Lapland Longspur, like Rough-legged Hawk, is refreshing in that it is an Arctic nester and the STEM animation shows it returning to the Lower 48 for the winter. A grassland bird, it can occur in flocks of thousands or tens of thousands in the Great Plains (e.g., the Texas Panhandle), but in many areas it flocks are much more modest.
Like Rough-legged Hawks, Lapland Longspurs can be found almost across the country and in almost every state, although (like Rough-leggeds) they are absent or very rare in the southernmost regions. Also like Rough-leggeds, the scale on these maps is very low, indicating that the overall likelihood of encountering a “Lap” is pretty low. Part of this is due to the habitats that they use: wide open fields that may seem birdless, unless you are lucky enough to see a big flock of larks or longspurs flush from it. Few birders walk through these barren expanses, and if more did, we’d surely have many more longspur reports.
This animation gives a nice wide-angle view of where most longspurs go. Sure, birders in southern California, Maryland, and northern Alabama know exactly what fields these birds prefer and how to go seek them out. But compared to the large numbers that use Kansas, Oklahoma, and north Texas in winter, these small, local flocks are a mere drop in the bucket of the overall population. Your field guide range map (or the eBird map) can give a good sense for the extent of the range of a bird like a Lapland Longspur, but these STEM maps (which are less good at showing the outliers) are unique in their ability to accurately show the core of the species’ range. Compared to the central Great Plains, those outliers are not even on the same scale. (Even still, notice how STEM does pick up the exact area on Maryland’s Upper Eastern shore where longspurs can be found.)