White-throated Magpie-Jay Calocitta formosa Scientific name definitions

One of the better-studied New World jays, the white-throated magpie-jay is a large blue, black and white bird that sports jaunty black plume. It occurs primarily in tropical dry forest, and tracks this habitat through its southern limit in Guanacaste, Costa Rica, turning it over to its close relative, the black-throated magpie-jay, around Jalisco, Mexico. During the dry season, white-throated magpie-jays subsist in large part on fruits, especially those of ant-acacias. After insect activity is stimulated by rains, they focus on insects, especially the larvae of large lepidoperans.

White-throated magpie-jays are highly social and breed cooperatively. Unusually among birds, the female offspring stay in the group and help their parents raise future broods, while male offspring disperse. Therefore, groups generally consist of a dominant female, her lone social mate, and a number of retained female offspring who feed the dominant female, nestlings, and fledglings. However, dispersing males (floaters) have carte blanche to enter territories and accompany groups while foraging. Floaters may visit multiple groups in a day, and group males show little aggression to them unless the dominant female is fertile.

Such a dynamic social scene lays the groundwork for a complex mating system. Dominant females are fairly faithful to their mates, but not entirely, with paternity going to both visiting floaters and to neighboring group males. Occasionally, a helper will start a nest of her own; she is not prevented from doing so, but the group will not help her unless the nest of the dominant female fails. In addition, helpers may act as brood parasites on the nests of their own mothers, laying eggs for the group to raise. Both sexes, therefore, compete for mating opportunities; males for a chance to pair with the dominant female, and females for the dominant position in the group.

Such reproductive skew within groups seems to have lead to the evolution of one of the more astonishing vocal systems in the bird world. Male magpie-jays can individually produce upwards of 60 vocalizations (probably many more), but they do so in an unusual context. When a magpie-jay of either sex encounters a low-threat predator or even an innocuous species such as a dove or guan, they may fly slowly and directly at the threat, calling loudly. In this context males may produce a wide range of chirps, whoops, pops, yells and clicks. One possible explanation is that because male magpie-jays do not defend any resources needed by females, their best opportunity to be noticed by females is during predator encounters, when groups must pay attention to conspecific alarm calls.

43–56 cm; 205–213 g. Long-tailed jay with slightly recurved erectile forecrown crest of long black feathers (reaching 70 mm on some individuals) with whitish or bluish margins at base or, sometimes, reaching middle and almost all of feather. Male nominate race has crown and nape variable, black, or black with some feathers barred white and blue, or black just behind crest and sky-blue elsewhere; side of head, side of neck and throat to breast white (on some slightly washed bluish), sometimes white above eye forming supercilium (which begins at base of upper mandible); some dark feathers, sometimes bluish, around eye, and a blue-black malar stripe (often mottled) not reaching bill; sepia or blackish area bordering rear ear-coverts and extending as narrow U-shaped band across lower breast and frequently over base of hindneck; upper­parts sky-blue, heavily tinged grey, rump slightly tinged green; upperwing bright sky-blue, inner margins of primaries brownish; long tail graduated, two central pairs of feathers entirely bright blue, other feathers blue only on basal half and whitish elsewhere; underparts below breast­band white, somewhat tinged grey; underwing-coverts white, contrasting somewhat with grey underside of flight-feathers; iris dark brown; bill and legs black. Female is like male, but has shorter tail, more extensive blackish on ear-coverts, narrower breastband, and upper­parts slightly duller. Juvenile is similar to female, but central tail even less elongated, crown whiter, crest shorter and with feathers tipped blue and/or white, bill and legs greyer, upper­parts duller greyish-blue, breastband narrower; much as adult after first moult, except that tail shorter. Race azurae is slightly larger than nominate, with crown and nape also variable but blue deeper, normally less black on face, female and juvenile more greyish on upperparts and wings, male brighter, tending to cobalt-blue, on upperparts and wings, no sepia on hindneck; <em>pompatus</em> is smallest race, similar to previous, but upperparts and wings sky-blue with heavy grey tinge (as in nominate), side of head, throat and breast slightly washed blue.

Editor's Note: This article requires further editing work to merge existing content into the appropriate Subspecies sections. Please bear with us while this update takes place.

• Black-throated x White-throated Magpie-Jay (hybrid) Calocitta colliei x formosa

Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Arid to semi-humid woodland, from lowlands to 800 m, reaching 1250 m in some localities. Inhabits areas of thorn-forest, deciduous forest and gallery forest, frequently visiting forest edges and bushy open country; regularly seen at borders of cultivation (coffee plantations). In C Mexico recorded, rarely, in columnar cacti forest. In most of range associated with more arid areas, but on Pacific side of S Chiapas and N Guatemala found in areas of heavier rainfall. In Central America, found in more arid habitats than those occupied by Cyanocorax morio. Also frequents larger clumps of trees and broken forest, especially along watercourses. In Costa Rica seems to prefer disturbed areas, being common in woodland and brushy cattle pasture; in Santa Rosa National Park, occurs in both woodland and pastures. In El Salvador considered an open-habitat generalist.

Reported items in diet are large invertebrates, small lizards, frogs, eggs and nestlings of small birds, also seeds, fruits , berries and grain (maize); nectar from large Balsa blossoms also consumed. In study in Costa Rica, this species spent more time foraging in woodland during wet season, when caterpillars (Lepidoptera) eaten in larger proportion than in dry season; during dry season consumed mostly fruits, particularly from acacia (Acacia) but also from Curatella americana, Ficus, Spondias mombin, Byrsonima crassifolia and Muntingia calabura; insects, including Orthoptera, and arachnids recorded in diet through the year. Fledglings in Costa Rica differed from adults in diet, taking relatively fewer arthropods and more fruits; young approach adult levels of foraging proficiency within one year. Forages in groups at all forest levels, including ground, where it moves in bouncing hops; investigates foliage, hanging tangles, leaf bases of bananas, and ground litter.

Quite rich repertoire, some vocalizations suggesting a large parrot (Psittacidae). Twelve vocalizations identified in one study, but variations of these quite common. Harsh downward-inflected "jeer!", and guttural "raah" or "reeah" when scolding. Other harsh notes include frog-like snore sound, squawking "schrrrr", and rolling or trilling downslurred "prrrreeeeeo". Melodic notes, sometimes described as liquid sounds, include clear inflected whistle, short snoring "clooo", "poop!", "weep-weep-weep", and piping note; also described are "kreeup", upslurred "reek", and loud "pee-ah", this last given by nesting female. Two vocalizations (termed "pump-handle" and "squeaky-gate" calls) sometimes combined in single vocalization, which is similar to those given by Cyanocitta stelleri. Subsong (sotto voce) recorded.

Eggs recorded in Guatemala late Dec and early Jan in W and Jun and Jul on Caribbean slope, and mid-Apr in El Salvador; eggs in Feb–Jul and nest activity peaking in Mar–May in Costa Rica. Breeding system flexible, varying from single breeding pair within a given group range to multiple breeding pairs within a given group range, with partial range-sharing among related females; additionally, and unlike other American jays with helpers, has a male-biased natal dispersal, the groups consisting primarily of related matrilocal females which remain on natal territory as helpers, males dispersing from natal territory by 4–23 months of age to exist as floaters or join another group. Group-members assist with nest defence and the feeding of breeding female and her offspring; quantitative data from Costa Rica suggest higher proportion of food given by helpers when compared with other co-operatively breeding New World jays. In Costa Rica, territory size (10–31 ha) of 14 monitored groups (of 2–10 individuals) did not vary for three years, larger groups possessing larger territories containing more bull-horn (Acacia), a critical food resource during dry season; quantitative data suggests that group size and Acacia density are directly related to group breeding success. Detailed study in Santa Rosa National Park (Costa Rica) concluded that helpers increased breeding success by hastening onset of first laying, reducing predation on eggs and chicks, and decreasing hatching failure (presence of helpers did not affect incidence of clutch desertion or chick starvation). Bulky nest 12·7 cm in diameter, constructed by both sexes, made of large twigs, lined with rootlets, placed 6–30 m up in tree; in Guatemala (Colomba) one was placed in top of clump of tall bamboos growing beside stream and three others in shade tree of coffee plantation; in Costa Rica nests located in isolated trees in middle of pasture or near human dwellings, and suggested that sites chosen in order to avoid nest predation by monkeys. Clutch 2–6 eggs; incubation period unrecorded; nestling period 23 days.

Not globally threatened. Common resident in most of its geographical range. Common to fairly common in Mexico; common in Costa Rica .