Been doing a couple more of these crazy birds out of junk.
I like to recycle some bits of circular saw blade for the wings as in the second photo. After all, the teeth are already shaped like wing tips. Problem is, the spot welding is easy with the mig, but it takes very little pressure on the wings for them to break off. The weld is secure but it breaks just next to the weld. I guess saw blades are very high tensile stuff.
I haven't tried annealing the blades but perhaps that is the way to go. Any ideas?

 

if you have a a/c-o/x torch heat welding spot to red then weld that should work

yes sound like a hardness problem

IronWolf is right on, Your not getting any penetration, Got to preheat especially with mig, It will just lay on the surface.Your birds really look nice Ausfire!

                                                                                                   Ironmike

So I preheat to red the area of the saw blade to be welded and weld it with mig while it's red hot? Sounds like a plan.

I have overcome this problem by firstly doing a high amp weld on each of the parts first at the point they will be welded together only then welding the two pieces together With a third weld

Thanks Andrew. Worth a try. Those saw blades are pretty thin so I'm always careful not to blow them away. They do make good wings though. And rooster combs.

I agree with all of the above, but in cases where all else fails I find tig welding with silicon bronze filler rod holds up.