A while back I mentioned my long-standing desire to post a list of things we don’t know about North American bird sounds, with an emphasis on the simple questions that amateur sound recordists could answer.  I’ve finally decided to take a crack at it.

Below, you’ll find my first attempt to list some things we don’t know.  It’s not even close to an exhaustive list, nor is it necessarily up-to-date — it’s merely a teaser, mostly based on a quick perusal of a few select BNA accounts.  My whole purpose is to inspire some amateur research projects. Most of these are questions that amateurs can answer in whole or in part.  You might be surprised at what you could contribute to science with a little time and energy.

Song Repertoire

How many different songs can one male bird sing?  This question can be easily answered by simply recording singing individuals for an extended period. The answer is sometimes quite different even between closely related species, or within populations of a single species.  Here are some birds whose song repertoires are poorly known.

• Northern Shrike
• Loggerhead Shrike
• Mountain Bluebird
• Virginia’s Warbler
• Black-and-white Warbler
• Hepatic Tanager
• Lark Sparrow
• Dickcissel
• Orchard Oriole

Begging Calls

An easy way to contribute is to record the sounds of young birds, either in the nest or out of it.  Ideally, locate a nest and monitor it, noting the dates of hatching and fledging, and making recordings on a regular basis in between, to document the development of the sounds.

• Mountain Bluebird
• Lucy’s Warbler
• Dickcissel
• Blue Grosbeak
• Spotted Towhee

Geographic Variation

Birds in this category may sound different in different parts of their range.  Some of these differences may have taxonomic implications.  On the other hand, some of these birds may not sound much different across their ranges; we don’t really know.

• Cave Swallow
• Curve-billed Thrasher
• Spotted Towhee (calls)
• Great-tailed Grackle

Call Repertoire

The birds in this category may make sounds that do not appear on commercially available bird sound recordings and are poorly described in the scientific literature.  To solve the problem, we need recordings of all the sounds birds make — not just the pretty ones, or the loud ones — plus detailed notes on the behavioral context of the sounds: what was the bird doing when it made the sound?  What time of year and day was it?  What was the bird’s age and sex?  And so forth.

• Clark’s Grebe
• Common Moorhen
• Olive-sided Flycatcher
• Greater Pewee
• Loggerhead Shrike
• Blue Grosbeak
• Vesper Sparrow
• American Tree Sparrow (more on this in an upcoming post)
• Pine Siskin
• Bullock’s Oriole

Spectrographic Analysis

Many vocalizations have been described in the literature only phonetically, and it can be difficult to determine which call the author was hearing — or which one you are hearing — unless you have spectrograms to compare.  These species could use a formal description of repertoire with spectrograms:

• Northern Shrike
• Phainopepla
• Common Myna
• Bewick’s Wren (calls)
• Rock Wren
• Hepatic Tanager
• Summer Tanager
• Lark Sparrow

Flight Calls

Not enough flight calls have been recorded from these species (during the daytime) to determine the limits of variation in the sounds they might make during nocturnal migration.

• MacGillivray’s Warbler
• Western Tanager
• Black-headed Grosbeak
• Brewer’s Sparrow
• Western Meadowlark

Other Questions

• Goldfinches (at least Lawrence’s and Lesser, and probably American also) apparently sing two types of songs: a long, continuous one and a disjointed one that sounds like a long string of calls.  The two song types grade into one another.  The disjointed song has never been described in the literature and its purpose and behavioral context remain unknown.
• Male Painted Buntings may continue learning new songs after their first year of breeding; extensive recordings of the same individual across multiple years would help resolve the question.
• The BNA account on Bullock’s Oriole says that “Males seem to sing only a single song,” but I suspect the situation is much more complex, as it is in the closely related Baltimore Oriole.  Shall we find out?

And that, folks, is just what I found in a perusal of roughly 50 BNA accounts.  This is just scratching the surface.  Note how many common and widespread species are on the above lists.  Everybody in North America can contribute if they’ve got the time — and especially if they have recording equipment.

If you’ve got anything to add to this list, post it in a comment!  I’ll try to get a master list put together eventually.