- Birds make many different sounds each with a very unique function
- Songs for mate attraction: one of the principal ways a male signals his fitness to females during the breeding season. Usually sung in the late morning and throughout the day.
- Songs for territory defense: used to signal to territory neighbors or interloping males that his territory is taken. Usually sung first thing in the morning to let neighbors know the territory holder is still around. Males learn the songs of their neighbors, but when they don’t recognize a song the location it is being sung from they will investigate and chase of an intruder if he has passed the territory boundary.
- Flight calls: used only during migration to communicate to individuals migrating together in a flock, this keeps individuals within a flock from drifting apart. This call notes are unique to each species, but flocks can be made up of multiple species.
- Other calls: birds make many other call notes, especially throughout the breeding season. There are unique calls used for communication between the adults when feeding nestlings, used to alert each other when one parent has arrived at the nest with food.
- Calls used for communication between the parents and the nestlings and recently fledged birds. A different set of calls used when there is a predator around the nest area, this is often used to try and persuade the predator to follow them rather than look for the nest of eggs or defenseless nestlings. This is often coupled with a distraction display where a bird will feign an injury in the hope that the predator will perceive the parent as easy prey and be lead away from the nest area. A great example of this is Killdeer using a broken wing display.
- Plumage: in almost all sexually dimorphic bird species the males have brighter plumage than females. This is especially true for most male warblers; females use plumage condition and brightness to judge male quality characteristics. Usually brighter individuals are excellent at finding food, when certain food is consumed during the active molt period in the fall and the spring certain pigments such as carotenoids are metabolized in the feather production with then affects the color of the molting feather. Females see brighter males as a sign of a highly proficient forager and thus would be good at providing food for her and the nestlings they will raise together.
- Exaggerated plumage adornments also signal male quality characteristics. The best example of this is with the birds of paradise, where it takes many years to attain the elaborate plumage that the females are selecting. Thus this is a way to weed out only the best males, many of which are older and more experienced than younger less showy males.
- Dancing: Andean Cock-of-the-Rock. Leks where many males gather to dance and show off their dancing skills to try and attract watching females. Manikins have elaborate dancing routines involving one older male and several subordinate males to impress a female.
- Dancing in the sky: American Woodcocks have flight flight displays between bouts of calling. On the decent the male uses the modified outer primary feathers to create a series of zip, zap, zip sounds. The flight display and calling are used to show they are healthy individuals and the females should mate with them.