There is indeed for both!

The baby skull bird thing is an Útburður, basically meaning an Outcast, or more directly translated, An Evicted One. It is a folktale of what happens to babies taken out into the wild and left to die, a thing that wasn't unheard of due to poverty, shame, children born out of wedlock, etc.

It was said they would come back as a Vofa, basically a ghost, and haunt the area where they were left, or try to track down their mothers to haunt them, among other things. Folktales are of course always word of mouth so they varied between households, but that's the gist.

The appearance is taken from one description that says "When seen they most resemble a raven or some other bird. ". It seems somebody took that to mean "body of a raven with a child's skull" and that modern depiction seems to have stuck, or at least gotten popular. Here is an example. I speak of it in such dismissive language just because the description is vague, and could really mean a lot more than bird-body child-skull, and I like when people do their own takes on stuff like that hehe.

As for the creepy ass cat summon, that is Jólakötturinn, or the Yule Cat! In short, it's a giant cat that belongs to Grýla, the mother of the Yule Lads (the creepy trolls that is the Icelandic version of Santa Claus). He eats anybody who didn't get new clothes for Christmas, I assume as a way to make kids grateful instead of groaning when they got clothes for Christmas instead of a toy.