Mysterious Australian Night Parrots may not see in the dead of night

Australia's most elusive bird, the Night Parrot, may not be much better at seeing in the dark than other parrots active during the day

Date: June 9, 2020

Source: Flinders University

Australia's most elusive bird, the Night Parrot, may not be much better at seeing in the dark than other parrots active during the day.

An international study, co-led by Flinders University's Dr Vera Weisbecker, has revealed the critically endangered parrot's visual system is not as well-adapted to life in the dark as would be expected for a nocturnal bird, raising concerns it might be adversely impacted by fencing in the Australian outback.

"Night Parrots must be able to find their way at night -- to find food, avoid obstacles while flying, and escape predators," says Dr Weisbecker.

"We therefore expect their visual system to show adaptations for seeing in the dark, similar to other nocturnal birds -- New Zealand's Kakapo parrot and owls with enlarged eyes for example. However, we found that this wasn't the case."

Continued

Hummingbird vision wired to avoid high-speed collisions

Date: July 18, 2016

Source: University of British Columbia

Hummingbirds are among nature's most agile fliers. They can travel faster than 50 kilometres per hour and stop on a dime to navigate through dense vegetation.

Now researchers have discovered that the tiny birds process visual information differently from other animals, perhaps to handle the demands of their extreme aerial acrobatics.

"Birds fly faster than insects and it's more dangerous if they collide with things," said Roslyn Dakin, a postdoctoral fellow in the UBC's department of zoology who led the study. "We wanted to know how they avoid collisions and we found that hummingbirds use their environment differently than insects to steer a precise course."

Scientists at UBC placed hummingbirds in a specially-designed tunnel and projected patterns on the walls to figure out how the birds steer a course to avoid collisions when they are in flight. They set up eight cameras to track the movement of hummingbirds as they flew through a 5.5-metre long tunnel.

"We took advantage of hummingbirds' attraction to sugar water to set up a perch on one side of the tunnel and a feeder on the other, and they flew back and forth all day," said Douglas Altshuler, associate professor in the department of zoology. "This allowed us to test many different visual stimuli."

While not a lot is known about how birds use vision in flight, it is known that bees process distance by how quickly an object goes past their field of vision, like we do as we drive down a road. As we pass by telephone poles on the side of the road quickly, our brains understand that the objects are nearby; buildings in the distance will take some time to pass, letting us know they are further away.

When scientists simulated this type of information on the tunnel walls, the hummingbirds didn't react. Instead Dakin and her colleagues found that the birds relied on the size of objects to determine distance. As something gets bigger, this may signal to the birds that they are getting closer, and as something gets smaller, it may signal that they are moving farther away.

Continued …

What Does A Bird See?

Commentary by Mari Carbajal

MARI CARBAJAL | THURSDAY, MAR 31, 2016

There’s an abundance of bird species, most of which have specialized traits that help them get through their day.

Not all species of birds have large talons to catch their prey, or are able to drill a hole to hide their food. But no matter what species you choose to examine, all birds share one unique visual capability – the ability to see the standard color range, but also the reflective ultraviolet light spectrum.

This unique sense is crucial for finding food, locating a mate, spotting prey, and a whole lot more.

Cones in the retina of the eye are cells responsible for detecting color. Humans only have three cones (red, blue and green), but birds can have four cones or more, depending on the species. This allows them to see within the spectrum of ultraviolet light.

Birds that are active during the day have better detection of color than birds active at night. Nocturnal birds such as owls have a larger number of cells that allow them to enhance their sight in low-light conditions. They might not see colors as clearly as diurnal birds, but having more rod cells lets in more light.

Having such an exceptional sense certainly changes a bird’s perspective on everything in its environment. Birds can see visible colors more distinctly than a human because each cone in a bird’s eye holds a drop of colored oil that selectively filters out specific colors. This is similar to how a camera lens works. It gives the bird greater sensitivity to shades of colors. In turn, it allows the bird to visualize contrast in its surroundings. It then gives them the ability to see through other prey’s camouflage.

Continued ...

Small birds have vision twice as fast as humans: Study

Sat, 19 Mar 2016-06:15pm , PTI

Did you know this?

The vision of small perching birds in the wild is twice as quick as humans and faster than any vertebrates, according to a new study.

Researchers from the Swedish University of Agricultural Sciences, Uppsala University and Stockholm University in Sweden studied the ability to resolve visual detail in time in three small wild passerine species - blue tit, collared flycatcher and pied flycatcher.

The ability is the temporal resolution of eyesight, that is the number of changes per second an animal is capable of perceiving. It may be compared to spatial resolution (visual acuity), a measure of the number of details per degree in the field of vision, researchers said.

They trained wild-caught birds to receive a food reward by distinguishing between a pair of lamps, one flickering and one shining a constant light.

Temporal resolution was then determined by increasing the flicker rate to a threshold at which the birds could no longer tell the lamps apart.

This threshold, known as the CFF (critical flicker fusion rate), averaged between 129 and 137 hertz (Hz). In the pied flycatchers it reached as high as 146 Hz, some 50 Hz above the highest rate encountered for any other vertebrate, researchers said.

For humans, the CFF is usually approximately 60 Hz. For passerines, the world might to be said to be in slow motion compared with how it looks to us, they said.

Continued …