Amun is called Gengen Wer by which is meant the Nile goose and he is depicted in goose form all over Karnak. Hart in A Dictionary of Egyptian Gods and Goddesses says that it´s because Amun was associated with the act of creation, and Wilkinson in The Complete Gods and Goddesses of Ancient Egypt says that Gengen Wer is the primeval goose which manifested its power through his honking call or through carrying the egg from which life emerged. The Egyptian word gengen means 'honker' and wer means 'great'. So the Great Honker or Cackler. He also says that "according to some texts it was the honking call of Amun in the form of this god that 'awoke' creation." (p 213)

But Wilkinson also says that the goose was also closely associated with the earth god Geb who was sometimes himself called the great cackler, and was credited with having laid the first egg, when in goose form. So it´s Geb you are referring to, right? That was a really sly one! :) But Amun is more frequently associated with the goose and I´ve seen many a cartouche where the word 'Amun-Re' is written with the goose glyph and the sun glyph.

The goose was also, in later periods, associated both with Hapy and Harpocrates and Gengen Wer (according to Wilkinson)also appears in the Duat where the deceased can (not always) either be, or guard the goose egg.