Nos livros os Eagles são :
sentient and capable of speech
Nos filmes (O Hobbit, Senhor dos Anéis) nós nunca os ouvimos falar.
No livro O Hobbit Gandalf não ligue para o Eagles para ajudar, mas:
Luckily for the company, the Lord of the Eagles has seen the commotion from his roost high in the mountains. With a number of other eagles, he swoops down, picks up the marooned travelers, and flies them to safety.
The eagles are friends of Gandalf’s and enemies of the goblins. They are happy to provide food and rest for the weary travelers, who then continue on their journey.
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Although the eagles help the company tremendously, they express that hatred for goblins, rather than love for dwarves, is their main reason for helping the company.
... the eagles [don't] have any interest in the dwarves’ gold, but as representatives of pure nature, they are the sworn enemies of corrupted nature, represented by the goblins and Wargs.
The eagles generally keep distant from the affairs of other races...
Houve uma pergunta semelhante em relação ao Senhor dos Anéis :
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Por que as águias não voam com o Anel para o Monte da Perdição?
It seems that nobody noticed this alleged plot-hole during Tolkien's lifetime, as there is no surviving letter where Tolkien is inquired so. It is unknown whether Tolkien ever was aware of the issue while writing the book or later.
Tolkien's only relevant mention is concerning a possible adaptation of the Lord of the Rings into a movie, where he simply mentions that the Eagles should be used carefully as a plot device and was self-aware whenever he used them.
Existem algumas teorias sobre por que os Eagles não foram usados.