Like nearly all hummingbirds, the Vervain is exclusively dependent on flight for locomotion, and uses its feet primarily for preening and clinging to things such as perches, or other hummingbirds during a fight. It is capable of hovering, and females have a hovering wingbeat frequency of 47.5 ± 3 Hz (mean ± s.d. of four birds), as determined using high-speed video (CJC; no data are available for males).
This species tends to forage on small, low-yield flowers, and makes up for quality with quantity. When visiting a large inflorescence of tiny flowers, it can insert and remove its bill from neighboring flowers extremely rapidly (> 1 Hz), reminding one of the head of a sewing machine bobbing up and down (CJC). Compared to other hummingbirds, it licks very quickly (based on observations of feeding hand-held individuals; CJC). A male holding a territory would leave his territory to feed (Clark 2006), and no other evidence of active resource defense (i.e., territorial defense of flowers) has been observed in either sex. The bird often holds its tail cocked up while feeding at flowers (Gosse 1847).
The Vervain preens much like other hummingbirds, utilizing the bill to spread preen oil and manipulate individual feathers; uses the claws to preen feathers on the head (CJC). Like many hummingbird species (and other bird species), periodically stretches the wings and spreads one or both sides of the tail, often at the end of a preening bout (CJC).
See also Sexual Behavior, below. Like many hummingbirds, the Vervain is generally aggressive towards others of its kind, although this species may be somewhat less aggressive than the average hummingbird. At times, two or three individuals (sex unknown) can be seen perched several cm apart on a territorial male’s song perch (CJC).
A curious display, termed ‘competitive vertical ascent’ by Clark (2006), has been reported by several sources (Clark 2006; Downer and Sutton 1990; Smith 1967). The most detailed observations of the behavior are described in Clark (2006), who reports observations taken just after hurricane Dennis (in 2005) swept through the Blue Mountains. A focal male left his territory for four days during the hurricane, and the observations of the behavior took place right after the male returned to his territory, suggesting that, possibly, the competitive vertical ascent occurred as the male was re-asserting his ownership of the territory, with his neighbors. The following description of the behavior is paraphrased from Clark (2006):
Two adult males were silently perched on the main song perch, facing each other about 10 cm apart. Both birds engaged in preening, wiping the bill on the branch they were perched on, and alternated these behaviors with continuous turning from side to side, while perched, in a fashion similar to the “chatter–sway” behavior of the Anna’s Hummingbird (Stiles 1982), except that there seemed to be no vocalizations. This swaying continued for at least 12 minutes, then abruptly one male flew directly at the other bird and they tumbled out of sight, clinging to each other, while producing the ‘scolding’ call (see Vocalizations). Moments later they flew back and landed close together on the song-perch, and then began the competitive vertical ascent (CVA).
In CVA, one bird would take off from his perch to fly straight at the other, and then, close together, both would quickly ascend vertically. At some height, both birds would stop ascending and glide with spread tail and wings back down to the top branches of the tree (i.e., the song perch). Video showed that in 18 of 19 ascents, the birds quit ascending when one bird had risen above the other. The vertical excursions during this behavior ranged from 1 to 10 meters. Sometimes rather than ascending they would fight, (i.e., one would fly at the other, they would make physical contact and fall out of sight, apparently clinging to each other, while one or both emitted a scolding call). The behavior ended when one male abruptly flew away from the territory, after approximately 20 minutes of performing the CVA. The departing bird was not chased by the other hummingbird.
Other authors have interpreted this behavior as a courtship display and indicated that a female was one of the participants, but there are inconsistencies in the other stated accounts, such as Smith’s (1967) indication that both individuals had white in their tail. If this was true, however, the presence of this character would indicate that neither bird was an adult male, and that therefore the display would be unlikely to be a courtship display. Because the behavior reported by Clark (2006) was clearly performed between two adult males, one of which maintained a territorial song perch at the point of the display, Clark (2006) concluded that the behavior was competitive in nature. This conclusion does not preculde the behavior from also having a courtship function that was unobserved by Clark (2006).
Males hold breeding territories that are similar to the territories held by other male ‘bee’ hummingbirds, such as the Anna's Hummingbird (Clark 2006). The male selects a small area (one territory was roughly 20 x 20 m) and consistently uses the same five to ten perches. Roughly five of these perches are ‘song’ perches, which are prominent, exposed perches, often dead twigs at the very highest point of a tree or bush, 5 to 40 m off the ground, and in the sun. These perches are often very hard to see from the ground. Males spend most of their time on their song perches, and a disproportionate amount of time on just one or two of these perches. Other song perches may be used when other larger birds land near their primary perch, scaring the male away from his primary perch. Males will also sometimes perch in inconspicuous locations, such as the middle of a coffee plant, where they preen or fly-catch but generally do not sing. Neighboring territories in the Blue Mountains appeared to be placed at least 100 m apart (CJC).
Similar to the territories of male Anna’s Hummingbirds, the main territory that Clark (2006) observed did not contain any food plants, indicating that food resources were not necessary to induce a male to maintain a territory. This, and the fact that only males hold territories, suggests that the territory is held primarily for courtship or breeding. Another male was observed visiting flowers close to one of his song perches, however, indicating that males will utilize any flowers that happen to be available on their territory (CJC).
For displays performed on the territory, see agonistic behavior (above) and courtship behavior (below).
It is common for hummingbirds to hold resource-based (i.e., feeding) territories, but this behavior has not been reported for Vervain Hummingbirds.
Only females have been observed making nests and rearing offspring, suggesting that, like in related species, male Vervain Hummingbirds do not provide any care for offspring. Given that male territories also do not appear to contain resources utilized by females, male territories are therefore best considered to represent an ‘exploded lek’, in which males provide only indirect benefits to females. This also predicts that there is high mating skew, with a few males obtaining most of the copulations. Copulation itself has not been reliably described.
In his observations on a territorial male, Clark (2006) saw two related displays (in addition to the CVA described above) that he interpreted to be related to courtship. In the first, the male would rapidly fly in a flat, horizontal circle approximately 10 to 20 m in diameter over the center of his territory. This display was frequently performed in the apparent absence of other birds, but in once instance a variant of this display was seen in which two birds were involved. One bird flew in a horizontal circle approximately 15 or 20 m in diameter, while the other bird followed the first bird, flying in a tighter circle approximately 10 m in diameter but flying slowly enough so as to not overtake the lead bird. One of the birds sang continuously during this behavior, and it is unknown if it was the lead bird or the follow.
The territorial male also performed a display-dive that was similar to dives performed by North American ‘bee’ hummingbirds, and which was an extension of these circular flights. The male ascended 20 to 30 m and flew part of a horizontal circle, then abruptly dove steeply, losing 20 to 30 m of elevation, then pulled up and flew a second horizontal circle at this lower height. At the bottom of the dive he emitted a sound that appears to be vocal due to its exact match with the song (Clark 2006). Two dives appeared to be directed at a human, whereas two other dives may have been directed to an unseen bird that was in the vicinity. The function is interpreted as sexual only because similar dives in related species are also thought to be courtship displays.
Social and interspecific behavior
Like all hummingbirds, Vervains do not appear to be social, although at times up to three individuals can be seen perched near each other on a male’s song-perch (CJC). When wild individuals were temporarily caged with Red-billed Streamertails (Trochilus polytmus), the latter is somewhat aggressive towards Vervain Hummingbirds, suggesting that the two species may also interact agonistically in the wild (CJC).
This species is bold and unafraid of humans (Gosse 1847), and will readily attack much larger species of birds, including Mockingbirds (Wetmore and Swales 1931), American Kestrel (Falco sparverius) and Mangrove Cuckoo (Coccyzus minor) (C. Levy pers. comm.) especially if these predators come near a nest. Lizards may also be attacked for the same reason (Paterson 1973).
Likely to be taken opportunistically by a range of predators, if they are lucky enough to catch a Vervain. In one instance, a female Vervain attended to a nest that was right next to a Brush-footed spider’s (Nephila clavipes) web. The female was caught in the web and died, apparently because the spider bit and killed her (Levy 1987; Tyrrell and Tyrrell 1990).
Unidentified mites were found on the rectrices of one individual in the Blue Mountains (CJC); these seemed similar to the mites common on Anna’s Hummingbirds’ rectrices in the population in Berkeley, CA (CJC). There did not appear to be any damage on the rectrices associated with the mites, which suggests that they might eat skin or dander, and not the rectrices (CJC).