Just a few additional comments here
My observation about MFD comes from using the K300/4 which is limited to just under 4 meters, I agree the DA300/4 is somewhat less restrictive in that respect. But having said that, 3-4 meters is a good distance, and is also a distance where the 1.7x AF TC can get the image a lot bigger in the frame. While not intending to offer "competing images" in this thread, here is what can be achieved at 3-4 meters using the 1.7x AF TC along with the K300 / 4

this has been used as an example in many posts because it illustrates a lot of things.
This shot was taken using flash, which you shold also consider when photographing birds. I know the High ISO capabilities of the cameras have improved greatly since I took this with my *istD, but flash offers another thing, specifically the ability to freeze the image.
With respect to the birds in flight, someone pointed out the shutter speed was too low and that the shots relied on SR. When shooting BIF, I find SR can also add blurr, because the subject is moving and SR cannot distinguish the lateral movement from deliberate panning. THe shot with the gull at much higher shutter speed is a good illustration of this.
Keep at it you are making great improvements in a very short time. Small birds like your robin (or my chickadee) are actually the hardest thing to photograph because they are very very small. It is relitively easy (some exceptions excluded) to get a shot of a bird that is 500mm long, compared to one that is less than 100mm.