The bushtit (Psaltriparus minimus) is a small bird that belongs to the order Passeriformes and is native to Western North America from southwestern British Columbia to Mexico, making its range extremely large. Although it is an uncommon visitor in the Eastern United States, its common range extends as far as western Texas. This is considered its year long range because it does not migrate; although during the winter, the bushtit moves from high to low altitudes and goes back to high altitudes in the summer. The bushtit is the only New World representative of the long-tailed tits (Aegithalidae) family (Sloane 2001). Although it primarily inhabits wetlands, pastures, and shrubbed areas, its habitat can vary from coniferous and deciduous forests to suburban areas with parks (Seattle Audubon 2016).
Adult bushtits are 70-80 mm long, black-beaked, with a gradient gray body and a brown-capped head that varies in coloration by region (Sloane 2001).Males are slightly larger than females and the sexes are easily distinguishable from one another because females have yellow irises while the males are brown. The females’ irises develop from gray when first born and can be differentiated from male after about 30-46 days. Based on location, juvenile male bushtits occasionally have bands of black around their eyes that form a mask. Besides this feature, juveniles are similar in appearance to adults.
P. minimus has a weak flight and can fly only short distances, reaching 200 m at most (Sloane, 2001). They hop when foraging and their diet consists mainly of small insects such as leaf and tree hoppers, beetles, and ants, although they will sometimes eat berries or seeds. Being very agile and active, they often hang from branches to reach food sources. The bushtit is diurnal and is highly social, living in stable flocks of around 10 to 40 individuals. They huddle together with other bushtits during resting periods and cold nights. Due to their social behavior, they are not particularly territorial, and while they become more secluded from the flock during breeding season, they are never isolated (Kaufman 2018).
The courtship of bushtits consists of males pursuing females. When chasing the females, males utter soft contact calls and peck near the female’s tail base to get their attention. Bushtits have a unique nesting process in which members of the flock, mainly adult males, help as nest supernumeraries to build nests that are not their own (Sloane 2001). They have a distinctive hanging nest with an oval pouch which is made of spider webs, branches, lichens, and other foliage, with a small entrance hole at the top (All About Birds 2018; Kaufmann 2018). Clutch size averages 6.3, but this is notoriously difficult to monitor due to the elaborate nest. Both males and females incubate the eggs for about 12 days, with 2 broods per year, and the young leave the nest at about 18 days of age. Hatching, life expectancy, and reproductive success is under-reported because of the difficult access to the nest. However, it has been noted that bushtits regain their social behaviors after becoming more solitary during primary breeding and nesting stages and collaboratively raise juveniles. Predation is the main cause of mortality. Bushtit fledglings are targeted by snakes, climbing mammals, and more aggressive birds during breeding seasons (Sloane 2001).
The bushtit population is categorized as of “least concern” by the IUCN, with the population noted as stable (IUCN 2018). P. minimus has adapted well to living in suburban areas, so their population has not been significantly impacted by human development, but their populations and density do fluctuate locally (Sloane 2001). Reported threats include weather changes affecting nesting behaviors, predation, and insect availability.
