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American Robin

Turdus migratorius

Order:
Passeriformes
Family:
Turdidae
Sections

Behavior

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Locomotion

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In flight, American Robin has several smooth wing beats interspersed with a short glide when wings are held close to the body.

© Brian Sullivan, California, United States, 7 January 2016

Walking, hopping, climbing, etc.

Running is well developed; on the ground, usually makes a short, straight run with rapid steps, pausing frequently to scan for prey and/or predators. Will hop if vegetation is too long to permit running. Does not climb.

Flight

Short, low flights are common. Need more information.

Swimming and diving

Does not swim.

Self-Maintenance

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American Robin regularly visits backyard bird baths, but will also bathe in rain puddles and other fresh water sources.

© Jay McGowan, New York, United States, 28 February 2016

Preening, head-scratching, stretching, bathing, anting, etc.

Preening movements such as scratching, reaching, head-rubbing, and feather-fluffing and -shaking are common and similar to those of other passerines. Preening is most common at times of day when other activities are reduced and during the molt period. Scratches head over the wing. Stretching may be lateral, leg extended back and same side wing in full extension, tail spread; or both legs straightened with upward extension of both wings with only the primaries spread. Bill-wiping occurs from base to tip, usually on a branch while perching (RS). Bathes in shallow portions of streams and ponds, in temporary puddles and even lawn sprinklers, as well as bird baths (Bernard 1981). Bather wades into water until belly is submerged, dips forward while fluffing breast feathers, lowers and flutters wings, wetting them and splashing water over back and tail. Repeats splashing sequence several times. Bather then shakes off water and flies to nearby perch to preen. Anting observed in Kentucky (P. K. Eason pers. comm.)

Sleeping, roosting, sunbathing

Sleeping behavior not documented.

Roosting is common, especially during the nonbreeding season; spring and summer robin roosts documented by Brewster (Brewster 1890d), Howell (Howell 1940), and Eiserer (Eiserer 1980c). The consensus appears to be that robin roosts are attended by all birds during the winter months, by adult males during the breeding season, by adult females once nesting is completed, and by offspring of both sexes as soon as they can negotiate the trip to the roost. Communal robin roosts have been estimated to be as large as 250,000 birds (Black 1932); mixed-species roosts (e.g., with European Starlings [Sturnus vulgaris] and Common Grackles [Quiscalus quiscula]) are known to have exceeded 100,000 birds (Morrison and Caccamise 1990), although are typically smaller (Ulmer 1990). More typical roost sizes are on the order of 20–200 birds (Walsberg and King 1980, RS). In Minnesota, robins arrive to roosts one hour before sunset, often in groups of 30, reaching roosts of at least 2,300 birds (Bell 2010).

Robins studied in New Jersey from Jun to Nov 1987 were found to roost within 3 km of their “diurnal activity centers” (DACs), but sometimes shifted to new DACs 7–9 km away at the end of the breeding season (Morrison and Caccamise 1990). Roost-switching (i.e., using a roost that is different from the one used the previous night) occasionally occurs (12% of the time; Morrison and Caccamise 1990), but only rarely do birds switch to roosts >2 km away. Nocturnal winter roosting probably provides both foraging and antipredator benefits (Morrison and Caccamise 1990) rather than a thermoregulatory benefit (Walsberg and King 1980). “Roosttime restlessness” is known to occur in captive robins (Eiserer 1979) and first appears at the age when a young wild robin would be expected to make its first visit to the roost (Eiserer 1980a).

Sunbathing has been documented (Tyler 1949a, Goodman 1983) and may be especially important during freezing winter periods when robins are feeding exclusively on fruit (Sallabanks 1997). During the breeding season, individuals move into sunny spots in mid-and late-afternoon, often on mowed fields and lawns where available. To sunbathe, robins lower themselves to the ground, and spread their wings out and fan their tails slightly to moderately. Usually crouch with neck arched and head turned so that they are looking over their shoulder. Often sunbathe in pairs (P. K. Eason pers. comm.).

Daily time budget

Few data. Most data pertain to foraging behavior (see Diet and Foraging: Feeding). Most time (approximately 75%) is spent perching or standing quietly; remainder divided relatively equally among flying, hopping, feeding, maintenance, and singing (Ferguson and Ludwig 1991). Daily activity budget of wild individuals is not significantly different from that of captive-reared birds (Ferguson and Ludwig 1991).

Agonistic Behavior

Physical interactions

Males are more aggressive than females and initiate more and spend more time on aggressive interactions when they have fertilizable mates (Hsu 1992). Males are aggressive to keep other males away from their mates rather than to gain control of resources needed by females in order to attract them (Hsu 1992). Documented interactions are rare. Aggressive posturing includes crouching and lifting the tail often followed by charges. Aggressive interactions can follow and consist of jumping and wing flapping (ENV). Wing drooping and chest fluffing can also occur before or after interactions (Stokes 1979, ENV). When foraging on earthworms, robins vigorously contest worm-stealing by conspecifics with sharp vocalizations and leaps into the air (Bird et al. 1973); individuals with large worms will also charge nearby conspecifics, aggressively driving them away, presumably to anticipate an attempt at stealing. When threatened with losing a worm to other species (e.g., starlings), however, robins typically flee.

Communicative interactions

More information needed; no known records of appeasement displays. Males intimidate each other through actions such as running toward one another in a crouched posture or chasing; subtle dominance may be established by “pushing” a retreating rival with short run-and-pause movements (ENV). Known to exhibit a distinctive “wing-droop” aggressive stance when threatened (Sharp 1990).

Spacing

Territoriality

Breeding territory size varies inversely with population density: 0.11–0.21 ha in New York (n = 33 pairs; Howell 1942), 0.04–0.24 in Wisconsin (n = 34 pairs; Young 1951), and 0.12–0.84 in Tennessee (n = 62 pairs; Pitts 1984). Territories established and maintained by males using a combination of song and aggressive displays. During male territorial establishment, testicular weight increases rapidly though no developing sperm occur; females experience little increase in gonadal weight and maintain winter sociality of flocking behavior (Kemper and Taylor 1981). Males intimidate each other through actions such as running toward one another in a crouched posture or chasing; subtle dominance may be established by “pushing” a retreating rival with short run-and-pause movements. Known to attack reflections in windows (ENV).

Degree of territoriality may also vary with population density; as density increases territoriality may decrease. In Illinois little territorial behavior was observed and robins did not respond to playbacks or decoys (Rowe and Weatherhead 2007). Similarly, in Kentucky little territorial behavior was observed, and playbacks and decoys did not increase mist netting of male robins (ENV). No indication of interspecific territoriality during the breeding season. No information on dominance hierarchies.

Winter territoriality occurs primarily in the form of fruit defense (Young 1956, Holtz 1980, Pietz and Pietz 1987, Sallabanks 1993a). Pietz and Pietz (Pietz and Pietz 1987) observed 1 robin defending a fruit-bearing crab apple tree against up to 15 Cedar Waxwings. Defense of the tree against larger flocks was unsuccessful. Sallabanks (Sallabanks 1993a) compared the foraging behavior of robins defending English hawthorn bushes with that of conspecifics intruding on defended territories. Territory owners had longer feeding bouts, ingested more fruits per bout, and foraged for fruits more slowly than intruders. During the first minute after arrival at a fruit source, intruders attempted to pick fruits almost 3 times as fast, and ingested twice as many fruits, as territory owners.

Individual distance

Although no specific information, presumed to maintain about 1 body length individual distance in flocks; more in feeding aggregations on the ground (Kemper 1971). Fledgling robins remain close to parents for several weeks, often following parents and emitting begging calls (ENV).

Sexual Behavior

Mating systems and sex ratio

Socially monogamous. Information on sex ratios unavailable. More data needed.

Pair bond

Generally socially monogamous throughout the season; rematings in successive years most likely due to chance (Young 1955). Mate choice based on plumage; both male and female robins tend to choose mates that are similar to themselves in regards to breast color (positive assortative mating; Rowe and Weatherhead 2011). Copulation follows dawn singing and a strutting courtship display by the male around the female on the ground (Audubon 1841 cited in Tyler 1949a), during which he spreads and elevates his tail, shakes his wings, and inflates his throat (Howell 1942). Also associated with pair formation is Ceremonial Gaping, whereby male and female approach one another and touch (or nearly touch) widely opened bills (Young 1955). Courtship feeding may also occur. Mate guarding observed in New York; male remains close to female and copulates daily until clutch is complete (Gowaty and Plissner 1987). Mate guarding may have little impact in some populations in which female may choose to remate with male based on his paternal care (Rowe and Weatherhead 2007).

Extra-pair copulations

Rowe and Weatherhead (Rowe and Weatherhead 2007) documented high levels of extra-pair copulation (EPC) in robins; data from two breeding seasons in Illinois indicate that between 62% and 72% of broods contained at least one offspring from an EPC and up to 48% of offspring were the result of an EPC. High breeding densities and lack of territoriality may have contributed to the high levels of EPC. Extra-pair paternity was lower in second broods when the interval between clutches was shorter, indicating that female robins may prefer to remate with males that are good parents and able to take sole responsibility for the first brood, thus allowing her to dedicate her resources to the next brood (Rowe and Weatherhead 2007).

Social and Interspecific Behavior

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American Robin is gregarious during during fall and winter, often occurring in large communal roosts at night and feeding in flocks where fruit resources are plentiful.

© Brian Sullivan, California, United States, 7 January 2016
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In winter, American Robin shifts to a diet of mainly berries. Here a group feeds on juniper berries.

© Doug Swartz, Colorado, United States, 4 February 2016

Degree of sociality

Loosely gregarious during the breeding season; more tightly gregarious in the nonbreeding season. Flocking during winter months increases foraging success in competitive encounters over fruit supplies with other species (Moore 1977). Under extremely cold winter conditions, known to improve foraging efficiency by defending fruit supplies against conspecifics as well as other species (Sallabanks 1993a). Young fledglings also join feeding flocks of adults to forage on fruit sources near their nest (Hirth et al. 1969); flocks remain intact until fruit supply is exhausted. Published studies report feeding flock sizes of 2–50 (Chavez-Ramirez and Slack 1994), but feeding flocks can be much bigger (>250; RS). Roosting flock sizes are known to be much greater (see Behavior: Self-Maintenance). The “loose” flock structure of robins (i.e., high spacing among individuals and individual movement to and from foraging sites) improves their efficiency as seed dispersers, as seeds are “scattered” widely among postforaging sites (Chavez-Ramirez and Slack 1994).

The impact of early social experience on later ability to recognize and associate with conspecifics was tested by Schimmel and Wasserman (Schimmel and Wasserman 1991, Schimmel and Wasserman 1994). After 30 d of being raised with a “nestmate” (another individual bird in the nest that was either another robin or a Blue Jay [Cyanocitta cristata]), robins did not discriminate between the nestmate and its conspecific. Furthermore, when given a choice between 2 unfamiliar birds (regardless of species), robins chose the alternative over the nestmate's species. Lack of nestmate preference may be related to the fact that immature robins disperse soon after fledging and forage wherever they find territory unoccupied by conspecifics. Although juvenile robins show no preference for nestmates, in Kentucky they do tend to forage with other juveniles more often than do adults; in late summer and early fall large aggregations of juveniles can be seen foraging together (see Diet and Foraging, Vanderhoff and Eason 2008).

Play

Not known to occur.

Nonpredatory interspecific interactions

Known to compete with other avian frugivores, such as Northern Mockingbirds (Mimus polyglottus) and Cedar Waxwings, for fruit (Moore 1977, Pietz and Pietz 1987, RS). Robins defending fruit supplies are known to chase away other species (e.g., Pietz and Pietz 1987) as well as conspecifics (Sallabanks 1993a). Starlings, American Crows (Corvus brachyrhynchos), Song Sparrows (Melospiza melodia), and House Sparrows (Passer domesticus) steal worms from robins with mixed success (Tyler 1949a, Bird et al. 1973).

On rare occasions, robins have been observed feeding the young of other birds (Chestem 1990). Known to share nest with a Northern Cardinal (Cardinalis cardinalis; Maslowski 1991) and switch nests with an Eastern Phoebe (Sayornis phoebe; Parmelee and Parmelee 1979). One report of a robin killing a Steller's Jay (Cyanocitta stelleri) by penetrating the jay's head with its beak following a fight that included strikes with both beak and wing and pounces with feet (Tyler 1949a). Shedd (Shedd 1982) documented attack behavior on a mounted Screech Owl (Otus asio). Such attacks consisted of short dashing flights, culminating in strikes, usually about the head or neck. Injured robin in Ontario had a porcupine quill in its neck, however unsure if injured from direct contact or secondarily injured (Chubb 2006).

Predation

Predators and manner of predation

In New Mexico, adults are important prey items for Cooper's Hawk (Accipiter cooperii; 11% of diet) and Northern Goshawk (A. gentalis; 6% of diet; Kennedy 1991b). Robins also a prominent prey item of Northern Goshawk in Wyoming (Squires 2000). Adults are also preyed upon by Sharp-shinned Hawk (A. striatus), various snakes, and domestic cat (Felis catus); eggs and nestlings are taken by various snakes, Steller's Jay (Cyanocitta stelleri), and American Kestrel (Falco sparverius) (Bent 1938b, Martin 1979c, Cox 1986).

In Indiana, robins are a preferred food item of Sharp-shinned Hawks during the winter, attacked more often than expected given their abundance (Roth II et al. 2006). In Kentucky, Accipiter spp. are main avian predators of adults (ENV). In Ontario, cats account for a large portion of robin deaths (Chubb 2006). Eggs were found to be punctured or “dented” beneath some nests in Delaware; House Wren (Troglodytes aedon) were the likely cause of such nest failures (Niles 1985). In the Sierra Nevada Mountains of California, Clark's Nutcracker (Nucifraga columbiana) were observed attacking robin nests and on one occasion a nutcracker was successful at removing two of four robin eggs (Morton and Pereyra 2004).

Other major predators on eggs and young in various parts of geographic range include red squirrel (Tamiasciurus hudsonicus) in Minnesota (Yahner 1983c), Maine (Knupp et al. 1977), and British Columbia (Campbell et al. 1997b); rock squirrel (Spermophilus variegatus) in Colorado (Ortega et al. 1997); American marten (Martes americana) and garter snake (Thamnophis sirtalis) on Vancouver Island (Martin 1973e); Common Raven (Corvus corax) in Maine (Knupp et al. 1977); Blue Jay (Cyanocitta cristata) and Common Grackle (Quiscalus quiscula) in Minnesota (Yahner 1983c); house cats in Iowa (Klimstra and Stieglitz 1957) and Minnesota (Yahner 1983c); and Common Grackle, especially in first nesting cycle, in Madison, Wisconsin (Young 1949).

Experiments with taxidermy robin decoys in Illinois indicate that parental attendance is a strong deterrent to depredation and nests with decoys/parents were more likely to be attacked by mammalian predators, like raccoons, than were unattended nests, which were primarily attacked by avian predators (Swanson et al. 2012). In Ohio nest depredation was higher in urbanized landscapes with exotic shrubs (Lonicera spp. and Rosa multiflora); main predators in the urban area include Blue Jay, American Crow (Corvus brachyrhynchos), domestic cats, eastern gray squirrel (Sciurus carolinensis), eastern chipmunk (Tamias striatus), and raccoon (Procyon lotor) (Borgmann and Rodewald 2004).

Another study in Ohio found that nest success was correlated with nest height (higher nest were more successful) and nest height decreased with increasing urbanization (Reale and Blair 2005). Nest failure in most highly urbanized areas due to nest abandonment rather than depredation (Blair 2004).

Response to predators

Threat displays directed at predators, such as Blue Jays and snakes, consist primarily of visual mobbing behavior and chirp and chuck vocalizations (Shedd 1982, Gottfried et al. 1985). Chirps are more likely to be included in the repertoire of birds that ultimately attack a model predator; chucks are more likely to be included in the repertoire of individuals that do not (Gottfried et al. 1985). Robins often give one or two yeeps followed by several chuck calls, the number of yeeps and chucks may be correlated with threat level (ENV). Visual displays typical of mobbing consist of intention movements to approach or flee, such as wing-flicking, tail-wagging, and nervous hopping. Mobbing vocalizations are loud and high-pitched. Calls are generally ≥ 0.1 s in duration and of a narrow range of frequencies (Shedd 1982).

Known to exhibit a distinctive “wing-droop” aggressive stance when threatened (Sharp 1990). A mounted Screech Owl evoked 4 behaviors: silent approach, vocal approach, mobbing, and attacking (Shedd 1982). Mobbing and attacking appear beneficial only when robins are confined to territories, and the presence of young on territories further increases the amount of parental mobbing. Stage of the nesting cycle influences intensity of nest defense only weakly (Knight and Temple 1986b); in female robins responding to humans at nests, Alarm-Call rate, approach distance, and number of dives and strikes did not change significantly with time since initiation of incubation. In Kentucky, robins nesting near man-made structures (buildings, playgrounds etc.) gave fewer alarm calls than those far from such structures, indicating that they may habituate to human presence (ENV). Similarly in a study of flight initiation distances (FID) robins seem to be able to assess the threat posed by humans; FID was shortest when humans approached robins from a path without a direct gaze (not looking at them) than when humans approached them off a path and looking at them (Eason et al. 2006). In Seattle FIDs were shorter in urban areas as compared to rural areas and areas with light suburban development (Clucas and Marzluff 2012).

The time from when a robin alerts to an approaching predator and when it flies off varies with risk level; in simulated high risk situations (human approaching quickly) robins tend to fly off soon after alerting and give few alarm calls, whereas in lower risk situations (human walking) the time is greater, the distance the potential predator advances is greater, and robins give more calls and tailwag more often (ENV). Individuals gives high-pitched seet calls in response to aerial predators. Upon hearing these calls robins stop foraging and either stand alert, scan the sky, or squat and tilt head back and gaze towards the sky (skygazing; Vanderhoff and Eason 2009a). Both juveniles and adults respond to playbacks of seet calls; while juveniles tended to stand alert, adults engaged in significantly more skygazing behavior if calls were played at a higher rate (Vanderhoff and Eason 2009b).

Recommended Citation

Vanderhoff, N., P. Pyle, M. A. Patten, R. Sallabanks, and F. C. James (2016). American Robin (Turdus migratorius), version 2.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.462