The Trumpet Manucode (Phonygammus keraudrenii) has an exceedingly long and coiled trachea, that enhances the resonance of its call. Yes, all those coils visible in the torso are the trachea, which is many times longer than it needs to be to connect the head to the lungs. Birds-of-paradise do this sort of thing a lot.
Why would evolutionary pressures ever come up with such things?
https://zoologyweblog.blogspot.com/2014/10/curl-crested-manucode-seen-and-heard.html
A long trachea means more dead space. The tidal volume—the volume of gas inspired or expired per inhalation—must be greater than in a bird with a short trachea. No matter how efficient the avian lung is at exchanging oxygen and carbon dioxide—and it is really efficient—the volume of air inhaled first into the posterior air sacs before passing through the lungs must be greater. Only birds, with their extensive system of air sacs, can afford such a long trachea (giraffes would be the nearest mammalian equivalent—to see how they do it) since only they can generate such a large tidal volume. But a long trachea must bear a metabolic cost since the fuel to power the muscles that generate the large tidal volume must be supplied continuously. In this respect it is interesting to note that Clench concluded that the increasing complexity of the tracheal loops occurs as the males age (in females the trachea stays relatively simple). So does a more successful male produce a sound more enticing to the female and thus signal the fact that it can afford to invest in a longer trachea, and/or to other males that if you come near me, I am older, fitter and can see you off? In either case the signal would be an ‘honest’ signal of the quality of the male.
Curl-crested Manucode: Unusual Anatomy
https://www.youtube.com/watch?v=0C6EbpDks-A
Why would evolutionary pressures ever come up with such things?
https://zoologyweblog.blogspot.com/2014/10/curl-crested-manucode-seen-and-heard.html
A long trachea means more dead space. The tidal volume—the volume of gas inspired or expired per inhalation—must be greater than in a bird with a short trachea. No matter how efficient the avian lung is at exchanging oxygen and carbon dioxide—and it is really efficient—the volume of air inhaled first into the posterior air sacs before passing through the lungs must be greater. Only birds, with their extensive system of air sacs, can afford such a long trachea (giraffes would be the nearest mammalian equivalent—to see how they do it) since only they can generate such a large tidal volume. But a long trachea must bear a metabolic cost since the fuel to power the muscles that generate the large tidal volume must be supplied continuously. In this respect it is interesting to note that Clench concluded that the increasing complexity of the tracheal loops occurs as the males age (in females the trachea stays relatively simple). So does a more successful male produce a sound more enticing to the female and thus signal the fact that it can afford to invest in a longer trachea, and/or to other males that if you come near me, I am older, fitter and can see you off? In either case the signal would be an ‘honest’ signal of the quality of the male.
Curl-crested Manucode: Unusual Anatomy
https://www.youtube.com/watch?v=0C6EbpDks-A
