Most pairs holding territories are after-second-year individuals (i.e. in at least their third summer of life), though in a few instances second-year males and/or females had formed pairs on a territory. Some males in their first fall established small territories and maintained them into at least March, but it is unknown if they successfully bred. Due to the high survivorship of most adult males (the majority caught a year or two earlier were still on their territories; unpublished data), it is likely that most males do not get to breed in their second summer.
Most after-second-year individuals banded in the fall of 2010 were still on their territories in the fall of 2012. Thus, individuals can live at least 4 years.
Known causes of mortality are predation by raptors; individuals by roads may be hit by cars.
Thick-billed Vireo is one of the most common resident species throughout its range: they were the most common on Eleuthera (Currie et al 2005b); the fourth most common overall and the most common in broadleaf habitats on Central Andros (Currie et al. 2005a). They have an estimated density of 3 birds/km2 on Grand Bahama and 4 birds/km2 on Andros Islands in pure pine forest (Emlen 1981).
Two species of parasites have been noted. Small mites have been seen on some individual's flight feathers and head feathers, ranging from just a few mites to dozens. An unidentified species of louse has also been collected from a few individuals; one male had at least half a dozen crawling through his breast feathers.