Metal Casting Zone

Last week I did two tries to cast a cast iron bird ornament (the original whch used as pattern is also cast iron, bottom on photo).
The photo shows two castings including the sprues (top). What I noted is the fluidity of the iron: it fills even the narrow air vents, so the casting temperature (ca 1300oC) or fluidity is not an issue.
BUT:
the fine details on the surface are lost. I suspect the entry on the 'back' of the bird which allows a strong flow of the metal.
The mold is water+oil based sand and some talcum powder is put on the pattern and the mold halves to allow separation of the pattern after molding.

Does anybody know what can be the problem ?
The size is about 8cm long for the bird and the entry sprue about 8mm diameter.

Is the detailed surface facing upward when poured? maybe some air pressure prevents filling completly? If that is the case i might flip it. does the detail on the back seem right?

Im looking at it and it looks like he tried it both ways, the only thing I can think of is more head pressure needed.....???????

Hi Hottestfurnace
I was thinking along the same lines as aonemarine ,that sprue is very small diameter restricting the feed to the casting cavity. Johncast

True, that is probably the problem I used a 6mm drill bit to 'drill' the sprue in the packed sand.
Thanks all, I'll try again.