Erik Christensen

Mykines is the westernmost of the Faroes and is notable for its puffins and gannets.  Wikipedia notes that the "Mykines house mouse" may have been introduced by Irish monks as early as the 6th century.

Navigatio Brendani 9.20: 

Posteā nāvigābitis ad aliam īnsulam, quae est nōn longē ab istā īnsulā contrā occidentālem plāgam, quae vocātur Paradīsus Āvium.

Navigatio Brendani 6.11: 

invēnērunt portum ubi erat aditus ūnīus nāvis.  

There are apparently a number of narrow fjords in the Faroes, but this one at  Gjógv, on the island of Eysturoy certainly seems like the kind of place our author had in mind.