It’s the time of year when sparrows sing, and none more enthusiastically than the Song Sparrow. These males could be seen and heard on the north side of the park almost every morning not long after sunrise.
Wikipedia has this to say about their song:
The sparrow species derives its name from its colorful repertoire of songs. Enthusiasts report that one of the songs heard often in suburban locations closely resembles the opening four notes of Ludwig van Beethoven‘s Symphony No. 5. The male uses a fairly complex song to declare ownership of its territory and attract females.
Singing itself consists of a combination of repeated notes, quickly passing isolated notes, and trills. The songs are very crisp, clear, and precise, making them easily distinguishable by human ears. A particular song is determined not only by pitch and rhythm but also by the timbre of the trills. Although one bird will know many songs—as many as 20 different tunes with as many as 1000 improvised variations on the basic theme,—unlike thrushes, the song sparrow usually repeats the same song many times before switching to a different song.
Song sparrows typically learn their songs from a handful of other birds that have neighboring territories. They are most likely to learn songs that are shared between these neighbors. Ultimately, they will choose a territory close to or replacing the birds that they have learned from. This allows the song sparrows to address their neighbors with songs shared with those neighbors. It has been demonstrated that song sparrows are able to distinguish neighbors from strangers on the basis of song, and also that females are able to distinguish (and prefer) their mate’s songs from those of other neighboring birds, and they prefer songs of neighboring birds to those of strangers