Chekhov and the omission of "be" verbs with progressive tenses in compound sentences

The following is an excerpt from a translation of Chekhov's story "The Student" published in the Norton Critical Editions. Given the prestige of this publication, one would assume what's printed to be, at the very least, grammatically correct.

Is the following sentence correct? If so, how might we parse it to warrant this judgement?

The blackbirds were calling and a creature in the nearby swamps plaintively hooting as if blowing into an empty bottle.

• Anton Chekhov's Selected Stories Texts of the Stories, Comparison of Translations, Life and Letters, Criticism. New York: W.W. Norton & Company, 2014.

I don't why the author doesn't need to use the 'be' verb with the progressive tense in the second clause, like so:

"The blackbirds were calling and a creature in the nearby swamps was plaintively hooting as if blowing into an empty bottle."

Solution 1:

First, the sentence is grammatical. But, yes, as you point out, the 'to be' is necessary for the second clause in order to be grammatical. This sounds contradictory but it is not.

The 'were' needed for the second clause actually is there. It's the 'were' before 'calling'. It is doing double duty.

This is an instance of parallelism, where a repeated identical (or very similar) part is dropped so as not to appear repetitious. It's grammatical and actually gives a more formal feel to things. You don't have to drop it - it's just a stylistic choice.