Birds have upper and lower eyelids that close to protect their eyes and prevent them from drying out, much like our own eyelids. In addition, they have an extra or third eyelid called the nictitating membrane. The extra eyelid is hinged at the inner corner of the eye and sweeps horizontally across the cornea. The word ‘nictitating’ comes from nictare, which means ‘to blink’ in Latin. A bird blinks by sweeping its semi-transparent nictitating membranes across its eyes, while its eyelids generally remain open.

Blinking helps to keep the eyes clean by removing dust and moistening and cleaning the cornea. This is especially important when there is a chance the eye might be scratched or damaged, such as when flying through dense vegetation or diving underwater to capture prey. Nictitating membranes are not unique to birds; they have been described in many vertebrates, including sharks, amphibians, reptiles and some mammals such as ungulates (large mammals with hooves). In ungulates, the nictitating membrane protects the cornea from being spiked by grass when the animal is grazing. Given that blinking makes the bird or animal temporarily blind, birds and other animals have limited visual information during blinks. Because of this, we would expect birds to strategically adjust their blinking behaviour.

In 2017, Guy Beauchamp, an independent researcher based in Canda, investigated intermittent blindness when domestic chickens are feeding. His study aimed to examine the extent to which blinking occurs during feeding bouts in domestic chickens. Beauchamp was also interested in the effect of group size on blinking. His hypothesis was that feeding effort tends to increase in larger groups, which could lead to increased intermittent blindness in larger groups of chickens. In the literature, it has long been thought that feeding with the head down compromises peripheral vision and increases predation risk.

Beauchamp’s study found that chickens blinked at a higher rate when feeding alone or in pairs. The chickens were functionally blind for nearly half the time when feeding. Blinking appears to be a cost associated with feeding because it is used for finding food visually. For foraging birds such as chickens, it is important to have many eyes scanning for threats, and Beauchamp’s study found intermitting blinking increases with group size. This is because foraging chickens rely on the combined efforts of other members of their flock to be vigilant for predators. Individuals experience higher predation risk in smaller groups and lower blink rates will maximise their ability to detect threats. In other words, chicken blink less when exposed to risky situations to minimise the chance of missing critical information.

What about blinking in flight? Because flying is dangerous, owing to the risk of collisions and crashes, it is especially important for birds to remain alert in fight. Blink duration was found to be relatively brief, and the nictitating membrane did not sweep across the entire eye. In such instances, the nictitating membranes could partially lubricate the eyes or clear foreign debris while minimising visual interference. A 2020 study by Jessic Yorzinski from Texas A&M University, USA, investigated this in songbirds. Dr Yorzinski used captive great-tailed grackles – a medium-sized, highly social passerine bird native to North and South America – to test blinking before, during and after flying a short distance in an open environment. The grackles were fitted with a two-camera system that continuously recorded its eye movements, including when the bird blinked.

Because individuals need to be highly alert in flight to avoid collisions, Dr Yorzinski predicted that the grackles would blink less. The result supported Dr Yorzinski’s prediction that grackles strategically modify their blinking behaviour in flight by blinking the least during take-off, flight and landing. They blinked the most at impact. Because they probably experience visual impairment during blinks, by minimising the time they spend blinking during flight the birds were likely maximising the visual input they received.

Some birds even have eyelashes to further protect their eyes. These bristle eyelashes protect the eye by inducing reflex blinking when touched. Not many birds have eyelashes, showing how effective the nictitating membrane is, but a well-known species is the African secretary bird. Their eyelashes are not like ours; instead they are made by specialised feathers in which the shaft (rachie) lacks a barb. Much more common than bristles are caruncles (skin features such as combs, earlobes, snoods and wattles), which are often brightly coloured. Bare skin around the eyes, eye rings and irises are also often brightly coloured, as we see in galahs. This colouring is likely driven by the need to attract the opposite sex. Having large or bright and colourful caruncles indicates that a birds has high levels of testosterone, is well fed, can elud predators and therefore is showing good-quality genes.

What does a bird see when they look at their own reflection? Do they see themselves or another bird? In several bird species, when they see their own reflection they seem to assume they are seeing a competitor and attack the image. Kookaburras, magpie-larks and fairy-wrens are among the birds known to attack their reflection in a window or car’s side mirror. This is usually a territorial behaviour that occurs mainly in the breeding season: the bird sees its own reflection in the glass as a rival it needs to drive away.

Scaring the bird away from the glass does not work because the bird’s impulse to  find the rival and chase it out of the area is powerful. The rival seems to be mocking the bird, attacking it back. Before we label the bird as stupid for doing this, remember, birds do not expect to encounter perfect reflections of themselves. They believe they are seeing another bird. Just as some birds consistently and persistently attack their own reflections, other birds respond to the image like a fellow flock member. They will even display flock mating behaviour, while perceiving a response in kind from the other bird!

At the root of this question is self-recognition – does a bird recognise itself in a mirror? Are birds self-aware? A crucial step of self-recognition is understanding that your own mirror reflection does not represent another individual but yourself. In humans, the ability to self-recognise in a mirror develops at about 18 months of age and coincides with the first signs of social behaviour. To help understand if animals recognise themselves in a mirror, we can look at Gordon Gallup’s pioneering work carried out in the 1970s. Gallup developed the mirror test, also known as the mark test or mirror self-recognition test. The idea is that you put a mark on a bird when it is unconscious in a location on its body that it cannot see without using a mirror, then watch to see what the bird does when it wakes up and sees itself in the mirror. If it touches the mark or tries to position itself to get a better view of the mark, you can be reasonably sure that it recognises the image in the mirror as itself.

In 2008, Helmut Prior and colleagues at Goethe University, Germany, applied this self-recognition test to European magpies (in the corvid family). In their study, the researchers applied red, yellow or black sticker spots on the necks of five magpies. The magpies could only see the stickers using a mirror; the sticker’s feel on their necks did not seem to alarm them. The result found that once the birds with coloured neck spot caught a glimpse of themselves, they scratched at their necks. This gave a clear indication that they recognized the image in the mirror as their own. Those that received a black spot sticker, which was invisible against their black neck feathers, did not react. Another study by Lisa-Clair Vanhooland, Department of Cognitive Biology, University of Vienna, Austria, using sticker spot on carrion and hooded crows (also members of the corvid family), however showed that the birds investigated the mirror with a pronounced and lasting interest. While some crows showed contingent behaviours in front of the mirror, none of them passed the mark test.

Amaan Buniyaadi and colleagues from the Department of Zoology at the University of Felhi, India, investigated self-recognition in Indian house crows in a 2019 study. They found that most crows (four out of six crows) responded to their mirror reflection as a self-image, because they attempted to remove the coloured mark by using their beaks or claws during the test. Of course, the test is not perfect. Some birds may notice the mark and just not care. Others may not use vision as their primary sense, with less of their brains devoted to processing visual information. Because of these limitations, negative results do not necessarily imply that birds fail to recognize themselves in the mirror.

What about parrots and cockatoos? Very little work has been done on these species in terms of self-recognition. One study, published in 1995 by Dr Irene Pepperberg from the University of Arizona, USA, on African grey parrots, found that time in front of the mirror resulted in several different reactions, including beak wrestling, talking and tapping on the mirror with their beaks. When the mirror was placed vertically, it produced a more aggressive reaction wherein the parrot attack its own reflection. The parrots failed the test! Clearly, we need to do more research in this area, especially with Australian corvids and parrots.

You may be surprised to learn that mirrors are not recommended for cage birds. Owners of budgies and other captive birds often provide them with mirrors or mirror-related toys as a substitute for social interaction. Despite their widespread use, exactly how mirrors relate to social behaviour in budgies remains a mystery. A 2017 study by Daniel Buckley and colleagues from Saint Joseph’s University in Philadelphia, USA, explored the relationship between social behaviours and mirror use in highly gregarious budgies. The study found an initial lack of mirror use, which is inconsistent with the interactions of parrots as discussed earlier. Moreover, these results also align with the idea that budgies perceive their reflections as another bird; therefore, they may take longer to approach this novel stimulus. Further results from the study show a relationship between pair-bond behaviour and mirror use; that is, budgies with a stronger pair bond may use the mirror, because the mirrors provide the illusion of a stable partner. Kind of sad, don’t you think?   

The first time you see a bird sunbathing, or sunning, you could easily believe the bird to be injured, sick or even dead. This is because a sunning bird will spread out in  full sunshine to expose its plumage and skin to direct sunlight. Hundreds of species engage in this activity. While birds typically sunbathe on the ground, they will sometime perch up high in a tree or on a roof – any open area with unobstructed sunlight and no shadows is a preferred spot. However, birds can also be seen sunning themselves in small patches of sunlight. During a sunning session, a bird may stay in the same position or it may change positions to expose different parts of its body to the sun. Different birds will sun themselves in different ways, but common sunning postures include standing with their back to the sun; fluffing the head and back feathers to expose skin; stretching, spreading or dropping the wings; spreading the tail; raising wings to expose underparts or flanks; and lying in a sunny spot with one or both wings outstretched.

Sunning behaviour has been noted as early as 1831 by John James Audubon, when he described a great white heron that ‘will sometimes drop its wings several inches as if  they were dislocated’. Today, we know that more than 50 bird families sunbathe, including birds of prey, doves/pigeons, songbirds, corvids and parrots/cockatoos. There are several theories about bird sunning behaviour and we know that birds sunbathe for different reasons. During cold weather or early in the day, birds sun themselves for warmth. This lets them maintain their body temperature without expending as much energy from food, increasing their chances of survival in cold climates or when food is scarce.

Sunning can also help birds convert compounds in their preen oil (secreted from a gland at the base of the tail) into vitamin D, which is essential for good health. If the birds have been in a birdbath or swimming, sunning can help to dry the feathers more quickly so they can fly without being weighed down by excess water. Some birds may even sun themselves for pure enjoyment and relaxation, much the same way that humans sunbathe. Many birds are observed sunning even on the hottest days, so sunning may also fulfil purposes other than temperature regulation.

One of the most important reasons for sunning is to maintain feather health and sunning forms part of a bird’s routine feather maintenance which takes up about 10% of the bird’s time. Sunning can dislodge feather parasites, because the heat will encourage the insects to move to other places in a bird’s plumage. This gives the bird easier access to remove those parasites; frequently, birds are seen preening immediately after sunning. They need to remove these parasites because the tiny insects damage feathers, which can cause problems for a bird’s flight insulation and appearance, all of which can impact its survival.

To help maintain their feathers, birds use their bills to remove dirt, mud and other impurities from their feathers, including unwanted parasites such as feather lice. Feather lice are about 1 mm long, and are biting insects that can easily spread between birds. The lice are skilled at hiding among a bird’s feathers so they can be hard to remove by preening alone. Because sunbathing birds can get very hot – as much as 71 degrees Celsius – the lice are burned alive. In this way, the short blasts of heat and/or ultraviolet (UV) radiation from the sun’s rays work as a non-chemical pesticide.

A bird may sunbathe immediately after a dust bath as it continues its extensive grooming regimen. When a bird dust bathes, it adapts erratic motions and crazy postures to raise a cloud or dust, which gets worked into the feathers to absorb excess oil. This oil-soaked dust is then shed easily, which keeps the feather clean and flexible for more aerodynamic flight and efficient insulation. Along with the dust, dry skin and other debris get removed. In the semi-arid and arid habitats of hot countries for bathing may be scarce. A bird may dust bathe anywhere and at any time, when it needs to keep its feathers well groomed and when a suitable patch of dust or dry dirt is nearby.

Next in the grooming regimen is anting. Have you heard about anting? This is where a bird either sits on an ant nest or places ants in its plumage, possibly to rid itself of parasites. There are two types of anting: active and passive. Both behaviours help with moulting, smoothing skin irritation during rapid feather replacement, which is why anting is most common in late summer and early autumn. Anting also controls parasites such as biting lice and feather mites, which live in the inner catacombs of a bird’s plumage.

Active anting is when a bird holds an ant in its bill, spreads and lowers its wings and brings its tail forward between its legs, wiping its outer wing and tail feathers with the ant. Passive anting is when the bird crouches on an anthill with its wing and tail feathers spread, allowing ants to crawl freely throughout its feathers. The ants that birds use for anting come from two subfamilies that are stingless and produce defensive secretions to repel attacks. Ants from the first and largest subfamily Formicinae (mostly Formica, Lasius and Campmnotus) produce formic acid which they eject from the tips of their abdomens. Ants in the second subfamily, Dolochoderinae, secrete a repugnant oily liquid from their anal glands. A 2005 study by N.S. Morozov from the Russian Academy of Science found that when birds were offered ants with the formic acid sac removed, the birds ate the ants immediately. When intact ants were offered, most were used for anting. Clearly, the ant’s formic acid sac was a trigger for anting to occur.

Keeping feathers healthy takes maintenance and a good preening regimen; therefore, it is a good indicator of bird health. A sick or injured bird often has a ‘scruffy look’, with feathers out of place; other birds notice and are not impressed. The birds may be excluded from the flock until it cleans itself up. This is why you will often see birds washing themselves even on wet days. When you live in a tight social group hygiene is important!

When we think of a bird wagging its tail, we often think of the willie wagtail, a member of the fantail family. But many bird species show tail movements, called wagging, flicking or pumping. This happens when a non-flying bird moves its tail independently from the body. In several birds species, tail wagging is commonly used in sexual display behaviour, as seen in lyrebirds and peacocks. What about magpies – do they wag their tail? Magpies combine tail wagging with a bow down, which can be a signal of submission displayed when a subordinate bird is in the presence of a dominant bird. In different species, tail movements may serve different functions, depending on the bird’s behaviour, feeding place, foraging tactics and social nature. When watching a tail-wagging bird, pay attention to the tail’s length, its feather structure or contrasting colour pattern, because they can all relate to tail movement.

But back to the question. Commonly found in urban parklands and suburbs areas, willie wagtails are ground-feeding insectivores that prefer an open habitat with access to cleared areas such as open lawn. The species gets its name from its well-known tail-wagging behaviour, in which the bird rapidly moves its tail horizontally when foraging. Wagtails are highly aggressive, even fearless when defending their territory. They will harass not only small birds but also much larger species, such as magpies, ravens and even wedge-tailed eagles. They have signals to show their moods. When a bird’s white eyebrows become flared and prominent, it is an aggressive display warning to others. Their eyebrows before more hidden when the bird is submissive or relaxed. The bird is almost always on the move; it is rarely still for more than a few moments, spending much of its time foraging on the ground. We are still not sure what the function of tail wagging is. It may assist with flushing insects that are well hidden from the ground because flicking occurs more on the ground than when sitting on a perch.

A 1993 study by Janey Jackson and Mark Elgar from the University of Melbourne supports the idea that tail wagging may flush out insects. The researchers suggest that the moving tail causes rapid changes in light intensity, thereby startling the insects. The probability of an insect being flushed depends on the contrast in light intensity casting a shadow and the frequency with which these changes occur. This led Jackson and Elgar to speculate that if the main reason for tail wagging was to flush insects, then wagtails should adjust their tail-wagging rate to maintain constant food intake under different conditions of light intensity. If tail-wagging rates were lower in bright sunny conditions and higher on dull overcast conditions, there should be no difference in the tail-wagging rates of birds foraging on overcast days or in shaded areas on sunny days.

So what did the study reveal? The study found that wagtails neither flashed nor fluttered their wings when on a perch, suggesting that wagtails commonly use perches as vantage points to scan flying insects. In contrast, when foraging on the ground, tail wagging varied according to whether the birds were foraging in bright sunlight or shade. Wagtails foraging in the sunlight wagged their tail at less than half the rate of birds foraging in the shade on sunny or overcast days. The similarity of the birds’ tail-wagging rates when foraging on overcast days and in the shade on sunny days suggested that light intensity rather than weather conditions determined the tail-wagging rates. The researchers concluded that tails are wagged less frequently under brighter conditions, possibly because insects are more easily startled by the bird’s shadow. An insect may detect the jerky movement associated with tail wagging causing it to take flight.

In addition, wagtails are often seen waging their tails when foraging in close proximity to both wild and domesticated animals on pastures and grasslands. The birds either run behind or next to a moving animal, capturing insects as they are displaced or even take then straight from the animal’s back. An unusual foraging tactic of wagtails was described by Carlos A. Delgado and Juana Correa-H from the School of Biological Science, University of Wollongong, in 2013. The researchers observed two wagtails following a horse, provoking it into shaking its head quickly and walking away because of the persistent birds. Throughout the researchers’ observations, the wagtails succeeded in forcing the horse to move. Each time after antagonising the horse, the wagtails were consistently seen capturing insects close to the horse.

The researchers interpreted the birds’ swooping behaviour as being intended to make the horse move to flush insects. The horse ignored the presence and movements of the birds on its back but immediately responded with irritation when a bird was at its ears. The bird only swooped when the horses did not graze or walk and stopped once the horse walked. Once the horse began grazing again, the bird returned to capture insects and the swooping did not occur while the horse was actively grazing. This suggests the wagtails knew what they were doing. Isn’t that just brilliant? They are great birds and seriously smart!