A large pipit-like bird that is much less colorful than other longclaws, with a dull pinkish-buff throat, cinnamon-tawny underparts and extensive dense dark streaking elsewhere. During the breeding season the throat and belly may flush brighter pink, and a small white shoulder patch may be visible. Pairs are localized residents, preferring short grass on floodplains and dambos (seasonally flooded wetlands); retreating to wettest habitats where other longclaws co-occur. Calls an extended series of high-pitched trilling or buzzing notes that sound insect-like, different from other longclaws. Similar but smaller Rosy-throated Longclaw differs from Grimwood’s by having a bold black gorget and brighter pink throat and underparts.