There are a number of different characteristics that make it possible to identify birds, and one of the most prevalent is the bird's song. Birds use songs and calls to communicate with one another as well as to get around in low light and across long distances. There is a difference between bird songs and bird calls, and if you listen closely enough, you should be able to identify many species based on the sounds they make.
In comparison to bird calls, bird songs are more musical, and they tend to be more complex. Bird songs are almost exclusively produced by male birds, and they are learnt when the bird is young by listening to other males communicate. Bird songs play an important role in mating for many species of birds, as the female will choose a male based on his song. Many species sing in the morning and in the late afternoon, while other species may sing throughout the day. Some species have multiple bird songs for different purposes, such as mating and for protecting territory.
In comparison to bird songs, bird calls are not typically as musical. Most bird calls are comprised of a series of short notes, and they are used to communicate with one another. There are specific bird calls to meet different needs, such as to indicate warning, aggression, identification, hunger, flocking or to identify a food source.
One way to differentiate bird calls and songs is the number of notes, and then you can further categorise bird sounds based on the type of sound. Bird sounds and songs can consist of a single note, two notes or three or more notes. Bird sounds include clear whistles, harsh sounds, low-pitched sounds, notes repeating in a song, quacks and yelps. They may be repeated in a series, may have pitch changes or may be complex. By identifying characteristics of the bird song or sound, you can narrow down the potential species.
The first step in the identification of a bird sound is to identify the number of notes in the call. Sounds and songs that consist of a single note may include trills, honks, chips and hoots. Those consisting of two notes can vary in quality or pitch, while those that consist of three notes or more tend to be more complex. These more complex songs include squawks, whinnies and whistles.
You may need to categorise a bird song or call based on the pitch or the nature of the sound. Once you pare down potential species based on the number of notes, you can further fine tune based on what type of sound the bird makes. For example, clear whistles, harsh and unmusical sounds and low-pitched sounds are common single-note sounds. Multiple-note calls can be harsh and unmusical, low-pitched, short-duration calls, notes repeating as a song or clear whistles, depending on the species. Paring down your options further in this manner will make bird sound identification easier.