Nocturnal and highly gregarious (Snow 1961, Hilty and Brown 1986, Hilty 2003). They gather in large numbers in caves and when foraging (Hilty and Brown 1986, Hilty 2003). The largest colony is estimated at 10.000 individuals, in PN Cueva del Guácharo in Venezuela (Bosque 2002). Some populations migrate seasonally to regions remote from breeding cave in search for food. Oilbirds navigate through echolocation (Griffin 1953). Roosting sites in the forest are not the same place that the birds forage, which indicates that they are effective seed dispersers (Holland et al. 2009). Birds forage up to 75 km from their roost and forage 120 km from the cave nightly (Holland et al. 2009). Recent studies have shown that individuals do not continuously fly throughout the night and do not return to the cave nightly, but make extended foraging trips over a number of nights (Holland et al. 2009). Whenever birds stay outside the cave, they roost in trees in the forest during daylight hours. While roosting in the cave, birds maintain a significantly higher level of activity compared to that provided while roosting in the forest (Holland et al. 2009). Cave roosting behavior seems to be a trade-off between the benefits of avoiding diurnal predators and the high cost of remaining active (Holland et al. 2009).