Hermit crab wood and stone are used by some species). The tip of the hermit crab's abdomen is adapted to clasp strongly onto the columella of the snail shell. Most hermit crabs are nocturnal. Hermit crabs can be divided into two groups: As hermit crabs grow, they require larger shells. Since suitable intact gastropod shells are sometimes a limited resource, vigorous competition often occurs among hermit crabs for shells. The availability of empty shells at any given place depends on the relative abundance of gastropods and hermit crabs, matched for size. An equally important issue is the population of organisms that prey
Hermit (hummingbird) very decurved bills. Many species, including the rufous-breasted hermit, also use the heliconias for nesting, attaching their conical nest to the underside of one of the plant's broad leaves. The taxonomy of some groups has changed significantly in recent years. Apart from those issues discussed at "Phaethornis", a taxonomic problem occurs with the "Threnetes leucurus"/"T. niger" complex. Schuchmann & Hinkelmann (1999) considered the sooty barbthroat a melanistic variant of the "T. leucurus", but as it was described first, its scientific name was adopted for the entire species; pale-tailed barbthroat ("T. niger"). This, however, has not been accepted by all authorities,