"The bird is eating the flies."
Translation:Der Vogel frisst die Fliegen.
The hint ordering got confused because the word "the" shows up twice in the sentence.
I believe that in such a case, it always sorts the hints the same way.
For the first "the" (in "the bird"), der is an appropriate hint.
For the second one (in "the flies"), it's not.
But the hint ordering isn't clever enough to know which "the" corresponds to der and which one corresponds to die and it shows the same ordering for both.
Which is one big reason why you can't rely on the hints for "recommendations" or "suggestions".
The words are Vogel, Bär, Katze with a capital letter at the beginning -- all German nouns are capitalised; the capitalisation is part of their spelling. There is no German word vogel or bär or katze.
We say der Vogel because the word Vogel is masculine.
We say die Katze because the word Katze is feminine.
We say das Pferd because the word Pferd is neuter.
The grammatical gender of a noun in German is mostly arbitrary. Just look it up and remember it.
(Also, der Katze would be appropriate in the genitive or dative cases, as der is the article not only for masculine nominative but also for feminine genitive, feminine dative, and plural genitive.)
Why is it "Der" before "Bird?"
It isn't. "Der Bird" makes no sense in either language.
What we have here is "the bird" in the English sentence and der Vogel in the German sentence.
The word Vogel is grammatically masculine, so "the bird" is der Vogel, with the masculine article der.
Note that the grammatical gender is associated with the German word -- not with an English word or with a general concept.
It's just one bird, would it not be "Die?"
No. die is for feminine words and for plural words.
In the plural, you would have die Vögel (with umlaut in this case).