Alagoas Antwren

Identification

The Alagoas antwren is 9.5 to 10.5 cm (3.7 to 4.1 in) long and weighs about 8 to 11.5 g (0.28 to 0.41 oz). It is a small bird with a short tail. Adult males are almost entirely gray, with lighter underparts than upperparts. Their throat feathers have black bases and gray tips. Adult females are mostly rufous-brown with darker wing coverts and paler cheeks and throat. Their iris is brown, their bill brownish gray, and their legs and feet leaden gray.

Taxonomy

The Alagoas antwren was originally described as a subspecies of the unicolored antwren (M. unicolor) but since the late twentieth century has been recognized as a full species. The two form a superspecies. The Alagoas antwren, the unicolored antwren (M. unicolor), the Yungas antwren (M. grisea), and the plain-winged antwren (M. behni) appear to form a monophyletic group with similar vocalizations and habitat requirements.<p>The Alagoas antwren's specific epithet honors David Snow, a British ornithologist "who was a pioneer in life history studies of Neotropical birds".

Scientific name

Myrmotherula snowi

Authority

Teixeira & Gonzaga, 1985

Order

Passeriformes

Family

Thamnophilidae

Genus

Myrmotherula

Range and habitat

The Alagoas antwren was first discovered in 1979, near Murici in the eastern Brazilian state of Alagoas, and for many years was known only from that area. In the early 21st century it was discovered at several sites in Pernambuco, about 500 km (310 mi) further north. However, by about 2020 it could again be found only at Murici. It inhabits isolated fragments of semi-humid lowland evergreen forest and is known only from the narrow elevational range of 430 to 790 m (1,400 to 2,600 ft). "No doubt the distribution was much more widespread and continuous, before most forests in this region were cleared".

Migration

Resident species

Behavior

The Alagoas antwren is a year-round resident throughout its range.<p>The Alagoas antwren's diet has not been detailed but is known to include insects. It usually forages in pairs and as part of a mixed-species feeding flock. It actively searches foliage both live and dead in the forest understory, typically between 5 and 8 m (20 and 30 ft) above the ground though at times almost to the ground. Eight years of monitoring the Murici site noted a few instances of pairs accompanying mixed-species feeding flocks but noted that other species typical of such flocks were seldom seen.<p>Prior to 2021 the Alagoas antwren's breeding biology was essentially unknown. The researchers who determined that it was a species collected a female with an egg in its oviduct in February and noted juveniles with their probable parents in May. A 2021 paper described the discovery of four nests. All were a deep cup made of fungal rhizomorphs with dried leaf fragments on the outside. They were suspended in branch forks between 1.1 and 1.6 m (3.6 and 5.2 ft) above the ground in different species of plant. The first was found in November and contained two eggs. The researchers monitored the nest for three days before it was apparently predated. During that time both parents incubated the clutch. The second nest was found in March with two damaged eggs and the third and fourth were empty in March. The researchers also mist netted juveniles between December and late April. They hypothesized that nest building began in September, egg laying in October/November, hatching in November/December, and fledging in December/January.<p>The Alagoas antwren's song is an "irregular series of very high, sharp, drawn-out, well-separated 'seeup' notes, each 'seeup' descending". Its calls include "a single-syllable kleek pair-contact call" and "a three-syllable (sometimes two-syllable), slightly descending vocalization, nyiih-nyeeh-nyaah" that appears to be an alarm call.

Conservation

Population trend

declining