The most common causes in the wild for birds loosing a leg is entanglement with thread, fishing line, balloon ribbons or other litter. This can happen at all ages, even as a nestling. Other causes include predator attacks, birth deformities or injuries caused by traps and snares.
It is very likely that wild birds loosing a leg in the wild will not survive. This is mostly due to the trauma itself, subsequent weakness, other accompanying injuries, blood loss or secondary infections. However, some birds seem to adapt amazingly well to being one-legged. Life is definetly more challenging for a bird with one leg. These birds often lose their mates or have more difficulty to find a partner, particularly if the species’ courtship display requires both legs. If the bird requires two legs to forage, or is using two sets of talons to capture prey, then they must either adapt very quickly or they will starve and die. Naturally, one-legged birds are more vulnerable to become prey to predators and their lifespans are typically shorter than birds without a physical impairment. This clearly shows that only a very few bird species will, at least theoretically, qualify for release after successful rehabilitation following a leg or foot amputation. Some bird species, such as swans and ducks may do well in semi-wild settings like parks or places with artficial feeding sources, safe shelter places or islands. However, one should bear in mind that these waterbird species have a great advantage, compared to other bird families, such as corvids or birds of prey. They are all able to spend a considerable amount of their lives on the water, which will relieve the stress and pressure the healthy leg is normally exposed to when on dry land, considering in particular the fact that these birds are quite heavy, which makes them especially prone for pressure sores.
Birds that adapt most readily to losing a leg are generally omnivores that can take advantage of multiple food sources. Birds who do not need to migrate do also have an advantage, as they do not have to deal with the stresses of migration. Birds in urban or suburban habitats may adapt more easily because of the availability of feeders, food scraps and bird-friendly gardens that provide ample resources. Because physically impaired birds are more vulnerable to predators, they prefer safe and secure shelter near any feeding area. That is why it is relatively common, that these birds may stay in places, where they find this kind of shelter and support, as they often do in gardens of bird loving people, which in itself creates a degree of dependency.
So, what about a rescue bird, who underwent a leg or foot amputation? A rescue bird obviously went through surgery and recovery under ideal conditions, enjoying pain relief and a safe environment, unlike his or her wild counterparts. This also means that the adaptation process is very different, as food and shelter have been provided for free and without any effort or energy loss normally occuring in the wild. Rescue birds do not need to travel for food or fight against food competitors. They do not need to be able to integrate into their respective social bird hierarchy. These are all factors, which in the wild would require energy reserves and perfect fitness. Understandably, it is also very difficult to prepare a captive bird to successfully tackle these problems, as this kind of training and exercise is diffcult to provide to the extent required in the wild. Even the recommended soft release option becomes rather a hard release under these circumstances.
Additionally, there are even more factors to consider when caring for physically impaired birds, factors which do have a great impact on the quality of life in captivity and in the wild, and which influence directly the survival chances of these birds. These problems become even more important, when birds are not perfect flyers, for example due to a suboptimal or damaged plumage, or when they are getting older and become less mobile. With regards to the ability to adapt, corvid species such as jackdaws are more likely to cope with a foot amputation or joint stiffness, which is mainly due to their low body weight. Heavier birds, such as crows and rooks, may also cope relatively well, in particular when young and strong. However, one should not forget that being young and strong does not last forever, which means that birds coping well at the time of release may get into great difficulties when getting older or when weather conditions are becoming less favourable.
Unlike in the wild, in captivity it is possible to counteract most of these potential problems by adapting aviaries and enclosures accordingly. Perches can be replaced with flat padded wooden boards, which allow the bird to sit and rest comfortably and also help to avoid the precious plumage being damaged or soiled. Roosting platforms can be carpeted with non-slip thick artificial grass mats, which can be easily replaced and hosed down daily. Physically impaired birds in captivity need to be monitored very closely, and a weekly bath with lukewarm water may become part of a normal routine, as these birds sometimes may struggle to preen themselves efficiently, in particular when getting older. Access to food and water can be easily guaranteed in captivity, as competition with other inmates can be avoided by providing ample food and feeding opportunities in different areas of the aviary. Keeping captive birds in groups also means that relationships between birds can be easily observed, bearing in mind that these relationships are never static but rather dynamic, as they would be in the wild too. Bonds and friendships may change during the lives of these birds. When keeping physically impaired birds, and despite optimal aviary preparation and design, there is always an increased risk and increased likelihood that foot and joint deformities as well as pressures sores may develop, which need to be avoided at all cost and do require frequent checks and health assessments.
So, how would a rescue corvid with leg or foot amputation cope in the wild? Due to their life style and ability to adapt, corvids would have an advantage as omnivores. They would be able to adapt to a certain degree, but would very likely stay in the soft release area and would therefore continue to rely on support feeding. Territorial corvid species such as magpies and carrion crows would have great difficulties to find a partner and to succesfully occupy and defend a breeding territory. They would also have to fight very hard for a favorable social position in non-breeding flocks, if they would attempt to join. Gregarious rooks may have an advanatage in this resepct. However, as rooks obtain most of their food by probing the ground, physically impaired birds may struggle to do so, especially in those areas where winter feeding is difficult or impossible due the ground being frozen, which will require that these birds would have to migrate. Generally seen, roosting may also pose a problem on a daily basis, as these birds will have some problems to perch properly.
Prior to any release animals should be considered fully fit and able to fend for themselves in the wild. Fitness assessment should consider clinical, behavioural and physical assessments such as weight, body condition score and the ability to fly or run etc. A release should not be carried out if animals are deemed significantly less likely to thrive in the wild than a conspecific. All in all survival chances of one-legged corvids will not be very good, in particular not in the long-term. Their life expectancy will be far lower compared to their two-legged counterparts. On balance we would not recommend the release of one-legged corvids, especially not when considering the fact that one-legged birds are by defintion not in full health and have therefore a limited physical ability, compared to their wild counterparts. From an ethical standpoint, it could be regarded as cruel, whilst from a legal point of view it would most likely be regarded as illegal to release a bird, who has a low chance of survival in the wild compared with his or her conspecifics.