NFCs: Cape May Warbler

The flight call of the Cape May Warbler is given year-round, including during nocturnal migration, and is distinctive (with several look-alikes). Several characteristics can be used to distinguish CMWA from other descending calls including Pine Warbler, Prairie Warbler, and Northern Parula.

Example Spectrograms

CMWA Spectrogram

Published References

Pieplow (2017) refers to the flight call as “tsew” that is

barely buzzy, slightly downsurred

Dunne (2006) describes the flight call as

a very high breathy “zwee” which, at close range, also has a light vibrancy

Stephenson, et al (2015) describe the flight call as

“falling, short, very high”

and

"Very short, high, often falling a bit in pitch"

Sibley (2016) says the flight call is

a very high, slightly buzzy tzew slightly descending

Evans and O'Brien (2002) writes:

A piercing, usually downward-arched and/or slightly descending "tszp" or "tzew".

And describes it like this:

Measured calls (N=17) were 37.5-55.3 (46.2) mS in duration and in the 6.4-8.8 (6.9-8.3) kHz frequency range. The frequency track was usually single-banded but occasionally showed a faint second band. It was typically descending and often slightly downward-arched and was modulated with 3.5-6 (5) humps with a spacing of 7.3-9.8 (8.6) mS and a depth of 0.4-0.7 (0.5) kHz.

Dunn and Garrett (1997) note:

Flight note a soft buzzy zeet, slightly softer than similar flight notes of Yellow, Blackpoll, Bay-breasted.

Example Calls

Here is an example of multiple calls given by a bird, seen and heard, during a Cape May, NJ migration watch: https://macaulaylibrary.org/asset/120493231

Other calls:

Salient Points

This section may not be helpful. The idea is to make it easier to rule out other species more easily without going through the whole list, which may not be possible.

There are three characteristics that, together, can readily distinguish Cape May Warbler from any similar species. Namely:

  • Distinctive “descending arc” shape – Frequency higher at the start than the finish, with the highest point being somewhere in between.
  • High Frequency – Approaching 9 kHz, this call is at the high-end for most warbler flight calls.
  • Strong modulation – Other calls with general shape and frequency that are closest to Cape May lack the strong modularity of Cape May.

Similar species

The following species were noted as being similar by the cited experts. Any notes underneath the species can be used to rule out the other species for particular calls.

When describing this call in comments on an NFC checklist, try and add as many salient notes as possible and refer to this page for justification. If there are any species which seem similar, please get in touch so we can add them here. The intent here is to have a full list of differences for each possible similar call.

All notes for species are coming from Evans and O'Brien (2002), unless where noted.

  • Northern Parula
    • lower, less buzzy, and more steeply descending than CMWA
    • Often has slight, downward hook at the beginning
  • Pine Warbler
    • lower, softer, and more pure-toned than CMWA
    • More finely modulated than CMWA
  • Prairie Warbler
    • Softer, lower, and not as buzzy as CMWA
    • Typically double-banded and unmodulated.

References

  • Dunn, J. L., & Garrett, K. (1997). A field guide to warblers of North America (Vol. 49). Houghton Mifflin Harcourt.
  • Dunne, Pete (2006) Pete Dunne's Essential Field Guide Companion. Houghton Mifflin Harcourt: New York.
  • Evans, W. R. and O’Brien, M. (2002) Flight Calls of Migratory Birds Eastern North American Landbirds. Old Bird Inc. [CD-ROM]. Online
  • Pieplow, Nathan (2017) Peterson Field Guide to Bird Sounds of Eastern North America. Houghton Mifflin Harcourt: New York.
  • Sibley, David (2016) Sibley Birds East. Knopf: New York.
  • Stephenson, Tom and Whittle, Scott (2015) The Warbler Guide. Princeton University Press: Princeton, New Jersey.