From Francis Willoughby and John Ray (1678) The Ornithology of Francis Willoughby, in Three Books etc., Book III, Part III, Sect. VII, Memb. I, Chap. I, §II (!!) (pp. 357-358):
The Wind-pipe reflected in form of a Trumpet seems to be so contrived and formed by nature for modulating the voice. Hence what the Ancients have delivered concerning the singing of Swans (if it be true, which I much doubt) seems chiefly to agree to this bird, and not to the tame Swan.
For my part, those stories of the Ancients concerning the singing of Swans, viz. that those Birds at other times, but especially when their death approaches, do with a most sweet and melodious modulation of their voice, sing their own Nænia or funeral song, seemed to me always very unlikely and fabulous, and to have been therefore not undeservedly exploded by Scaliger and others. Howbeit Aldrovandus, weighing on both sides the Arguments and Authorities of learned men, hath (he saith) observed them to be equal; wherefore to cast the scale, and establish the affirmative, he thinks that wonderful structure of the Wind-pipe, by him first observed, is of weight sufficient. But this Argument though it be very specious and plausible, yet doth it not conclude the controversie. For we have observed in the wind-pipe of the Crane the like ingress into the cavity of the Breast-bone, and reflection therein, or a more remarkable one; yet no man, that I know of, ever commended the Crane for singing, or musical modulation of its voice. But if you ask me, to what purpose then doth the Wind-pipe enter into the breast-bone, and is in that manner reflected there? I must ingenuously confess, I do not certainly and fully know. Yet may there be other reasons assigned thereof; as that which Aldrovand alledges in the first place,1 1. That whereas sometimes for almost half an hours space the Swan continues with her heels up, and her head under water, seeking and gathering up her food from the bottom of the Pool or River she swims in, that part of the Wind-pipe enclosed in the breast-bone may supply her with air enough to serve her all that while. So the use of it will be to be a store-house of air, for the advantage of diving and continuing long under water. 2. This kind of structure doth undoubtedly conduce much to the increasing the strength and force of the voice. For that the wild Swan hath a very loud and shrill cry, and which may be heard a long way off, the English name Hooper, imposed upon it (as I suppose) from its hooping and hollowing noise doth import.
Hence it appears how uncertain and fallacious a way of arguing it is from the final cause. For though Nature, Gods ordinary Minister, always acts for some end, yet what that is we are often ignorant, and it doth not rarely fall out to be far different from what we fancy : Nay we may be deceived when we think we are most sure, and imagine it can be no other than what we have presumed.
Wherefore I make more account of the testimonies he alledges; as of Frederick Pendasius, that affirmed he had often heard Swans singing sweetly in the Lake of Mantua, as he was rowed up and down in a Boat. But as for the testimony of George Braun concerning flocks of Swans in the Sea near London, meeting, and as it were welcoming the Fleets of Ships returning home with loud and chearful singing, it is without doubt most false: We having never heard of any such thing.
Olaus Wormius2 of late confirms the opinion of Aldrovand, and the reports of the Ancients concerning the singing of Swans, producing Testimonies of some of his familiars and Scholars who professed themselves to have heard their music. There was (saith he) in my Family a very honest young man, one Mr. John Rostorph Student in Divinity, a Norwegian by Nation. This man did upon his credit, and with the interposition of an Oath solemnly affirm, that himself in the Territory of Dronten did once by the Sea-shore early in the Morning hear an unusual and most sweet murmure composed of most pleasant whistlings and sounds: Which, when as he knew not whence it came, or how it was made, for that he saw no man near which might be the author of it, looking round about him, and climbing up the top of a certain Promontory, he espied an infinite number of Swans gathered together in a Bay of the Sea near hand, making that harmony; a sweeter than which in all his lives time he had never heard. By some Islanders, my Scholars, I have been told, that nothing is more frequent with them that this harmony, in those places where there are Swans. This I therefore alledge, that it may appear that the report of those famous ancient Authors concerning the singing of Swans is not altogether vain, but attested and proved by modern experiments. Thus far Wormius. Let the Readers judge whether his witnesses be sufficient.
This Bird hath not as yet, that I know of, been described by any Author.
1. Ornithol. c. 3. p. 19.
2. Musæ. book 3. chap. 13.