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Learning flight calls
Learning to identify flight calls is like learning to hear a new language - a process that demands dedication, concentration, and repetition. But once the language is learned, it expands the range of your birding significantly. Not only can one detect and identify more birds during the day, but one can tune into their nocturnal migration and surmise what is passing over unseen at night (see below). Although good hearing ability is the essential foundation for learning (and, indeed, hearing) flight calls, it is equally important to have a well-trained ear. Learning how to listen analytically is perhaps the biggest hurdle to overcome. Most flight calls are very short and that makes it difficult for the human ear to process the sound in a meaningful way. In fact, most people assume that they do not have the ability to discriminate such calls. But, by directing your attention to the matter, it is possible to train your ears to detect subtle differences in sounds that would normally go unnoticed.
While listening to an unknown call, it is helpful to consider a variety of parameters. For example, how long is the call? Does it have an obvious pattern or is it simple? How high is the pitch? Is it rising, falling, arched, or evenly-pitched? Is the call modulated (buzzy) or pure-toned (smooth)? How loud is the call? Is the call loudest in the beginning, middle, or end, or is it even throughout? It is always helpful to compare an unknown call to a familiar bird call or other familiar sound. With a direct comparison in mind, it is easier to describe the call to yourself and, thus, remember it.
The most fundamental step in learning a flight call is to first identify the bird visually. Following a bird around and listening to all the calls it makes is a good start. With many species, the flight call will be uttered by foraging birds on the ground or in short flights. On the breeding grounds, the many vocalizations uttered between adult birds and their young will often include flight calls. During migration, a good strategy is to go to a concentrated migration point such as a coastline and study birds in morning flight (see "morning flight" in glossary). This provides a unique opportunity to see and hear many primarily nocturnal migrant species still in their active migration mode when they give their flight calls most frequently. Needless to say, it takes much practice to identify some of these birds in flight and many will remain unidentified. However, the challenge of identifying flying songbirds is worth the effort for those interested in learning flight calls.
Learning nocturnal flight calls
One of the most rewarding aspects of learning flight calls is the increased awareness one gets of the migrants that are passing over in nocturnal migration. Species that are skulkers during the day can migrate through an area largely undetected until their nocturnal flight calls are learned. For example, on a good night, it may be possible to hear hundreds of thrushes pass over a single listening location where, during the day, one would be lucky to find just a few. Similarly, species that are uncommon in a region (such as Dickcissel on the east coast) are sometimes more easily detected by their nocturnal flight calls. Even if only a small portion of the calls can be identified to species, the experience of listening to a night flight can be enchanting and enlightening.
In attempting to learn nocturnal flight calls, one begins by sorting calls into different groups. Broadly speaking, most calls heard at night fall into two categories: thrush-like whistles and high "seep" or "zeep" calls from warblers and sparrows. Warblers generally have the shortest and highest-pitched flight calls. They are mostly between 1/10th and 1/20th of a second or less in duration and above 6 kHz in frequency. They sound somewhat like a single cricket chirp. Among the warbler flight calls, many fall into two categories: those that are buzzy (such as the "dziit" of a Yellow Warbler) and those that are more pure-toned (such as the "seemp" of a Palm Warbler). Sparrow calls are similar to warbler calls, but they tend to be slightly longer, such as the drawn-out "tseedt" of a White-throated Sparrow. Thrush calls are typically longer and lower-pitched than warbler or sparrow calls, usually 1/5th to 1/10th of a second in duration and between 2 and 4 kHz in frequency (e.g., the "pwee" of Swainson's Thrush). Breaking down flight calls into broad groups such as these is often a good first step to identifying them. Although not all flight calls will fit neatly into one group or another, just attempting to classify them like this will force the listener to hear the call in more detail and begin the process of their identification.
Listening to nocturnal migrants can be done in any quiet location but hilltops tend to be better than valleys. Coastal areas are sometimes particularly good for listening as migrants tend to concentrate there under certain weather conditions. In towns and cities, locations with bright artificial light may disorient bird navigation, and this leads many species to vocalize more. Cloudy nights are usually better for listening than clear nights, as this seems to force migrants down a little lower and may even entice them to call more frequently.