Spix's Macaw - Distribution and Habitat

Distribution and Habitat

Spix's Macaw was most recently (1974-1987) known in the Río São Francisco valley, in northeastern Brazil, principally in the basins on the south side of the river in the State of Bahia. In 1974, ornithologist Helmut Sick, based on information from traders and trappers, extended the possible range of the Spix's Macaw to embrace the northeastern part of the state of Goias and the southern part of the state of Maranhao. Other ornithologists reporting the bird in various parts of the state of Piaui further extended the range to a vast area of the dry interior of northeast Brazil.

Study of the lone bird discovered at Melância creek in 1990 revealed substantive information about its habitat. It had been previously assumed that the Spix's Macaw had a vast range in the interior of Brazil embracing several different habitat types, including buriti palm swamps, cerrado, and dry Caatinga. But the evidence collected in Melância Creek indicated that the Spix's Macaw was a specially adapted inhabitant of the disappearing woodland galleries. Ornithologist Tony Silva mentions that "where craibeiras have been felled, as in the Pernambuco side of the São Francisco River, the species has disappeared". Previous observations of the birds elsewhere were attributed to birds migrating between possibly isolated areas of habitat, birds displaced from older habitats by deforestation, or birds expansively hunting for scarce nesting sites.

Other recent evidence has shown that anthropic changes that occurred on the northern shore of the São Francisco River, such as a broad scale conversion into agricultural lands and flooding following the construction of Sobradinho dam starting in 1974, have changed the flora structure and displaced the Spix’s Macaw away from that portion of its original range.

Much remains uncertain about the extent of the bird's original range, because most of its woodland habitat was cleared before naturalists observed either the birds or the Caraiba nesting sites. The historical range is now believed to have encompassed portions of the states of Bahia and Pernambuco in a 50 km (31 mi) wide corridor along a 150–200 kilometres (93–120 mi) stretch of the Rio São Francisco between Juazeiro (or possibly Remanso) and Abare.

The caatinga vegetation of northeastern Bahia (which hosts the Spix habitat) is stunted trees, thorny shrubs and cacti, prevailed by plants of the family Euphorbiaceae. This macaw lived in the hottest and driest part of the “Caatinga” within Caraiba, or Caribbean Trumpet Tree (Tabebuia caraiba) woodland galleries. The Caraibeira woodland galleries constitutes a microclimate within the Caatinga. The existing galleries are fringes of unique woodland extending a maximum of 18 metres (59 ft) to either side along a series of seasonal waterways at least 8 m wide in the Rio São Francisco drainage basin. All T. caraiba woodland was recorded in the middle and lower levels of the creek system where fine alluvial deposits were present. The character of the galleries is tall (8m) evenly spaced Caraibeira trees, ten per hundred meters, interspersed with low scrub and desert cacti. Large mature trees of this species (and apparently no other) provided the nesting hollows of the Spix Macaws, as well as shelter and their seedpods, food for the species.

Notable among the seasonal waterways are Riacho Melância watershed 30 km south of Curaçá, where the last known wild Spix's Macaw nest was located, adjacent Riacho Barre Grande, and Riacho Vargem to the north all in the State of Bahia south of Rio São Francisco. In 1990, these were all that remained of what was once believed to be a vast filigree of creekside Caraibeira woodland extending 50 km into the Caatinga on either side of the Rio São Francisco along a significant stretch of its middle reaches. There is also one confirmed site, since cleared, on the north shore of Rio São Francisco in Pernambuco. Caraiba grows very slowly; most of the trees are 200–300 years old, and there has not been any regenerative growth for the last 50 years.

In addition, 45% of the Caatinga dry forest in which the woodland galleries are embedded has been cleared for farms, ranches and plantations. Climate change resulting in desertification of significant parts of the Caatinga has permanently reduced the potential reclaimable habitat.