Photoshop :: Unable To Get Edges Right

I've been using Photoshop CS5 to edit my photography for a while but have never bothered with masks until just recently. I watched this video and figured it would be fairly easy but I'm still having quite a bit of trouble getting results that look even halfway decent; I can never get the edges right. I've tried playing around with all the "Refine Edge" settings but nothing really makes it look realistic and un-manipulated, so I figured I'd ask here in case I'm missing something or doing something wrong.

To start out with I figured I'd try replacing the background of one of my photos with the background in another one of my photos, in this case some snowy branches. Here's a screen shot of the original photo (with the birds/foreground roughly selected with the Quick Selection tool):

And here it is after making that selection into a mask:

As you can see, some big chunks of three of the birds are missing and the edges are pretty obvious in a lot of spots. This is ultimately what I'm trying to fix.

A bit off topic, but also problematic are the gaps around the birds' legs where the red in the background shows through...not exactly sure what to do about those. In addition, I find the stripped, broken end of the branch sticking up in the middle of the picture to be a pretty big eyesore but haven't found a convincing way of removing it.

Anyway, here's a closer look at the edges:

When I check "Smart Radius" and increase the Radius size to about 40 pixels I get something resembling this:

...which is not really an improvement over the original IMO. I also tried painting in the radius manually along the edges of the bird's head using the Refine Radius tool but this only created more fuzziness around the edges. Increasing the "Shift Edge" value created even more fuzz. Using the Erase Refinements tool made the edges too sharp and bits of the bird started disappearing again, making it look similar to how it was originally.

Here's another example of the same thing on the outline of the third bird in the picture:

How it looked originally and...

...how it looked after messing around with the radius/refine radius tool. It's a slight improvement over the original but bits of the bird are still missing and there's that fuzz around the edges that I don't know how to get rid of.

By the way, here's a download link to the full-size original two photos in a zip file: Background and Foreground.zip