Anatomical Specializations for Nocturnality in a Critically Endangered Parrot, the Kakapo (Strigops habroptilus)

The shift from a diurnal to nocturnal lifestyle in vertebrates is generally associated with either enhanced visual sensitivity or a decreased reliance on vision. Within birds, most studies have focused on differences in the visual system across all birds with respect to nocturnality-diurnality. The critically endangered Kakapo (Strigops habroptilus), a parrot endemic to New Zealand, is an example of a species that has evolved a nocturnal lifestyle in an otherwise diurnal lineage, but nothing is known about its' visual system. Here, we provide a detailed morphological analysis of the orbits, brain, eye, and retina of the Kakapo and comparisons with other birds. Morphometric analyses revealed that the Kakapo's orbits are significantly more convergent than other parrots, suggesting an increased binocular overlap in the visual field. The Kakapo exhibits an eye shape that is consistent with other nocturnal birds, including owls and nightjars, but is also within the range of the diurnal parrots. With respect to the brain, the Kakapo has a significantly smaller optic nerve and tectofugal visual pathway. Specifically, the optic tectum, nucleus rotundus and entopallium were significantly reduced in relative size compared to other parrots. There was no apparent reduction to the thalamofugal visual pathway. Finally, the retinal morphology of the Kakapo is similar to that of both diurnal and nocturnal birds, suggesting a retina that is specialised for a crepuscular niche. Overall, this suggests that the Kakapo has enhanced light sensitivity, poor visual acuity and a larger binocular field than other parrots. We conclude that the Kakapo possesses a visual system unlike that of either strictly nocturnal or diurnal birds and therefore does not adhere to the traditional view of the evolution of nocturnality in birds

The effect of colour on bait consumption of kea ( Nestor notabilis

The kea (Nestor notabilis), an endemic parrot, is at risk of primary poisoning during 1080 possum control operations. This project aimed at providing information on the effect of colour on bait attractiveness for kea to ultimately increase the safety of toxic bait. A feeding trial with captive kea investigated their colour preferences by offering cake dyed in six different colours simultaneously over six consecutive days. On average, the order of preference was yellow>red>brown>mid-blue>dark-blue>green; all birds encountered and consistently consumed less green bait than all the other colours throughout the trial. These results suggest that green is the most promising colour to deter captive kea from feeding in a multi-choice situation. However, due to kea's opportunistic feeding behaviour and inquisitive nature this might not be the case if green is the only option, suggesting that a stronger deterrent than colour may be necessary to deter free-ranging birds from consuming toxic bait

Primary poisoning risk for encapsulated sodium nitrite, a new tool for pest control

Acute toxicity of sodium nitrite (NaNO₂) was assessed in chickens (Gallus gallus domesticus) and domestic mallard ducks (Anas platyrhynchos domestica) by oral gavage and in free-feeding trials with chickens, domestic mallard ducks, pigeons (Columba livia f. domestica), budgerigars (Melopsittacus undulates) and wētā (Family: Rhaphidophoridae). Free-feeding trials involved the presentation of toxic paste and pellet baits containing encapsulated NaNO₂ developed for the control of common brushtail possums (Trichosurus vulpecula) and feral pigs (Sus scrofa). The oral gavage LD₅₀ value for NaNO₂ in solution was approximately 68.50 mg/kg (95% CI 55.00–80.00 mg/kg) for both chickens and ducks. In feeding trials, six out of 12 chickens consumed toxic paste bait and four of these birds consumed a lethal dose. When chickens consumed toxic paste bait, the LD₅₀ value was approximately 254.6 mg/kg (95% CI 249.1–260.2 mg/kg). Of the other three species of birds presented with toxic baits only one duck consumed a lethal dose of paste bait. There was no evidence of wētā feeding on toxic baits