This sentence is not correctly punctuated.
The correct version would be:
"Soon after they hatch, plover chicks can walk on their own. However, they cannot fly for at least a month, making it difficult for them to evade the human onslaught on sunny summer days".
The conector "however" appears almost aways at the beginning of the sentence. In some rare cases it may appear between commas, but only when followed by a verb; or a the end of the sentence. Therefore, we need to separe this sentence in two and place a comma after "however".
The comma before the phrase "for at least a month" is incorrect because the phrase is modifying the verb "fly", so they cannot be separated. By putting a comma before and one after it, we transform the phrase into a parenthetical phrase that makes no sense withing the sentence.