(Website editor: I acquired these Proceedings from a book stall at the Parrot Society show at Sandown earlier this month (April 2000). They are interesting in providing a very concise exposition of the level of knowledge on the Blue Macaws at the time.)
Glaucous Macaw (Anodorhynchus glaucus)
Range: The Glaucous Macaw has not been recorded in the wild since the l9th century, and it is probably now safe to assume that the species is extinct. It was recorded from only a small area in southeastern South America, evidently centered on the lower Paraguay and Parana Rivers, from whence come most of the few specimens with data (none of it precise). It is known to have occurred in southeastern Paraguay, northeastern Argentina (at least in Corrientes, from which there are several extant specimens), and Rio Grande do Sul in extreme southeastern Brazil (no specimens, but Belton (ms.) notes that a traveler in the 1820's wrote convincingly of seeing this species). A. glaucus probably also once occurred in northern Uruguay (Artigas), but again there are no extant specimens (Cuello and Gerzenstein 1962).
Habitat: The Glaucous Macaw evidently occurred in the sub-tropical forests found along the region's larger rivers. It probably also occurred away from them, the concentration of reports from riverbanks simply being due to these being where travelers could see them, there being little or no access into the interior.
Status: The Glaucous Macaw seemingly used to be not uncommon within its relatively limited range. Specimens were taken up to at least 1860 (in Corrientes, in USNM). The last known specimen to have been seen alive was one, thought to be from Brazil, exhibited in the Buenos Aire's Zoological Gardens in 1936 (Orfila 1936); a photo of this bird cannot be definitely identified, but is certainly either this species or A. leari. If it was in fact the latter, then the last known live specimen was another captive seen at the Jardin d'Acclimation in Paris from 1895 to 1905 by Jean Delacour (Sick and Teixeras 1980).
I conducted surveys through much of the Glaucous Macaw's range in Paraguay in July-Aug. 1977, and could find no evidence that the species still exists. Not only did I myself not see it, but local residents did not know it. Many were familiar with Ara chloroptera, though that macaw was far from common locally. The active bird dealers in Asuncion told me that they had never been able to obtain a specimen of this species; some had tried to, being fully aware how rare (and valuable) such a specimen would be.
Exactly what happened to the Glaucous Macaw is a mystery. Early observers, among them Azara (1805) found them quite common along the Parana River in the late l8th century; here he saw "a number of pairs" and noted that "it nested not only in hollows of trunks, but also, and with greater frequency, in ones made in the vertical banks of the Parana and Uruguay Rivers." It would appear that neither deforestation nor any other form of habitat disturbance can have caused its decline, for extensive forest remains over much of the species former range, especially in Paraguay. Furthermore only in the last few decades, long after the Glaucous Macaw had declined, did any serious habitat disturbance begin to take place.
Hunting seems unlikely to have been the major cause of such a rapid decline, though the species could have been unusually vulnerable, especially if in fact it was found mostly along the larger rivers. Several much favored gamebirds, among them the curassow Crax fasciolata, however, are still found in good numbers in the very same forests. Conceivably, a natural catastrophe played a role (perhaps some pathogenic factor, or an unusually cold spell, which greatly reduced available food), or possibly the species simply declined on its own. We are unlikely ever to know what happened, for much as with the Carolina Parakeet (Conuropsis carolinensis), the species slipped away before anyone realized it was going.
Summary: Almost certainly extinct, perhaps the first South American bird to become so since western colonization. The reasons for its decline remain obscure, as discussed above. Conceivably a small population yet persists in some small pocket of unexplored forest, but I consider it decidedly unlikely.
" Naturam expellas furca, tamen usque recurret "
( If you drive out nature with a pitchfork, she will soon find a way back)
Horace (65-8 BC)