Demography and Populations

Little is directly known about population status or demography. The sex ratio is unknown, nor are there any data on survivorship. The Vervain appears to be common and widespread in human-altered landscapes, and one of the more common species detected on point-count surveys (Latta et al. 2003). It is also potentially undersampled in surveys. This is because, other than the song of territorial males, this species is small and inconspicuous, it does not readily visit feeders (CJC), and is too small to be caught readily in mist nets with a mesh size of 30 mm and larger (S. Koenig pers. comm.). 24 mm mist nets do an adequate job of catching them; although, using these nets, roughly 10 Red-billed Streamertails (Trochilus polytmus) were caught for every Vervain in 2004 and 2005 (CJC).

Wetmore and Swales (1931) suggest that they show altitudinal movements, such as in winter, when food availability may be limited at high elevation. Other species of hummingbird species will exhibit movement such as altitudinal movements that track resource availability, and accounts of the Vervain’s abundance in some locations may be the result of such movements (Wetmore and Swales 1931).

Population regulation

Very little information is available. Because they are so agile, predation may not be a significant cause of adult mortality, and no information is available about nesting success, or recruitment, nor on factors like disease or parasites. During a hurricane, individuals disappeared from their territories in the Blue Mountains for a few days (CJC), and food (e.g., undamaged flowers containing nectar) may be difficult for birds to locate during severe weather. Therefore the population might be food-limited, either episodically (such as during a hurricane), or perhaps seasonally.