Inference by exclusion in the red‐tailed black cockatoo (Calyptorhynchus banksii)

Inference by exclusion is the ability to select a given option by excluding the others. When designed appropriately, tests of this ability can reveal choices that cannot be explained by associative processes. Over the past decade, exclusion reasoning has been explored in several non‐human taxonomic groups, including birds, mainly in Corvids and Parrots. To increase our understanding of the taxonomic distribution of exclusion reasoning and, therefore, its evolution, we investigated exclusion performances in red‐tailed black cockatoos (Calyptorhynchus banksii), an Australian relative of the Goffin cockatoo (Cacatua goffini), using a food‐finding task. Cockatoos were required to find a food item hidden in 1 of the 2 experimenter's hands. Following training sessions in which they reliably selected the closed baited hand they had just been shown open, each individual was tested on 4 different conditions. Critical to demonstrating exclusion reasoning was the condition in which they were shown the empty hand and then offered a choice of both closed hands. The performance of all birds was above chance on all experimental conditions but not on an olfactory and/or cuing control condition. The results suggest that the birds might be able to infer by exclusion, although an explanation based on rule learning cannot be excluded. This first experiment in red‐tailed black cockatoo highlights the potential of this species as a model to study avian cognition and paves the pathway for future investigations.     

Deep percolation during prolonged ponding of a swelling soil,and the effect of gypsum treatment

A sodic clay soil (a Vertisol) was instrumented from a 5 m deep pit to avoid the problems of preferential cracking around surface installations. Infiltration rates and changes in water content and vertical swelling at a number of depths in the soil profile were measured during prolonged ponding (139 and 160 days on separate plots). Essentially no deep percolation in one plot contrasted with a substantial amount (6.6 mm day^?1) in the second, gypsum-treated plot, with obvious consequences for changes in ground-water level. A method of calculating deep percolation is presented which takes into account the effects of swelling.