The four sentences (labelled 1, 2, 3, and 4) given in this question, when properly sequenced, form a coherent paragraph. Decide on the proper order for the sentences and key in this sequence of four numbers as your answer.

1) The woodland’s canopy receives most of the sunlight that falls on the trees.
2) Swifts do not confine themselves to woodlands, but hunt wherever there are insects in the air.
3) With their streamlined bodies, swifts are agile flyers, ideally adapted to twisting and turning through the air as they chase flying insects - the creatures that form their staple diet.
4) Hundreds of thousands of insects fly in the sunshine up above the canopy, some falling prey to swifts and swallows

1 should be the opening sentence since it sets the context. Sentence 1 states that the woodland's canopy receives most of the sunshine that falls on the trees. Sentence 4 continues sentence 1 by stating that thousands of insects fly above the canopy in the sunlight. The insects fall prey to the swifts and swallows. 

We have to decide whether the order of the remaining 2 sentences is 32 or 23. 
Sentence 3 states that swifts are agile flyers, adapted to chasing flying insects. Sentence 3 states that flying insects form the staple diet of the swifts. Sentence 2 states that swifts do not confine themselves to woodlands and hunt wherever they can find insects. Therefore, sentence 3 should precede sentence 2 (We cannot introduce that insects form the staple diet after stating that swifts hunt wherever they can find flying insects).

Sentences 1432 form a coherent paragraph.
Therefore, 1432 is the correct answer.