Setophaga ruticilla primarily uses vocal and visual forms of communication. Male Setophaga ruticilla give distinctive songs which are used to defend territory or attract mates. Songs of this species are highly variable but are generally rapid and high pitched. Songs may repeat the same 1 or 2 phrases or have 2 to 8 different phrases given in rapid succession. Some songs end in an accented, terminal note while others simply end unaccented. Setophaga ruticilla uses these different song types to communicate in different situations. Repeated songs with accented endings are typically used for attracting mates, or while males are in close proximity to their mates. Unmated males usually use only this song type. After males secure a mate, they then switch to singing serial songs to defend their territories against neighboring birds. Like many birds, a significant amount of song variation is due to local dialects. Many Setophaga ruticilla individuals can be identified by distinct characteristics of their song such as pattern, frequency, or distinctive syllables. Males of this species can quickly learn the songs of neighboring rivals and incorporate them into their own songs, leading to unique neighborhood dialects.
Setophaga ruticilla also uses body postures and movements as communication. During courtship, males will often chase potential mates in a somewhat aggressive manner and interested females will respond by flying a short distance, then giving a tail-spreading display. Males often give two types of displays towards females: fluff displays and bows. Fluff displays consist of fluffing the body feathers, particularly the bright orange flanks. There is evidence that brighter orange flanks correlate to higher levels of male parental investment, and raising these feathers may serve to advertise parental quality. Bow displays are typically given later in courtship, when a male sleeks his feathers, lowers his breast to the ground, and holds his head vertically.
This species is highly territorial year-round and employs song, body postures, and aerial attacks to deter intruders. As discussed above, males often advertise territory boundaries through singing, but females also give a variety of chips and short notes towards intruders. Both males and females assume threatening body postures including head-forward displays with drooping wings and bill agape, and tail-spreading displays with tail held near vertically. Males also give a wings-out display where they raise and spread their wings, likely to display the orange wing patches. Males also make distinctive circling flights during territorial disputes. Two neighboring males (occasionally females) will alternate short, deliberate, circling flights in pursuit of each other.
Like most birds, Setophaga ruticilla perceives the environment through auditory, visual, tactile, and chemical stimuli.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Setophaga ruticilla is listed as least concern by the International Union for Conservation of Nature and Natural Resources (IUCN) an account of its wide geographic range and relatively stable population size. Recent population data however, has shown this species to be in slight decline and numbers should be monitored closely in the future. Like many declining Neotropical migrants, this species likely suffers from habitat loss on both the wintering and breeding grounds. The main causes for habitat loss is logging for human conversion of land to urban or residential areas. Setophaga ruticilla also prefers shrubby, early-successional habitats which naturally age and progress to mature forests which are less suitable. This species also suffers significant fatalities from impacts with man-made structures during night migration. Over four fall migrations, two towers in Florida accounted for over 1,600 Setophaga ruticilla deaths. Setophaga ruticilla is also a common host for brown-headed cowbirds which decrease reproductive success. Currently, there are few conservation efforts being made for this species, as it is still of least concern. In general, efforts are being made to create sustainable logging practices that support the creation of early-successional habitat. Sustainable farming practices, such as shade-grown coffee, are becoming more prevalent on Central and South American countries that strike a balance between agriculture and providing habitat for songbirds. Many local Audubon chapters are promoting "lights out" campaigns that work with businesses to turn lights off in large skyscrapers during peak migration season, which reduces migrating bird collisions and fatalities.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
There are no known adverse effects of Setophaga ruticilla on humans.
Setophaga ruticilla is a common visitor to shade-grown coffee plantations in Central and South America. These insectivorous warblers are attracted to the ample vegetation provided on these plantations and will consume large amounts of crop pests. This species, along with other insectivores, help to reduce farmer reliance on pesticides.
Positive Impacts: controls pest population
As an insectivore, Setophaga ruticilla consumes significant amounts of insects and likely has an impact on local insect communities. This species also consumes small amounts of fruits and seeds during the fall which may contribute to seed distribution for the plant species it feeds upon. Eggs, nestlings, and adults are consumed by a wide variety of predators. Like many birds, this species is host to several ectoparasites including three lice species and one tick. Setophaga ruticilla is a common host for brown-headed cowbirds and currently will accept and successfully raise cowbird chicks. Populations of Setophaga ruticilla that are exposed to Molothrus ater will react more aggressively to adults than populations that have encountered them less often.
Commensal/Parasitic Species:
Setophaga ruticilla is nearly exclusively insectivorous, but will occasionally consume berries or seeds during the fall when insect abundance decreases. Morphologically, the flattened beak and rictal bristles are similar to old and new world flycatchers (Muscicapidae and Tyrannidae, respectively) and thus these species share similar foraging behaviors and diets. Setophaga ruticilla employs the foliage gleaning method to capture prey and often flicks its brightly-patterned tail to flush stationary prey. Flying prey is then pursued and caught aerially, after which the bird lands on a different perch than it alighted from. Setophaga ruticilla is known for highly energetic foraging habits and is often seen rapidly hopping through all heights of vegetation. It prefers to forage from twigs and branches versus tree trunks or limbs. Overall, this species is a very flexible, opportunistic feeder that can easily adapt to varying habitat, season, insect community, vegetation structure, and time of day. Diet consists largely of caterpillars, moths, flies, leafhoppers and planthoppers, small wasps, beetles, aphids, stoneflies, and spiders. Few berries and seeds are consumed, but are most often from barberry (Berberis), serviceberry (Amelanchier), and magnolia (Magnolia).
Animal Foods: insects; terrestrial non-insect arthropods
Plant Foods: seeds, grains, and nuts; fruit
Primary Diet: carnivore (Insectivore )
Commonly known as American redstarts, Setophaga ruticilla is a Neotropical migrant warbler that spends portions of the year in both the Nearctic and the Neotropical regions. During the spring and summer, Setophaga ruticilla breeds across much of Canada and the United States. It inhabits the southern regions of Canada from the east to west coast. In the United States, Setophaga ruticilla may be found in limited regions of the northern Midwest, and most states east of the Mississippi River. Exclusions include portions of Kentucky, Tennessee, Florida, Georgia, and North and South Carolina. This species migrates biannually across much of the United States and Central America to reach its wintering grounds in southern Central and northwestern South America. Setophaga ruticilla also overwinters on many Caribbean islands including Jamaica and Cuba.
Biogeographic Regions: nearctic (Introduced ); neotropical (Introduced )
Setophaga ruticilla selects varying habitats depending on the season and geographic location. During the breeding season, this warbler inhabits open-canopy, mostly deciduous forests, second growth, and forest edge across much of the United States and southern Canada. This insectivorous bird often shares its foraging habitats with other warblers, and is found feeding in the mid to lower regions of a tree or shrub. Setophaga ruticilla prefers to build its nest well within dense shrubs or the fork of a low tree, and males will select territories that contain several of these potential nest sites.
During migration, Setophaga ruticilla stopover in dense shrubby habitats where food is abundant. On their wintering grounds in Central and South America, this warbler may be found in nearly all woody habitats but tend to avoid non-forested agricultural areas. It is often found in shade-grown coffee plantations which provide native trees and shrubs, as well as coffee trees. Elevations occupied vary by location, as this species may be found at elevations up to 3,000 m in South America, but only up to 1,500 in Jamaica. During the non-breeding season, Setophaga ruticilla is influenced by strong dominance hierarchies that result in sexual habitat segregation. Older males exhibit the most dominant behavior and will occupy preferred, resource-abundant habitats (mangroves). Females and other subordinate individuals are thus restricted to lower quality habitats (scrub), which results in greater mass loss and lower survivorship rates during the non-breeding season. Studies have shown that in preferred habitats, sex ratio is 3:2 (mostly males) while in lower quality the ratio is 1:3 (mostly females).
Range elevation: 3,000 (high) m.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: forest ; scrub forest
Other Habitat Features: agricultural
The oldest Setophaga ruticilla on record was a male banded in adult plumage (making it at least 2 years old) which was re-captured approximately 9 years later, making it at least 10 years old. There is evidence that many females live to be at least 5. Setophaga ruticilla is not kept in captivity and thus there is no data for captive lifespan. Annual survival rates are estimated to be between 50 and 60%. Females are thought to suffer a slightly higher mortality rate as they spend significantly more time on the nest (brooding) and are often consumed by nest predators.
Range lifespan
Status: wild: 10 (high) years.
Typical lifespan
Status: wild: 5 to 10 days.
Setophaga ruticilla is a smaller warbler measuring 13.3 cm in length and weighing 8.3 g. Adult males have mostly black upperparts with bold patches of orange. The sides of breast, bases of wing feathers, and bases of the outer tail feathers feature large patches of bright orange. The belly and undertail coverts are white. Adult females feature the same pattern, but have mostly gray upperparts with patches of bright yellow or orange in older females. They have olive-colored backs and the wings and tail feathers are a darker gray than the head. Throat, belly, and undertail coverts are pale gray to white. First year males closely resemble females and will obtain adult male plumage after the first breeding season. Females and young males may also feature a slight white eye-ring and pale supercillium. All sexes and ages have black legs, feet and bills. The short bill is very similar to insect-eating flycatchers in being relatively flat and surrounded by rictal bristles.
Range mass: 6 to 9 g.
Average mass: 8.3 g.
Range length: 11 to 14 cm.
Average length: 13.3 cm.
Average wingspan: 19.7 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes colored or patterned differently; male more colorful
Setophaga ruticilla is vulnerable to both terrestrial and aerial predators. Highest rates of predation occur during the breeding season when eggs and helpless nestlings are abundant and easy prey for terrestrial predators. Females mostly brood during this period and thus often fall prey to nest predators. Common terrestrial predators include red squirrels, fishers, eastern chipmunks, black bears, flying squirrels, fox snakes, and domestic cats. Aerial predators take nestlings, eggs, or even adults in flight. Possible aerial predators include jaegers, blue jays, common ravens, northern saw-whet owls, common grackles, northern goshawks, and sharp-shinned hawks, and Cooper's hawks.
Known Predators:
Like most warblers, Setophaga ruticilla is predominantly monogamous with rare cases of polygamy. Three stages of courtship have been described: pair-formation, pre-nest building, and nest building. Pair-formation typically begins immediately after females arrive on the breeding grounds. Males aerially chase potential mates, who will only fly a short distance and then perform a tail-spreading display and give harsh chip notes. Once established, pairs will visit potential nest sites within the male's territory. Nest sites are selected by females, and males will closely follow females during this period, presumably to guard them from other males. Males give two main types of displays during nest-building: fluff displays and bow displays. Fluff displays involve raising the feathers on the head and back, while feathers are sleek for bow displays and the male will lower his body to the ground while keeping his head vertical and tail spread.
Mating System: monogamous
Setophaga ruticilla is a Neotropical migrant that travels to North America to breed in the spring. Courtship and pair-formation begins within a week of the arrival of females, which occurs from mid- to late May. After a pair has formed, the female alone selects the nest site which is typically up against a tree trunk, hidden in dense vegetation. The cup-shaped nest consists of tightly-woven, fine materials such as grass, feathers, roots, birch bark, or animal hair. Once the nest is complete, the female lays between 2 and 5 white or cream-colored eggs which are speckled with varying amounts of brown. The clutch is incubated by the female for 10 to 13 days. The young fledge after 9 days in the nest, and may remain with one parent for up to 3 weeks after fledging. First-year males are able to reproduce during their first breeding season, but they retain the female-like plumage which may contribute to low reproductive success (less than 50% of first-year males) until year 2. In contrast, most first-year females successfully reproduce during their first breeding season. There is evidence for a skewed sex ratio that results in a surplus of unmated males.
Breeding interval: American redstarts breed once yearly
Breeding season: The breeding season for American redstarts occurs from mid- or late May through the end of July
Range eggs per season: 2 to 5.
Average eggs per season: 4.
Range time to hatching: 10 to 13 days.
Average time to hatching: 12 days.
Average fledging age: 9 days.
Range time to independence: 3 (high) weeks.
Average age at sexual or reproductive maturity (female): <1 years.
Average age at sexual or reproductive maturity (male): <1 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Male Setophaga ruticilla are very territorial and will actively defend their territories, mates, and young. Females select a suitable nesting site and construct the entire nest alone. Once eggs are laid, females also perform all incubation for an average of 12 days. The young are altricial at birth and thus require significant parental investment. The helpless hatchlings are brooded by the female alone, as the male lacks a brood patch. Both parents participate equally in feeding the young, and each mate makes between 4 and 13 feeding trips per hour. Both parents also remove fecal sacs from the nest to reduce predation and keep sanitary nest conditions. After the young fledge at 9 days of age, each parent typically cares for certain offspring only. The two parents often separate with their respective young, although the male typically stays near the nest site.
One study has demonstrated a correlation between male coloration and level of parental investment. Male Setophaga ruticilla that featured brighter orange coloration on the flanks made significantly more trips to the nest and overall spent more time at the nest. Therefore, male flank coloration may play a role in sexual selection and may explain why first-year males have low levels of reproductive success until they obtain their adult, black and orange coloration.
Parental Investment: altricial ; male parental care ; female parental care ; pre-fertilization (Provisioning, Protecting: Male, Female); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
