens, look at what other here have and after a while you'll 'get it', if you don't already.
It took me a while to "get it", but when I did, I knew that I couldn't use my 55-250mm anymore and expect shots like they were getting.
Now that I do have a longer lens, I still have trouble, but it's not the lens's fault. heheh
This is not a 'have to' thing, but most here think along those lines.
Anyway, maybe this'll help some... Nice shot though!
Randy