New Code Uses for Two Species at Risk

Kevin Hannah, Environment and Climate Change Canada.

May 2024

New research gives us the evidence we need to elevate breeding evidence codes for two species at risk in certain situations.

Grasshopper Sparrow

Explanation: Male Grasshopper Sparrows sing two distinct types of songs. The primary “buzz” song is generally sung more frequently earlier in the breeding season and consists of 3-4 introductory notes followed by a long trill. The buzz song, often paraphrased as “tip-tup-a-zeeeeeee”, is generally less than 2 seconds in length. The extended “warble” song is only sung by males that are paired with a female and consists of numerous variable notes, often repeated two or more times in rapid succession. The warble song is generally much longer in length than the buzz song, lasting anywhere from 5-15 seconds.    

Summary: Singing males would be assigned the “possible” breeding evidence code “S” when a singing male is detected in suitable nesting habitat singing the buzz song. Since male Grasshopper Sparrows only sing the warble song when paired with a female, then the “probable” breeding evidence code “P” can be used to designate that a pair was detected.

Both breeding codes only apply during safe breeding dates.  

(In this recording, the buzz song is given, followed by the warbler song in close succession)

Common Nighthawk

Explanation: Male and female Common Nighthawks use a vocal “peent” call in flight, both during migration and on the breeding grounds. Male Common Nighthawks also make a non-vocal “boom” sound that is produced by air rushing through feathers in a sudden downward flexing of wings during a steep aerial dive. These boom displays are generally only associated with mating and territorial displays and do not occur outside of the breeding season. The peent call by itself provides no indication of breeding, but it is the more common way that this species is identified in the field. The boom sound is generally used to define the boundaries of a breeding territory and when performed repeatedly (e.g., greater than 3 times in a 5-minute period) can indicate a nest.             

Summary: Birds detected visually or heard using the peent call can be assigned a possible breeding evidence code “H”, when detected in what appears to be suitable breeding habitat (e.g., logged or burned areas, rock outcrops, clearings, etc.). When booms are detected, but are occurring in the air or not frequently happening close to the ground, the probable breeding code “D”, which is indicative of courtship or a breeding display, can be used. If booms are happening frequently near the same location on the ground, the probable breeding code “V” can be used to indicate a bird visiting a probable nest site. All breeding codes only apply during safe breeding dates.

(In this record a single bird is giving peent calls and one boom can be heard at the same time as the third, or second-to-last, peent).


Brigham, R.M., J. Ng, R.G. Poulin, and S.D. Grindal. 2020. Common Nighthawk (Chordeiles minor), version 1.0. In Birds of the World (A.f. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.

Knight, E.C., R.M. Brigham, and E.M. Bayne. 2022. The Big Boom Theory: The Common Nighthawk wing-boom display delineates exclusive nesting territories. Ornithology 139:1-10.

Lohr, B., S. Ashby, and S.M. Wakamiya. 2013. The function of song types and song components in Grasshopper Sparrows (Ammodramus savannarum). Behaviour 150:1085-1106.

Vickery, P.D. 2020. Grasshopper Sparrow (Ammodramus savannarum), version 1.0. In Birds of the World (A.F. Poole and F.B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA.

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