Chickadees lengthen the number of "dees" in their calls depending on the perceived threat of nearby predators based on size/speed: Templeton and his colleagues

Chickadees lengthen the number of "dees" in their calls depending on the perceived threat of nearby predators based on size/speed: Templeton and his colleagues tested the alarm call responses of a flock of six chickadees against the presence of 13 birds of prey predators, which ranged in size from the 40-centimetre wingspan pygmy owl to the 140-centimetre wingspan rough-tail hawk. They also tested responses against two mammals, a cat and a weasel. Each predator was inserted into the chickadees aviary and tethered to a perch. After analysing 5000 recorded alarm calls, the team found that the number of “dees” in the bird’s trademark “chickadee-dee-dee-dee” call corresponded to the size of the poised predator. Smaller hunters – which pose the greatest risk – received the most vociferous response. The alert causes the flock to mob their sitting foe in an attempt to drive it away. https://www.newscientist.com/article/dn7570-chirpy-chickadees-signal-deadliness-of-predators/ https://www.newscientist.com/article/dn7570-chirpy-chickadee...