Pine Warbler (Setophaga pinus).

The early warbler with a rich trill.

Voice of the Wild is a podcast about wildlife and the wild sounds they make.

The following Cornell Lab | Macaulay Library recordings were used in this episode:

Sources and more:

https://www.allaboutbirds.org/guide/Pine_Warbler
https://www.audubon.org/field-guide/bird/pine-warbler
Dobson, C., Kassenbaum, D., Oehmke, D., & Misewicz, M. (2023). Field guide to hotspots and birds in Illinois. Scissortail LLC.
Godfrey, M. A., & Kaufman, Kenn. (Directors). (2004). National Audubon Society videoguide to the birds of North America [Video recording]. In Audubon videoguide to 505 birds of North America DVD I & DVD II (Fullscreen.). Godfrey-Stadin Productions.
Peterson, R. T., & Peterson, V. M. (1980). A field guide to the birds: A completely new guide to all the birds of eastern and central North America (Fourth edition, completely revised and enlarged.). Houghton Mifflin Company.
Sibley, D. (2016). Sibley birds East: Field guide to birds of eastern North America (2nd ed.). Alfred A. Knopf.
Stokes, D. W., & Stokes, L. Q. (204 C.E.). Stokes Field Guide to Warblers (2nd ed.). Little, Brown and Company.
Walton, R. K., & Lawson, R. W. (1989). Birding by Ear: Eastern/Central [Compact Disc]. On Eastern/Central birding by ear. Houghton Mifflin Co.