Loess and Bee-eaters IV: Distribution of the rainbowbird (Merops ornatus Latham 1801) in Australia

The first three papers in the Loess and Bee-eaters series sought to establish links between the nesting of bee-eater birds (family Meropidae) and the occurrence of loess deposits. For the European bee-eater there is a close and fairly obvious relationship; for the Carmine bee-eater nesting in the 15 N band of Africa more assumptions and adjustments have to be made, and for the Blue-cheeked bee-eater nesting in the Indus region the relationship is becoming vague and more speculative. The trend continues with the Australian bee-eater- the rainbowbird (Merops ornatus). We lack precise maps of loess distribution in Australia and there is an equal lack of detailed and accurate maps of the distribution of rainbowbird nesting. Loess in Australia is elusive; the maps of Kriger and Scheidig show little detail and are essentially contradictory. If the deterministic theory of loess deposit formation were applied, it would suggest that loess should be found in the region where Pleistocene cold-phase mountain glaciers occurred. In the last glacial phase there was very little glacial occurrence in Australia; probably a limited region near Mount Kosciuszko. This places some glacial activity in the extreme southeast of the country. This agrees, more or less, with the data on the Kriger map. Fry has mapped the breeding zones of the rainbowbird and they are concentrated in the southeast and southwest. The maps are not precise but there does seem to be indications of co-existence of bee-eater nests and loessic regions. This is not the clearcut relationship which has been observed with the European bee-eater but it is suggestive. The ill-defined loess/dust regions and the poorly demarcated nesting zones of the rainbowbird do seem to be coincident. Better mapping is urgently required for loess in Australia, and nesting zones of M. ornatus. It may be that dust rather than loess is the ground material to be observed in Australia. There are still problems of integrating the dust and loess concepts, but mapping of dust deposits does produce some coincidence with rainbowbird nesting. The region of Vertisol occurrence appears to be a barrier to the spread of rainbowbird nesting.