It is impossible to know the original population size and distribution of Anodorhynchus hyacinthinus, but it is known that it was an abundant species at the beginning of the century. Today it is threatened with extinction throughout its distribution area and the latest estimates report that some 3,000 macaws exist in the wild.
This work was conducted from January 1991 to March 1993 on 11 ranches covering an area of 250,000 ha (625,000 acres) in the Nhecolandia region of the Pantanal. Its main aims were 1) to locate and describe the nest sites of the Hyacinthine Macaw, 2) to study some aspects of its reproductive biology, 3) to determine its habitat requirements and 4) to seek management options for the conservation of the species.
Of the 94 nests identified, 95% were found in just one tree species, the " manduvi" (Sterculia striata), which has a soft core and is thus susceptible to the formation of hollows. Hyacinthine Macaws do not appear to select nest sites with standardised characteristics, such as the shape and size of hollows. However they showed a preference for fairly open vegetation areas or the margins of dense woodland and forest islands.
In the wild Hyacinthine Macaws produce asynchronously 1 to 3 eggs, 2 on average. The eggs were incubated by the female, which remained in the nest most of the time and was fed by the male. The incubation period varied from 28 to 30 days and the hatching rate for the period of the study was 90%. The young hatched weighing an average of 31.6 g and measuring 82.7 mm long. However they increased in size and gained weight rapidly. They stayed in the nest for approximately 107 days and after fledging continued to be fed by the parents. 40% of the eggs were predated, but the survival rate of the young varied between 75% and 83%. The reproductive success during the two years was 1.25 chicks per pair.
Hyacinthine macaws proved to be one of the most specialised birds in their feeding habits with their diet consisting mainly of nuts of two palm species - "bocaiuva" (Acrocomia totai) and acuri (Scheelea phalerata). For most of the year they fed on acuri nuts, which are highly nutritious and abundant with a density of 183.4 acuri trees/ha (73.5 per acre) in some areas producing fruit throughout the year.
The pairs of Hyacinthine Macaw were highly conspicuous, sedentary and exhibited a certain degree of fidelity to nesting sites. Non-reproductive individuals showed a high degree of socialisation and formed groups, both at foraging sites and in the roosting trees, the latter appearing to function as veritable " information exchange centres."
The availability of suitable hollows for the size of macaws is low and there is competition with other species for existing nest sites. This factor, together with the destruction of potential nests by deforestation and/or burning, may be preventing an increase of the population in the Pantanal area. For this reason some proposals concerning the management of nest sites and other options have been made to contribute to the conservation of the species in its natural habitat.
The research work of the Projeto Arara Azul/UNIDERP
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