The song of several sparrows and warblers is a trill. To tell them apart note the length of the trill, if it is steady or accelerating, on one pitch or rising, and if there is a distinct final note.
Black and white warbler
Trill formed with couplets
![](http://www.explorebirdsong.org/wp-content/uploads/2023/04/baww_041816_HangingRock_ed2.jpg)
Chipping sparrow
mechanical, 2-3 second trill
![](http://www.explorebirdsong.org/wp-content/uploads/2023/04/chsp_040820_stout_1song-1.jpg)
Field sparrow
Accelerating trill
![](http://www.explorebirdsong.org/wp-content/uploads/2023/04/fisp_051121_LongCreek.jpg)
Pine warbler
Musical 1.5-2 second trill at one frequency
![](http://www.explorebirdsong.org/wp-content/uploads/2023/04/piwa_042323_LongCreek_ed.jpg)
Northern parula
Rising trill ending with a separate zip note
![](http://www.explorebirdsong.org/wp-content/uploads/2023/04/nopa_051121_LongCreek-1.jpg)
Prairie warbler
Rising trill sometimes ending in a buzz
![](http://www.explorebirdsong.org/wp-content/uploads/2023/04/prwa_042421_LongCreek2.jpg)
Swamp sparrow
Irregular musical trill all on one pitch
![](http://www.explorebirdsong.org/wp-content/uploads/2023/04/swsp2041023_LongCreek_crop-1.jpg)
Worm-eating warbler
Very fast unmusical trill lasting about 2 seconds
![](http://www.explorebirdsong.org/wp-content/uploads/2023/04/wewa_042723_HangingRock_ed2.jpg)