Horned Lark is a dapper denizen of North America’s driest and most barren terrain. They breed on the ground in almost any wide open treeless areas, including beaches, deserts, vast agricultural fields, shortgrass prairies, arctic and alpine, tundra and airports. It is also one of the most diverse species not just in the United States but around the world, with some 44 subspecies worldwide (29 in North America). This diversity in habitat preferences and in different populations makes the animated occurrence map seem like a difficult thing to interpret.
As one of the most common birds in the Great Basin and Great Plains, the high occurrence there essentially swamps out the detail that might otherwise have been visible in the East and along the Pacific Coast, where the species is much more locally distributed. The common tale of northward and southward migration is not so obvious here, even though the flocks of prairie-breeders are augmented by tens of thousands of Arctic breeders which arrive for the winter. For this species, more than for many, this map might look quite different if it displayed abundance (i.e., counts of birds) rather than just occurrence (i.e., presence/absence).
Even still, some broad patterns comport well with the species biology and are listed below in no particular order:
- Notice how clearly some extensive areas of agriculture show up on the maps: the central Mississippi River Valley (e. Arkansas, ne. Lousiana, and w. Tennessee), northern Indiana and Illinois, and south Texas just north of the Rio Grande are three such examples.
- The few patches in the East that do show up also match up to agricultural areas where open country provides good lark habitat. The central Delmarva Peninsula, some of the East Coast beaches, and farming areas in New York and southeast Pennsylvania can all be easily identified.
- In the West the picture is similar, with the Central Valley of California and the Willamette Valley of Oregon fading in and out of view at various times of the year.
- Most mountain areas are forested ad thus do not show Horned Larks, but some of the “parks” (broad valleys) in Colorado show up as areas where Horned Larks occur. At finer scale, the mountaintop breeding birds might show up, but since these patches are so tiny, they are lost on these maps which show distribution at the 30 km scale. Stay tuned for 3 km scale maps which may show this better!
- General northward movement in March and southward movement in October to December. Horned Larks are somewhat facultative migrants so may move about throughout the winter in response to weather conditions.