Perhaps the most challenging group of songbirds to identify by sound are the trillers. The species we will be examining in this post are Pine Warbler, Orange-crowned Warbler, Worm-eating Warbler, Palm Warbler, Chipping Sparrow, Swamp Sparrow and Dark-eyed Junco. Don’t worry if you can’t seem to get this songs because I still struggle with many of them as well. The individual notes are sung so quickly that our brains cannot help but hear the song as a continuous trill but birds can process songs more slowly so they can tell the difference. And it is there – as the sonograms show – in each individual note. Whether a note is upslurred, downslurred, overslurred or underslurred gives each trill a subtly different quality but the difficulty is in training your ear to recognize this difference. If you need a refresher on some of the terms used in this post, refer to my post on an introduction to sonograms and birdsong vocabulary: https://apassionforbirds.wordpress.com/2014/06/24/introduction-to-sonograms/.
Let’s start with what is often the easiest to eliminate from this group. The Orange-crowned Warbler gives a song that is often thinner, faster and more staccato than a Chipping Sparrow’s song. However, they key element in this song is the fall in pitch that usually comes at the end (as seen in the sonogram). Regardless, individuals can give a constant-pitched song so it can help to know the difference in overall tone. In other words, if the pitch falls, it is almost certainly an Orange-crowned Warbler but if the pitch remains level, you have not ruled out Orange-crowned Warbler yet. Even if the pitch does not fall, this song usually has a quality of varying somewhat in pitch compared to the Chipping Sparrow and is typically shorter than the Chipping Sparrow’s song. Each note is an underslur as shown in the sonogram.
Now onto another song that, with practice, can come pretty easily. The Pine Warbler’s song sounds the most gentle and musical out of all of the trillers other than the Samp Sparrow. It usually is slower than the Chipping Sparrow and increases in volume. However, it can give a faster song as well. In the recording from xeno-canto.org, the individual gives two different variations of its song – the first more musical as seen by the more complex and less steep notes in the first sonogram. Compared to the Swamp Sparrow, the Pine Warbler gives a less staccato song where the notes blend together more.
Yet another species that stands out in this group is the Worm-eating Warbler. This bird’s trill is so quick that you are more likely to confuse it with an insect than another bird. The only bird of this group with which you could possibly confuse it would be the Chipping Sparrow. However, the Worm-eating Warbler’s song is usually faster, thinner, more metallic, increases more in volume and is shorter overall than the Chipping Sparrow’s song. you can tell by the steepness of each note how metallic and lacking in musicality this song is.
The Chipping Sparrow’s song is typically longer and more steadily pitched than the songs of the other trillers. The song is usually mechanical and dry but not as much as the Worm-eating Warbler’s song. It is even0paced and, as shown by the closeness of the notes, often has a buzzy sound to it.
Buzzy Series: http://macaulaylibrary.org/audio/105834
The Palm Warbler’s song can vary quite a bit in the speed and tone. Typically, the song is distinctively slow – to the point it becomes more of a series of buzzy notes rather than a trill. Occasionally, the tone gets sweeter and the song becomes more of a trill. A third variation produces a more mechanical trill that sounds similar to a Chipping Sparrow’s trill but is usually shorter.
The Dark-eyed Junco has a slow, sweet, short and musical trill. Notice that each of the note pairs are downslurred. This species usually repeats its trill more often than the Chipping Sparrow. The musical trill is more ringing and thinner than the Pine Warbler.
The Swamp Sparrow gives a loose, slow, musical trill that is typically shorter and stronger than the Chipping Sparrow. Each note pair is downslurred. The trill often also falls off in volume at the end. This trill can sound quite similar to that of the Dark-eyed Junco but luckily, the habitat of these two species are quite different. Swamp Sparrows are found in freshwater marsh and in vegetation at the edges of ponds whereas Dark-eyed Juncos are found in open mixed forests.