Behavior

Tropical Kingbirds usually perch conspicuously, sallying in pursuit of aerial arthropod prey (described in Fitzpatrick 1980), which is the most common foraging maneuver utilized (Fitzpatrick 1980, Rosenberg 1990, Cintra 1997, Gabriel and Pizo 2005, Jahn et al. 2010a). This foraging technique accounted for 94% of 425 foraging observations made in Peru (Fitzpatrick 1980). Kingbirds also may take prey from the ground, foliage or water, taking large prey items back to the perch, where it may beat them against the perch before consuming them (Fitzpatrick 2004; AEJ personal observations). Sally distances vary from 2 m to >30 m; longer sallies sometimes involve acrobatic chasing of the flying prey (Skutch 1954, 1960, Smith 1966, Fitzpatrick 1981). Multiple prey items may be taken in a single sally before the kingbird returns to a perch (Skutch 1954, 1960, Fitzpatrick 1981). Forages primarily during the day, but has been seen after dark taking flying insects near lights (Fitzpatrick et al. 2004).

Tropical Kingbirds sometimes hover and pluck fruit from vegetation (McDiarmid et al. 1977, Stiles and Skutch 1989). For example, when consuming Stemmadenia donnell-smithii (Apocynaceae), kingbirds will hover below fruit and swallow the pulp and seeds (McDiarmid et al. 1977).

Kingbird populations are migratory in extreme northern (e.g., Arizona, USA) and extreme southern (e.g., Argentina) portions of their extensive range. In South America, two subspecies (satrapa and despotes) appear to be permanent residents in northern Amazonia (Traylor 1979a, Chesser 1995), whereas kingbirds of the nominate subspecies are permanently resident or partially migratory in Amazonia north of ca 18°30' S (Chesser 1997, Jahn et al. 2010b). Research suggests that in these partially migratory populations, larger males are more likely to migrate than conspecifics (Jahn et al. 2010b). In southern Bolivia, Paraguay, Argentina, Uruguay and southern Brazil, the nominate subspecies occurs only during the austral summer, migrating north into tropical South America after breeding, within the range of the permanent resident populations (Chesser 1995).

Migratory routes remain unknown throughout most of the range because of the overlap during migration and winter of migratory populations with permanent resident populations. However, large flocks of austral migrants (the nominate subspecies) are seen May-September in northern Amazonia, with migrants overlapping with residents in northern South America March-October (Mobley 2004). Overwintering austral migrants occasionally observed as far north as Netherlands Antilles and Cuba; possible transients in Ecuador (i.e., numbers there increase in April-May; Mobley 2004).

In 2010, a light-level geolocator was deployed on one breeding individual of the nominate subspecies in the province of Buenos Aires, Argentina. This bird spent the austral winter principally in southeastern Colombia, approximately 4000 km from the breeding site (AEJ, unpublished data).

Non-migrant Tropical Kingbirds maintain territories all year, although migratory birds may be non-territorial during the nonbreeding season. Migratory kingbirds form flocks (ffrench 1973, Ridgely and Tudor 1994), which can consist of 10–30 birds and sometimes include White-throated Kingbirds (Tyrannus albogularis; Ridgely and Tudor 1994, PCS, personal observation).

Based on radio-telemetry research in eastern Bolivia, Jahn et al. (2010c) recorded a mean territory size of 43.0 ha (SD ± 22.6 ha) for males, and of 45.6 ha (± 45.5 ha) for females. Tropical Kingbirds held smaller territories in the nonbreeding season than in the breeding season, although differences between seasons were not significant (Jahn et al. 2010c).

One pair of mated kingbirds in northern Argentina nested in the same tree during four consecutive seasons (Jahn et al. 2009), suggesting that at least some kingbirds are faithful to their territories between years.

Tropical Kingbirds are at least socially monogamous (Skutch 1954, 1960), although no studies have yet been done to document extra-pair copulation. One pair of banded kingbirds in northern Argentina remained together during the breeding season, over four consecutive years (Jahn et al. 2009).

The sociality of Tropical Kingbirds varies according to time of year and whether individuals are migratory (see Territoriality). Males indicate potential nest sites to females by squatting and vocalizing softly (Skutch 1954, Smith 1966), which may be more important for pair-bond formation or maintenance than for nest-site selection (Smith 1966). In courtship, perched birds call and flap wings (ffrench 1973), make short flights from their perch, and vocalize (Skutch 1954, Smith 1966). Permanent residents may maintain year-round pair bonds (Skutch 1954).

Tropical Kingbirds are very aggressive towards potential nest predators, and even apparently nonthreatening birds. In Central America, a kingbird was aggressive towards a Social Flycatcher (Myiozetetes similis) but not towards a pair of Bananaquits (Coereba flaveola; Skutch 1954). Nesting kingbirds also displace Groove-billed Anis (Crotophaga sulcirostris) and Golden-fronted Woodpeckers (Melanerpes aurifrons; Skutch 1954). Tropical Kingbirds have also been observed displacing other Tropical Kingbirds, a Yellow-green Vireo (Vireo flavoviridis), and a Yellow Warbler (Setophaga petechia; McDiarmid et al. 1977).

Adults depredated by Aplomado Falcons (Falco femoralis) in Mexico (Hector 1985) and Bat Falcon (Falco rufigularis) in Bolivia (Q. Vidoz, personal communication). Nests depredated by Swallow-tailed Kites (Elanoides forficatus; Skutch 1954) and Black-mandibled Toucans (Ramphastos ambiguus swainsonii; Skutch 1954).