Pectoral sparrow
The pectoral sparrow is a small species of bird in the family Passerellidae, first described in 1779. It is found in Bolivia, Brazil, Colombia, French Guiana, Guyana, Peru, Suriname, and Venezuela. Its natural habitat is subtropical or tropical moist lowland forests.
Taxonomy
The pectoral sparrow was described in 1779 by French polymath Georges-Louis Leclerc, Comte de Buffon in his Histoire Naturelle des Oiseaux under the French name "L'Oiseau Silencieux". It was also illustrated in a hand-colored plate that was produced to accompany Buffon's book. Buffon did not use binomial names but in 1783 the French naturalist Johann Hermann coined the name Tanagra taciturna. The specific epithet taciturnus is the Latin word for "silent" or "quiet". The species is now placed in the genus Arremon that was erected by the French ornithologist Louis Pierre Vieillot in 1816 with the pectoral sparrow as the type species.Two subspecies are recognized:
The yellow-mandibled sparrow was formerly considered as a subspecies.
Description
The pectoral sparrow is sexually dimorphic, and, as the name implies, sparrow-sized, at in length and in weight. Its upperparts are pale green, becoming yellow near the bend of the wing. The head is black, with white on its throat and as stripes on its crown. Its underparts are white or creamy, with males also having a broad black band going across their breast. The beak is also black, roughly long for both males and females. Tails are and wings are for males and females respectively. Its iris is brown, and its tarsi and toes are pinkish gray.Male and female plumage is distinctly different, with females having dull olive upperparts instead of bright yellow, a grayish pectoral band, and greyer, darker underparts.
The pectoral sparrow is fairly unique in its habitat, as a result, it is usually the only small forest sparrow with a striped head in its range. They can be differentiated from the orange-billed sparrow, which they border distribution with in eastern Columbia, by the namesake orange bill, as well its inverted throat colors.
Distribution and habitat
Pectoral sparrows can be found everywhere in the Amazon Basin east of the Andes except for the western parts between the Negro and Purus rivers. Besides the Amazon jungle, it is found in eastern and north-eastern Brazil. They occupy altitudes up to in southern Venezuela, in southeastern Peru, and in Bolivia. They do not migrate. They occupy the lowland undergrowths of humid evergreen forests or secondary forests, and infrequently in lighter woodlands or coffee plantations, often when near humid wooded ravines.Behavior
The pectoral sparrow is socially monogamous, however much of its breeding behavior is not well studied.Breeding
Nests are spherical, bulky, and roofed, with an entrance on the side, around in length, width and height respectively, and in weight. They consists of 2 layers the outer layer, which is composed of dried bamboo, leaves, roots, and twigs, totaling around in weight. The inner layer is much lighter, at, and is composed of leaves and pale brown rootlets. Eggs are on average in length and width and weighing. All nests studied had 2 eggs per clutch. Egg markings are highly variable; some were completely white, others speckled with varying amounts of brown spots.Incubation is thought to take 1517 days, with the female observed acting as the sole incubator. Incubation was done in periods, averaging 71 minutes. Females averaged 7.4 trips outside the nests per day, each averaging 46 minutes, however trips increased in frequency as the eggs neared hatching, going from 61% of daylight spent incubating during days 410 to only 55% during days 11-15. Fecal sacs were solely removed by males.
The phenology of the pectoral sparrow is unknown, however a 2011 study by Valdez-Juarez et al. found recently laid eggs across the entire period of the study, from late August to early December. Additionally, out of the 15 nests studied, only 2 eventually hatched, the remaining having been abandoned or predated upon.