[order] Passeriformes | [family] Icteridae | [latin] Dolichonyx oryzivorus | [UK] Bobolink | [FR] Goglu des pres | [DE] Bobolink | [ES] Soldadito Arrocero | [IT] Bobolink | [NL] Bobolink
Subspecies
| Genus | Species | subspecies | Breeding Range | Breeding Range 2 | Non Breeding Range |
| Coereba | oryzivorus | ||||
| Dolichonyx | oryzivorus | ||||
| Dolichonyx | oryzivorus | NA | n, c | c SA |
Physical charateristics
Bobolink is a plump medium-sized bird, with a relatively short tail showing pointed tips on rectrices, and with a prominent conical bill. This species is related to blackbirds and orioles. It is the only American species with black underparts and white patches on back. Male in breeding plumage is black with creamy-buff nape and conspicuous white scapulars and rump patch, from back to uppertail coverts. Wings are pointed, and tail feathers have spiked tips. We can see a buff stripping on back and buff edges on tertials.
Face is entirely black. Black bill is short and conical. Eyes are brown. Legs and feet are dark flesh. It has a long nail on the hind-toe.
During spring migration, male shows pale edging on black plumage.
Non breeding male has yellow-buff underparts with black streaks on flanks, back and undertail coverts. Tail and wings are brownish. On the head, black crown is separated by a yellowish line, and a fine black line extends behind the eye. Bill is pale.
Female resembles non breeding male, with duller plumage. She is browner on the head, with whitish line in centre of crown and above the eye.
Juvenile resembles female, but yellower.
Adult Bobolinks have two complete moults per year, the first in late summer-early autumn, and the second in late winter-early spring. Male and female show brighter buff colour on head and body when they are in fresh plumage. When in worn plumage, they are whitish on the sides of face and throat.
Face is entirely black. Black bill is short and conical. Eyes are brown. Legs and feet are dark flesh. It has a long nail on the hind-toe.
During spring migration, male shows pale edging on black plumage.
Non breeding male has yellow-buff underparts with black streaks on flanks, back and undertail coverts. Tail and wings are brownish. On the head, black crown is separated by a yellowish line, and a fine black line extends behind the eye. Bill is pale.
Female resembles non breeding male, with duller plumage. She is browner on the head, with whitish line in centre of crown and above the eye.
Juvenile resembles female, but yellower.
Adult Bobolinks have two complete moults per year, the first in late summer-early autumn, and the second in late winter-early spring. Male and female show brighter buff colour on head and body when they are in fresh plumage. When in worn plumage, they are whitish on the sides of face and throat.
Listen to the sound of Bobolink
[audio:http://www.aviflevoland.nl/sounddb/B/Bobolink.mp3]
Copyright remark: Most sounds derived from xeno-canto
| wingspan min.: | 27 | cm | wingspan max.: | 29 | cm |
| size min.: | 15 | cm | size max.: | 21 | cm |
| incubation min.: | 10 | days | incubation max.: | 13 | days |
| fledging min.: | 10 | days | fledging max.: | 14 | days |
| broods: | 1 | eggs min.: | 3 | ||
| eggs max.: | 7 |
Range
Bobolink breeds from southern Canada and northern United States, and southwards to Colorado, Indiana and northern New Jersey.
It winters in central and southern South America.
This species may be a very rare vagrant to Western Europe.
It winters in central and southern South America.
This species may be a very rare vagrant to Western Europe.
Habitat
Bobolink breeds in open and semi-open grassy areas. During migration and in winter, it can be found in freshwater marshes, grasslands and rice fields.
Reproduction
Bobolink nests in hayfields and meadows in spring, from May to early July. Nest is on the ground. It is a well-hidden open cup in dense vegetation, in a shallow depression at the base of a clump of grass. Exterior wall of nest is made with coarse grasses and weed stems, and lined with finer grasses. It may have a canopy of dead grass hanging over the top. Nest is built by female. The species may nests in loose colonies.
Female lays 3 to 7 bluish-grey to pale reddish-brown eggs, heavily spotted with dark. Incubation lasts about 10 to 13 days, by female. Male helps brood and feeds the young of its primary mate. Altricial chicks fledge at about 10 to 14 days after hatching. They fly at about 16 days. Nesting behaviour in Bobolink is particular. Sometimes, more than two adults are feeding the young at a single nest. ?Helper? can be a male or a female, and may be offspring from the previous year of one or both of the other adults. They also may be adults which lost their brood, and they need to feed young.
This species produces only one clutch per year.
Female lays 3 to 7 bluish-grey to pale reddish-brown eggs, heavily spotted with dark. Incubation lasts about 10 to 13 days, by female. Male helps brood and feeds the young of its primary mate. Altricial chicks fledge at about 10 to 14 days after hatching. They fly at about 16 days. Nesting behaviour in Bobolink is particular. Sometimes, more than two adults are feeding the young at a single nest. ?Helper? can be a male or a female, and may be offspring from the previous year of one or both of the other adults. They also may be adults which lost their brood, and they need to feed young.
This species produces only one clutch per year.
Feeding habits
This bird feeds on insects which are agricultural pests, and also on seeds from weeds. They forage while walking on the ground. Bobolink feeds in large flocks in both grasslands and agricultural fields, in the centre of South America, on their wintering areas. They mainly feed on rice crops during migration to the South. But in the North, they are insectivorous. Bobolink is also named ?Butter Bird?, because it is known to gorge itself in South Carolina and Georgia. Then, it becomes so fat that this species is hunted as game birds. It is also called ?Rice Bird? or ?Reed Bird?. But Bobolink is now protected.
Conservation
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Migration
The Bobolink breeds in old field habitats throughout North America. After breeding they congregate in marshes and other food rich and safe habitats to molt before a long migration. In fact is it among the longest migrations of New World passerines. Bobolinks appear to largely fly over water from the United States to northern South America. From there they proceed southward to winter in north-central Argentina, parts of Paraguay and Brazil. There they move about in monospecific flocks and inhabit moist grassland or larger marshes. Their primary food appears to be seeds during the non-breeding season. Flock sizes tend to be under 400 birds, although historically in northern Argentina flocks up to five thousands were known. Similarly in Argentina, their wintering distribution is now more restricted than it was historically. It does seem that Bobolinks in South America are nomadic, and in Argentina their presence is correlated with wet El Nino years, or other years of river flooding in the east of the country. In dry years it is assumed that Bobolinks winter farther to the north, being less common then in Argentina. Before migration northwards Bobolinks perform a complete molt, being the only passerine in the New World that has two complete molts a year. This is certainly an adaptation to the long distances it travels, particularly over water.
Distribution map
Literature
Title FACTORS AFFECTING HOW MALE AND FEMALE BOBOLINKS APPORTION PARENTAL INVESTMENTS
Author(s): JAMES F. WITTENBERGER
Abstract: Male and female Bobolinks (Dolichonyx oryzivorus) ..[more]..
Source: Condor 84~22-39, 1982
Title MULTIPLE PATERNITY IN A TERRITORIAL PASSERINE: THE BOBOLINK
Author(s): THOMAS A. GAVIN, ERIC K. BOLLINGER
Abstract: Electrophoretic and behavioral evidence corroborat..[more]..
Source: The Auk 102: 550-555
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