Horned Larks have a variety of calls which include chi-dit, seerp/tseep, and buzzy calls. They are used on the ground and as flight calls.
The following recordings were made of wintering birds in Lancaster County, PA in February.
Chi-dit calls are highly variable, each call usually being different from those preceding or following, indicating a large repertoire.
Another example of chi-dit calls. Some of the lower calls of American Pipits can sound similar.
Interestingly chi-dit calls appear to be a component of the Horned Lark song.
The next category of calls are the seerp/tseeps, which vary in length, can be modulated, may be multi-syllabic, and are mostly descending.
see-der (first two calls).
Two tseeps followed by seerps.
Call by a bird taking flight.
Buzzy call (first call, followed by chi-dit and seerp).
Calls in flight by a disturbed flock of about 30 birds. Mostly chi-dit and buzzy calls.
Two birds displaying face to face, and then fighting in mid-air at 47-60 sec.
Edited sonagrams of the chi-dit calls in this recording, showing the variety and frequent repetition of the notes, indicating a large but finite repertoire (time scale reduced).
American Pipit in flight. There are two basic call types, a higher, often doubled call, and a lower call (with Purple Finch, Nov, PA).