Steve,
Excellent.
You have noted 1/2 Bf 109 for Kaj Birksted. I have transcribed the combat reports for this and other victories of Kaj Birksted
http://www.danishww2pilots.dk/victories.php?id=3
http://www.danishww2pilots.dk/victories.php?id=4
The combat report suggests that they were both Fw 190.
On the other hand the 331 Sqn ORB suggests as you have noted one Fw 190 and one Bf 109.
http://www.danishww2pilots.dk/sorties.php?id=149
I have to admit, that I have not given this much thought myself before, but one could ask if one source is more reliable than the other.
Regards
Mikkel