While the Eastern Whip-poor-will

[aditya8062]

While the Eastern Whip-poor-will --a nocturnal bird that feeds mostly in the very early morning-- and the Common Nighthawk --a nocturnal bird from the same family that, despite its name, feeds mostly during the morning and evening-- appear equal in size to each other when sitting on a branch or in a nest, in the air, the Common Nighthawk appears much larger due to its greater wingspan.

1 appear equal in size to each other when sitting on a branch or in a nest, in the air, the Common Nighthawk appears much larger due to its greater wingspan.
2 appear equal in size to one another when sitting on a branch or in a nest, in the air, the Common Nighthawk appears much larger due to its greater wingspan.
3 appear equal in size when sitting on a branch or in a nest; in the air, the Common Nighthawk appears much larger because of its greater wingspan.
4 appear equal in size to each other when they are sitting on a branch or in a nest, in the air, the Common Nighthawk appears much larger because of its greater wingspan
5 appear equal in size when they are seen on a branch or in a nest, in the air, the Common Nighthawk appears much larger because of its greater wingspan.

my concern: i am not able to accept the proclaimed answer (E) in this question .my concern is that the prepositional construction "in the air" in E can apply to the previous clause OR to the succeeding clause . so how do we know that to which clause it is applying?

[GMATGuruNY]

E: While the Eastern Whip-poor-will and the Common Nighthawk appear equal in size when they are seen on a branch or in a nest, in the air, the Common Nighthawk appears much larger because of its greater wingspan.

I agree that the placement of in the air is problematic.
Generally, if a sentence begins with while + SUBJECT, the first word after the while-clause should be the SUBJECT of the main clause.

Another issue:
One purpose of while is to indicate that two contrasting ideas are true AT THE SAME TIME.
E: WHILE the Eastern Whip-poor-will and the Common Nighthawk appear equal in size WHEN they are seen...
Since while on its own conveys a sense of time, when -- which also refers to time -- should not be used in conjunction with while.

One more issue:
APPEAR equal in size when they are SEEN
Since the birds must be SEEN in order to APPEAR equal in size, appear and seen are redundant.

I would ignore this SC.