Flight restriction impacts physical health.

As I said in my “Built for Flight” section, parrots do a lot of flying in the wild.  If we prevent them from flying or greatly limit their flight through wing clipping/wing trimming, insidious health issues can arise.  A bird who doesn’t fly makes precious little use of its flight muscles–the flight muscles that are supposed to account for 25-35% of its total body mass.¹  And what happens to muscles when they aren’t used?  They atrophy, or waste away.  One study compared the pectoralis muscle strength of birds before and after forty days of total flight restriction.  The results showed that pectoralis muscle strength had decreased significantly in those forty days.²

These images show the electrical activity of birds’ pectoralis muscles before and after forty days of flight restraint. The marked change in strength is apparent. (Source: see footnote 2.)

Muscle atrophy is caused when an inappropriately low mechanical load is placed upon a muscle.  This can be due to the reduced gravity of space flight, bed rest, immobilisation, or disuse.³  Muscle loss also occurs as a natural part of aging, but physical activity helps prevent this.⁴  Those perch-bound birds you may seen have atrophied flight muscles.  It can take months or even years to rehabilitate a previously clipped bird, depending upon the severity of the clip and how long it was clipped for.  Sometimes, they never truly regain correct posture or control while flying.  Research in both mice and humans has shown that it gets harder to recover from muscle atrophy as an animal gets older.⁵

This greenwing macaw was clipped before fledging and remained clipped for the first 21 years of his life. It took him about 2.5 years to grow all of his flight feathers back once he went to a new home and stopped being clipped. He never voluntarily flapped his wings. At 24 years old, his new owner began running in the house with him to encourage flapping. In this video, he aims for his cage and his owner lets him go.  Sadly, his muscles are so weak from disuse that in the space of a few feet he loses almost all of his height. After practising encouraged flapping for about eight months, this macaw started voluntarily flapping. He has yet to attempt any flight on his own, even to earn treats during target or recall training. His owner is going to try with even shorter distances and hopes to get him flying eventually.  Credit: 1Tale4Paws on Youtube and Instagram.

Bone health can also be affected by lack of exercise.  Dr. Scott Echols, avian veterinarian, has observed trends in bone disease among his patients.  He found that physical inactivity plays a role in decreased bone density and recommends that pet birds perform bone-loading activities such as flying, climbing, and walking.  All three activities contribute to bone health; birds who don’t fly tend to have weaker bones in certain areas of their bodies.⁶  His observations make sense, of course, because bone disuse leads to bone loss.⁷  A clipped bird does not often use its wings; using them in a weight-bearing capacity is even rarer.  While there are partial wing clips which allow birds to achieve some flight ability, these still have visible effects on a bird’s posture.  Whether this posture may, over the course of years, affect their spine and cause discomfort has not been studied, but it is certainly something to consider. What if a human were to constantly walk stooped over due to a heavy burden placed upon their back?  That person might be “working harder”, but the burden would force them into an unnatural posture and almost certainly cause pain, if not more serious orthopedic issues.  It seems logical to assume that maintaining a correct and natural posture while flying would be more comfortable and healthier for a bird in the long-term.

This cockatiel demonstrates the impaired posture of a bird who is clipped but retains some flight ability. Because he is struggling to generate enough lift to keep his body airborne, his back end droops and gyrates in a front to back motion.  A parrot with unaltered wings carries its body parallel to the ground and does not struggle to keep its back end level with its head.  Credit: Alicia K.

If observing this cockatiel and the previous one at full speed, someone inexperienced with parrot flight might think that both birds are flying in more or less the same way. In slow motion, however, there is a clear difference between the two. The second bird, of course, is fully flighted and exhibits natural posture and control.  Credit: @_ruby_the_cockatiel_ on Instagram.

Heart disease is incredibly common in pet parrots.  A study performed on 107 deceased captive parrots found that 36% of them had visible gross lesions of the heart or major vessels, while 99% of them had low-grade abnormal changes to the heart or major vessels.  49% had an accumulation of fat cells in their cardiac muscle.⁸  In an earlier study on 269 deceased captive parrots, 10% had visible evidence of heart disease, and congestive heart failure was the probable cause of death for 6% .⁹  Research on zoo birds revealed that 90% had fatty streaks and fibrous plaques in their arteries, while 24% had lesions associated with atherosclerosis (hardening and narrowing of the arteries).¹⁰  This study points out that “parrots usually do not show clinical signs of atherosclerosis, and the most common sign is believed to be sudden death”.  Yet another study on zoo birds found that small birds, such as finches, sparrows, doves, and parakeets, had a much lower incidence of hardened arteries; these birds were kept in enclosures that allowed them to maintain a high level of physical activity.  Hardened arteries were seen more commonly in larger birds which the authors note had little opportunity for natural activity and behaviour, such as ducks, geese, macaws, cockatoos, hawks, eagles, and storks.¹¹

Left: Arrows point to thickening and discoloration on the heart of a deceased African grey with arteriosclerosis. Image from Clinical Avian Medicine.  (See footnote 13.)  Right: Atherosclerosis in a budgerigar’s aortic wall as seen under a microscope (x100 magnification).  In this study, seven birds without any visible heart abnormalities were found to have atherosclerosis upon microscopic examination.  The authors write, “These findings emphasize that the diagnosis of atherosclerosis cannot be based solely on macroscopic findings”.  (Source: see footnote 8.)  Thus, the heart may look healthy even while fatty buildup and other harmful changes occur.

The main risk factors associated with heart disease in captive birds are, according to researchers and avian veterinarians, “Lack of exercise, obesity, and nutritional deficiencies”.  (Source: see footnote 8.)  “Inactivity and social stress caused by the inability to exhibit natural behavior…”  (Source: see footnote 10.)  “Lack of exercise, inappropriate diet, and abnormal environments”.¹²  A comprehensive text on avian cardiology written by four veterinarians states that “Proper flight exercise and diet will prevent obesity, a major contributor to this cardiac disease [atherosclerosis]”.¹³  Obesity increases risk of developing not only heart disease, but a myriad of health issues, including fatty liver disease ¹⁴, ¹⁵, ¹⁶, kidney disease¹⁷, diabetes¹⁸, hypertension¹⁹, osteoarthritis²⁰, difficulty breathing due to air sac compression²¹, foot lesions²², and egg-binding²³, among others.  (See footnote 14 for a veterinary source which lists each of these health risks associated with obesity.)  Nutrition is surely a concern when it comes to preventing heart issues and obesity, but why would we make it harder on our birds to be healthy by not allowing them to exercise in a way that is most natural for their bodies?

This blue and gold macaw is 29 years old and has never flown, having likely experienced flight restriction before fledging. She began plucking when she was 19. Her owner has tried some flapping exercises with her, but they unfortunately cause so much discomfort (most likely due to the pain felt by using muscles she has not used in decades) that she plucks her shoulders after energetic flapping. Birds with this much atrophy can require gentle wing-stretching exercises before progressing to flapping. Her inability to properly flap has been a source of great sadness for her owner, who bought her when she (the bird) was 14. Having learned in recent years about the importance of flight and the effects of wing clipping/wing trimming, she hopes to rehabilitate all of her birds to a lifestyle that includes at least some flight. As seen in the video, this bird has recently started attempting some light flapping. NOTE: DO NOT TAKE YOUR BIRD OUTDOORS UNRESTRAINED, CLIPPED OR NOT.  THIS VIDEO IS FOR ILLUSTRATIVE PURPOSES ONLY. Credit: 1Tale4Paws on Youtube and Instagram.

You may have heard the argument that getting a bird to flap its wings is “enough exercise”, but flapping wings rather than flying is not a sufficient mechanical load for an animal which naturally relies on flight to get around.  Take a look at the image below this paragraph and note the difference in aerobic exercise a bird experiences when it flies compared to when it walks.²⁴  Even while vigorously flap-running at a steep angle, a bird uses less than half the energy it does during level flight.  Compare more modest flap-running to ascending flight and the bird uses only 10% as much energy.²⁵  Non-flighted locomotion in a flighted bird is an energy-saving strategy, not a way to get a workout.  A clipped bird flapping its wings is not truly exercising, even if it is panting and seems tired afterward.  In fact, this is indicative of poor physical fitness, similar to a human who becomes worn out after walking from the store to their parked car.  Exercise is healthy for so many reasons, even beyond the ones I’ve already mentioned.  It enhances immune system competency²⁶, induces brain plasticity²⁷, and helps alleviate depression and anxiety.²⁸

Compare heart rate and oxygen consumption when a bird walks to when a bird flies.  It is clear which provides more of a cardio workout.  (Source: see footnote 24.)  This study was done on geese, who are arguably better at and more suited for walking than parrots.  If this study were done on parrots, I believe the disparity would be even greater.

Furthermore, studies on budgies have shown that daily flighted exercise is important for the proper function of a bird’s defences against oxidative stress.  Highly reactive atoms, called free radicals, cause damage to living cells.  They are byproducts of normal cellular function, but they can also enter the body through pollution, radiation, and certain drugs.  In order for an animal’s body to combat these free radicals, it needs antioxidants.  Some antioxidants come from diet, but others are produced within the animal’s own body.  When the damage overcomes the body’s defences, disease processes occur.  Many age-related diseases are associated with oxidative stress.  In fact, oxidative stress is now considered one of the main causes of aging, and it interferes with the immune system in harmful ways.²⁹  The budgies in these studies who performed flighted exercise daily for nine weeks had less oxidative stress than the budgies who were mostly sedentary and then performed a single bout of exercise.  There was quite a difference in oxidative stress between the birds who had only been flying daily for a week and the birds who had been flying daily for over two months.³⁰  Budgies who were more active in their small cages—walking, climbing, hopping, performing the little flight they could–actually had more oxidative damage than the budgies in small cages who were less active.³¹

In this budgie study, MDA levels were used as an index of oxidative damage. Oxidative damage decreased with daily flighted exercise training. (Source: see footnote 30.)

This may seem confusing at first.  Didn’t I say that exercise protects rather than harms?  Exercise itself generates free radicals even while it produces antioxidants and conditions the body to deal with oxidative challenges.  “Therefore, excessive physical exercise is detrimental to untrained individuals, but progressive training allows the cells to more easily detoxify a larger amount of ROS [type of free radical].”³²  The walking, climbing, hopping, flapping, and even short flights failed to protect against, and only caused the birds more, oxidative stress because the exercise they were performing was not sufficient for their bodies to respond appropriately.  The authors of these budgie studies recognise this and suggest that even cages that allow for short flights and the stretching of wings may not be enough to allow birds to obtain the benefits of exercise-mediated antioxidant systems.  (Source: see footnote 31).  If short flights weren’t enough, how could no flight at all be enough?  When someone attempts to exercise their clipped bird by making it flap and then places it back on a perch, their intention may be to improve the bird’s cardiovascular health but, according to these studies, they may actually be causing higher levels of oxidative stress in the process.  This is not to say that a clipped bird should be allowed to let its breast and wing muscles fall into complete disuse, but it does underline the importance of allowing birds to exercise the way nature intends them to.