How to listen for the song of the Kirtland’s Warbler

 

Many bird species have vocalizations that can be difficult to pin down and, yes, the Kirtland’s Warbler is one of them. Depending on the conditions and the position of the bird, the song of a Kirtland’s Warbler might on one day sound loud and clear then change to be distant and muffled—even if it’s calling from the same location. 

 

Understanding how to hear a Kirtland’s song is critically important to the success of the census because you will be hearing multiple birds at multiple locations as you are walking your transect and stopping at designated listening points. 

 

So, here are some suggestions on how to listen to the bird’s vocalizations to determine its position relative to your census route.

 

The first step is to determine how close a vocalizing bird is to you. Generally, the closer a singing Kirtland’s Warbler is to you, the louder it will be. But keep in mind that several things can impact how you perceive a bird’s volume.

• There can be a big difference in the detectable volume if the bird is singing out in the open, high on a snag or low in the pines. 

• There can also a big difference in detectable volume if the bird is facing away or toward you, even if singing from the same perch.

• Weather and site conditions will affect the volume.  For example, volume will be lower if the wind is blowing the sound away from you and potentially louder if the wind is blowing in your direction. Also, noises from other birds, insects, and human sources may reduce the relative volume of the Kirtland’s warbler song.

 

Bottom line: Listening carefully for subtle changes in volume can help you track the bird’s position. 

 

Okay, you probably have figured out how far the bird is from you, but what about its location?  You probably don’t realize it as you are listening to a bird vocalize, but your brain is already working to register its location because the sound waves made by the vocalization reach your ears at different times—a difference that can be registered in milliseconds. That oh so subtle difference is often enough to let your brain say, “It’s in that direction.” 

 

We can use this knowledge to further hone in on the location of a vocalizing bird by doing a couple of different things:

 

1. Cup your ear. Yes, it’s obvious and it’s a bit silly but it’s always good to remember that holding your hand up to your ear and tilting the outer ear toward the sound you want to hear can increase sound reception by as much as 10 decibels. 

2. Rotate your head while listening to the bird sing can help you improve the direction the vocalization is coming from based on which ear is picking up the sound best.

3. Try turning your head sideways, with one ear aimed at the ground and the other toward the sky. This small reorientation of your ears will help you locate how high or low the bird might be in a tree.

4. Because the forest absorbs sound waves, it’s unlikely you will hear an echo of the bird’s vocalizations. However, you should be conscious that it is possible to hear the same bird from different directions, depending on the conditions or if it moves to a different location. 

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Bottom line: Don’t be afraid to try old gimmicks to locate a bird. They actually work!

 

Finally, listening for subtle differences in vocalizations can help you track singing males. The Kirtland’s Warbler may use several alternate songs and calls. The loud, “bubbly," relatively long and more commonly heard song contrasts with an alternative song that is usually quieter and sounds like its regular call crossed with a chatter. Be aware that there are outlier birds with very different songs. One researcher, Sarah Rockwell, could identify a specific Kirtland’s Warbler because its song reminded her of a horse’s whinny. She also noted that a Kirtland’s Warbler slurs its song when it attempts to sing with food in its mouth. 

 

Besides listening for the direction of the calls at each stop along the transect, you should also listen for the frequency of calls and the length of time between calls.  This is important because you may have two birds in close proximity.  It would easy to count those two birds as one, but at some point, it’s likely that the two calls will occur either simultaneously or too close together in time to come from a single bird.

 

Bottom line: Identifying subtle differences in songs can help you distinguish between different birds and improve the count’s accuracy. 

 

To review the most common song of the Kirtland’s Warbler, click HERE. (Recording by Ron Overholtz.)

Compare that to the alternative (“chatter”) song of the Kirtland’s Warbler by clicking HERE. Recording by Andrew Spencer.)

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One more thing: Working in advance to improve your listening skills will help you in the field but it will also allow you to impress your weekend birding buddies when you are able to locate birds by their vocalizations before they do!