On 21st April 2015, Melinda Chan sent in two images of a juvenile Black-shouldered Kite (Elanus caeruleus) photographed by Chan Yoke Meng (above, below). The kite was on a high perch spewing a sticky substance. There were two other juvenile kites on the same tree. They had a flock of Red-breasted Parakeets (Psittacula alexandri) as well as a single Hahn’s Macaw for company.
Was the kite regurgitating or vomiting?
According to the literature, regurgitation is part of the normal behavior of birds. When adults feed chicks or indulge in courtship feeding, food is forced out of the mouth, oesophagus or crop LINK. With the casting of a pellet, the compacted indigestible parts of the prey are forced out of the gizzard in the form of a pellet LINK. Regurgitation is also seen when a bird swallows a fruit and later ejects the seed LINK.
Vomiting on the other hand is the expulsion of the contents of the crop, proventriculus, ventriculus or intestine. Vomiting can be regurgitation in self defense against predators, as seen in Black-naped Terns (Sterna sumatrana) retaliating with vomit when an adult Grey Heron (Ardea cinerea) approached the colony LINK.
Southern Giant Petrel similarly “produces a stomach oil made up of wax esters and triglycerides that is stored in the procentriculus can be used as a projectile vomited on predators … The oil mats the feathers of birds together and destroys their waterproofing abilities, so soiled birds may die from chilling and/or drowning…” LINK.
Can this be a liquid projectile spewed by the Black-shouldered Kite? But then there were no attacker. Maybe it can be due to illness?
According to Dato’ Dr Amar-Singh HSS birds can vomit from illness but it is not possible to ascertain the cause here.
“Regurgitation in birds can be due to illness (known as vomiting), defence, casting pellets and feeding behavior,” wrote Amar, who provides a number of links below:
1. Vultures using defensive vomiting (acid) LINK.
2. Even gull chicks can spray oil in defence LINK.
4. Nice video HERE
According to aviculturist Lee Chiu San, “… parrots [and other birds] do throw up when they are sick, or when something that they have eaten does not agree with them.”
So the jury is still out in the case of this Black-shouldered Kite. It may well by illness but other causes may be possible. Anyone with an answer, please share with us.
Chan Yoke Meng, Melinda Chan, Dato’ Dr Amar-Singh HSS & Lee Chiu San