Identifying Veery/Scarlet Tanager and Song/Fox Sparrow Nocturnal Flight Calls

These two pairs of calls have caused a great deal of headaches in the NFC community and have even been considered inseparable. In this post I'm going to try to see if we can identify them.

Scarlet Tanager/Veery Calls:
Scarlet Tanagers have a clear bisyllabic call termed "puwi" by Evans and O'Brien which is distinctive and most likely the main nocturnal flight call, although it is heard comparatively infrequently at night. It's not this call but the burry "hu-dee", which sounds similar to the most common Veery NFC, that is the source of confusion. It features on the Evans O'Brien CD-ROM as a rare variant, and the example given was a diurnal recording. "Hu-dee" is found as a component of the Scarlet Tanager song (which is not uncommonly given during nocturnal flight), and is the begging call of fledglings and of the adult female during the courtship/nesting period. The use of a begging call during nocturnal migration is unusual; the only other Eastern US species that I'm aware of that has a begging call similar to a nocturnal flight call is Rose-breasted Grosbeak.
The following examples of the "hu-dee" call have a spectrogram that is either M, W or N-shaped, with a larger frequency range than Veery. Compare that to the shallow U-shaped Veery spectrograms.



Presumed migrant (perched, 7.00am, late Sep, PA).

Begging juvenile from YouTube video (https://www.youtube.com/watch?v=CkPCyWc3x_M).

Xeno-canto recording of presumed begging juvenile (Aug, MI).

Begging juvenile (early Sep, PA).

Adult female on nest, begging call, being fed by male (May, PA).

From "Flight Calls of Migratory Birds" WR Evans and M O'Brien.

From "Flight Calls of Migratory Birds" WR Evans and M O'Brien.

Perched Veery (May, PA).

Perched Veery (Sep, PA).

Perched Veery (first few calls, June, PA).

Veeries have a wide range of nocturnal (and diurnal) calls and there may be some that cannot be safely separated from the "hu-dee" of the tanagers (Summer Tanagers have similar calls), if in fact this call is used as a nocturnal flight call. Most calls should be separable by pitch range and structure.



Fox/Song Sparrow calls:
In the field I can often identify Fox Sparrows by their clear rising bisyllabic call which to me is usually distinct from that of Song Sparrows. I actually have more trouble separating Song Sparrows from White-throated Sparrows. It appears though that identifying Fox from Song Sparrow is a problem among NFCers because of the similarity of the spectrograms. I went through my recordings of seen birds to see if there are any differences in the spectrograms to explain the differences I notice in the field.

Fox Sparrows:
(Jan, NJ).

(Nov, PA).

(Nov, PA).

(Mar,NJ).

(Mar, PA).

(Dec, NJ).

Note the increased gap at the nadir in this sample.






Song Sparrows:
(Oct, NJ).

(Nov, PA).

(Dec, PA).

(Aug, PA).

(Nov, PA).

(Nov, PA).

An anomalous rising call (Mar, PA).

Fox Sparrow calls almost always have a larger rising component, and look like a fallen over letter J. Song Sparrow calls usually are a rather symmetric U-shape. The larger gap between the bands at the low point of the Fox Sparrow call may be significant. Of course there are unidentifiable calls but most calls adhere to this description. Does this translate into differences between nocturnal flight calls? I would say that NFC's are likely to be more variable but many should be identifiable.