The Laysan rail was an opportunist that fed mainly on
invertebrates such as
moths,
Neoscatella sexnotata (
brine flies),
blowflies, and their
larvae; plant
leaves,
seeds, and eggs and carcasses of
seabirds were eaten when they were available. It was an aggressive bird that would fight off other species, particularly the
Laysan finch: the latter is very adept at breaking open seabird's eggs to consume the contents, while the rail was much less so. Consequently, rails would linger around in the seabird colony, be on the lookout for finches which had just cracked open an egg, chase these away, and consume the egg's contents. On
Midway, the rails were seen to steal food from domestic
chicken. There exists no permanent source of freshwater on Laysan, and while the rails must have been able to cover their needs from the body fluids of prey and the content of eggs, they would eagerly drink from and bathe in pools of water remaining after heavy rain, or a pan of water provided by an observer. Although it was flightless, it would use its wings to assist in keeping balance when running quickly and jumping; this way, they were able to make jumps of somewhat less than . They were nimble and restless, retreating to the
tussocks to avoid predators, but chiefly to escape the mid-day heat; if they felt threatened, they often hid in the burrows of
petrels. The birds were most active in the open in the morning and afternoon, but it could regularly be seen all day and heard calling at night. Laysan rails had no natural enemies apart from occasional predation by
frigatebirds; all reports remarked upon its fearlessness, and if an observer stood still, rails would approach and even climb over him to search for scraps of food. One bird, removed from its nest in an attempt to photograph the eggs, would immediately return to protect her clutch. The species was somewhat territorial, more so during the breeding season. On Laysan,
carrying capacity was reached at of habitat per bird, while on Midway, population density was one-fourth of this figure; in captivity, an enclosure of roughly was sufficient for two pairs, but introducing more birds into this space would lead to fights.
Vocalization When active, Laysan rails would ever so often stand still and utter one to three soft warbling chirps. In courtship or territorial defense (reports are not clear, but probably the latter) two birds would stand opposing each other, fluffing up their plumage, and give rattling, scolding calls not unlike a mechanical
alarm clock. Soon after dusk, the entire population could be heard to engage in a brief bout of vocalization, which Frohawk (1892) described as sounding like "[...]a handful or two of marbles being thrown on a glass roof and then descending in a succession of bounds."
Downy young would vocalize a lot, and their calls were rather loud in proportion to their tiny size.
Reproduction On Laysan, courtship and the start of nest-building was in April, with eggs being laid from May to June and the height of the nesting season taking place in June and July; there is a report of recently hatched young birds from Midway in March, but this seems to be unusually early. On Laysan, nests were built in tussocks of endemic
Cyperus pennatiformis subsp.
bryanii,
kāwelu (
Eragrostis variabilis) and introduced Bermuda grass (
Cynodon dactylon) around the lagoon, while on Midway, it nested in any shelter that seemed convenient, such as
naupaka kahakai (
Scaevola taccada ) thickets and
pōhuehue (
Ipomoea pes-caprae subsp.
brasiliensis) stands. The nests were placed on the ground or inside the base of a tussock; in the latter case the birds would rearrange the dried dead leaves to form a roofed cavity reached through a small tunnel some long. Nests were lined with soft dried plant material and
down of seabirds. The
clutch consisted of 3 or less frequently two eggs (as opposed to some 5–10 for related continental rails). These were oval without being conspicuously more rounded on one end, measuring 31 x 21 mm and being pale olive buff in base color, irregularly marked all over in pale
raw sienna or purplish grey. The sexes mated either for life or for an entire breeding season and shared incubation duties, although females seem to have spent more time incubating than males. The young hatched after approximately 20 days of incubation (perhaps somewhat less; in related species it is usually 16–20 days) and were tended for by both parents for about one month. Five days after hatching, the young were able to run as quickly as adults. Hadden (1941) described a three-day-old chick as follows: "A black velvet marble rolling along the ground. Its little feet and legs are so small and move so fast that they can hardly be seen." ==Extinction==