Why Australia lacks ant-eating woodpeckers

Robin and the Honey Badger respond: “Migrating woodpeckers have proven to be capable of erratic flights of hundreds of kilometres. The gap between Australia and Timor at lowest sea level was only 80 kilometres. Therefore, woodpeckers would probably have reached Australia many times, but failed to colonise this continent partly because its ants, although abundant, are not productive enough. Australia has many genera of ants which support woodpeckers on other continents, but various lines of evidence suggest that these genera reproduce more slowly in Australia than elsewhere. Firstly, ant-eating mammals in Australia are considerably smaller, and consume fewer ants per unit area annually, than counterparts on other continents. Secondly, the few birds that do eat ants in Australia take them mainly as workers and soldiers, in contrast with the specialized ant-eating birds elsewhere which rely on ant brood. And thirdly, the carton nests made by ants in Australia are small relative to those produced by the same genera of ants on other continents. The ultimate reason for the poor productivity of ants in Australia and the consequent lack of ant-eating woodpeckers is a widespread poverty of nutrients across this ancient and extremely weathered continent.”