PURPOSE Choroidal vessels compensate for changes in systemic blood pressure (BP) so that choroidal blood flow (ChBF) remains stable over a BP range of approximately 40 mm Hg above and below basal. Because of the presumed importance of ChBF regulation for maintenance of retinal health, we investigated if ChBF compensation for BP fluctuation in pigeons fails with age. METHODS Transcleral laser ...

Spontaneous infection with the virus of psittacosis is known to be widespread among birds of the psittacine family and also to occur in members of other orders of the class, Ayes (1). Coles (2) in 1940 described an epizootic of psittacosis among domestic pigeons (Columba livia vat. domestica) in South Africa and this disease was later encountered among pigeons in many parts of the United States...

Previous research suggests that when a fixed interval is interrupted (known as the gap procedure), pigeons tend to reset memory and start timing from 0 after the gap. However, because the ambient conditions of the gap typically have been the same as during the intertrial interval (ITI), ambiguity may have resulted. In the present experiment, the authors found that when ambient conditions during...

Three avian species, a seed-caching corvid (Clark's nutcrackers; Nucifraga columbiana), a non-seed-caching corvid (jackdaws; Corvus monedula), and a non-seed-caching columbid (pigeons; Columba livia), were tested for ability to learn to find a goal halfway between 2 landmarks when distance between the landmarks varied during training. All 3 species learned, but jackdaws took much longer than ei...

In a series of four experiments, we explored whether pigeons complete partially occluded moving shapes. Four pigeons were trained to discriminate between a complete moving shape and an incomplete moving shape in a two-alternative forced-choice task. In testing, the birds were presented with a partially occluded moving shape. In experiment 1, none of the pigeons appeared to complete the testing ...

Pigeons are known to be able to categorize a wide variety of visual stimulus classes. However, it remains unclear which are the characteristics of the perceptually relevant features employed to reach such good performance. Here, we investigate the relative contributions of texture and shape information to categorization decisions about complex natural classes. We trained three groups of pigeons...

The ability of pigeons to find their way home from unfamiliar sites located up to hundreds of kilometers away is well known, but the mechanisms underlying this ability remain controversial. One proposed mechanism is based on the suggestion that pigeons are equipped with magnetoreceptors that can enable the detection of either the earth's magnetic field and/or magnetic field anomalies in the loc...

Four pigeons were trained in a successive same/different procedure involving the alternation of two stimuli per trial. Using a go/no-go procedure, two different or two identical color photographs were alternated, with a brief, dark, inter-stimulus interval, on a computer screen for 20s. Pigeons learned to discriminate between same (S+) and different (D-) sequences with moderate to large contras...

Pigeons are considered to play key ecological roles in frugivory and seed dispersal. They have colonised numerous oceanic islands diversified into several species sympatry. How these coexist similar niches is poorly understood although dietary separation among the mechanisms suggested avoid trophic overlap. We investigated ecology of two endemic Columba co-occurring laurel forest thermoscleroph...

The olfactory navigation hypothesis proposed to explain homing pigeon predicts that birds learn the association of wind directions and wind-borne odours at home, once displaced, determine home direction on basis local environmental release site. This was two kinds empirical observations: (i) pigeons develop navigational abilities only if exposed winds loft, (ii) anosmic displaced unfamiliar sit...