dhabi writes in his book tazkira-tul-huffaz

وأما حديث الطير فله طرق كثيرة جدًّا قد أفردتها بمصنف ومجموعها هو يوجب أن يكون الحديث له أصل. وأما حديث: “من كنت مولاه…” فله طرق جيدة وقد أفردت ذلك أيضًا

as regards to hadeeth-e-tair, it has many chains which have been mentioned by the author in a book, and their collection makes it sure that the narration has a basis. and the narration: whosoever i am mola of, (ali asws is his mola), it has great chains which have been mentioned as well

[tazkira-tul-huffaz, dhabi, vol 3, page 1042-1043, 13th tabaqa, under heading:- hakim abu abdullah neshaburi, published by dar ul kutb ilmia, beirut, lebanon]

here is the online link