Some bird species have an expanded, thin-walled offshoot or pouch in the oesophagus, which is called the crop. The crop is being used to store food before it is being transferred through the oesophagus into the stomach. Corvids don’t have a genuine crop.
However, all bird species, including corvids, have two parts to their stomach. The first part of the stomach is the proventriculus or glandular stomach, where digestive enzymes are secreted to initiate the process of digestion. The second part of a bird’s stomach is the gizzard or muscular stomach.
One of the most important aspects of corvid rehabilitation is the provision of a natural diet, environment and associations that ideally duplicate what corvids would be exposed to in the wild. This can be achieved by building and furnishing aviaries with this goal in mind. Since the majority of corvid rehabilitation deals with orphans, this approach is especially critical to releasing strong, robust, well-adjusted corvids that will go on to survive in the wild. However, theory and reality are as always slightly different. This is particularly true when corvids are being cared for longterm, which is quite often a necessity and will give them the best chance of survival in the wild. Sadly, in reality, many rescues will not give these birds the chance they deserve, because long-term rehabilitation is time consuming and financially demanding. Many of these birds will be either put to sleep straight away, or will even be prematurely released.
Basic Considerations Before Building A Corvid Aviary
Lets start with some basic considerations. When contemplating the aviary size, then experience shows that an aviary is never to big, but always to small, which becomes in particular obvious when furnished. When choosing the aviary location, one should make sure that it is easily accessible for caregivers, while keeping it away from public areas and pets. Corvid aviary materials are also of great importance, as corvids are generally very destructive. This means that these birds will definitely put any aviary to a test. Over time wooden rafters will be chiselled away, which automatically implies that wood preservatives being used have to be safe for birds. Wooden aviaries have to be continuously inspected to make sure that they remain safe, keeping birds inside and predators out. Metal aviaries are obviously more resistant, but are also more expensive and require generally more effort when it comes to furnishing them. The mesh size should also be chosen according to the species to be housed. Plastic mesh is not a viable option for any kind of corvid aviary.
It is well known that corvids will cache their food, which is going to attract not only rodents, but also insects, snails and slugs. In that context, it is important to understand that worms and other parasites are being transmitted by snails and slugs, which can seriously affect the health of all but in particular  recovering or immunocompromised birds. Cleaning up the cached food keeps your aviary clean and your birds healthy, but no necessarily happy, as corvids have their very own idea, what a tidy aviary and home should look like.
Planning The Basic Aviary Structure
It is advisable that a corvid aviary has at least two of its sides completely covered, to give birds a safe and sheltered place to retreat. Having the sheltered area away from the entrance door ensures that frightened birds will be able to move away from the person entering the aviary, allowing them to retreat towards the shelter area. Wooden panels work well, but other materials like fabric or synthetic sun shade and windbreak mesh, as used in greenhouses, can also be used. However, when using the latter, one has to bear in mind that corvids will most certainly tear and destroy these materials, and long pieces of twine will pose a strangulation hazard, if remaining undetected.
The aviary roof should be partly covered to protect the animals from the elements. But there should be also areas in the aviary, where birds are able to enjoy sunshine, rain or snow. Double entries or safety porches are definitely desirable, but will naturally decrease the available aviary space for the birds. Sheltered areas can be easily created by using straw or seagrass baskets, which work particularly well for smaller corvids like jays or jackdaws.
Choosing The Most Suitable Type Of Aviary Floor
When building an aviary, a common goal should always be to incorporate as many natural elements as possible, to create a natural habitat mimicking environment. However, the feasibility of this ideal case scenario depends on the number of corvids being kept. A meshed rat proof natural dirt floor with gras and bushes is certainly ideal, but more difficult to keep clean and hygienic. This problem increases proportionally with the number of corvids being kept. It is only a matter of time until a beautiful meadow is completely destroyed and bushes have lost all their leaves. Only very hardy plants, which have to be obviously safe for the birds, will survive, but does usually only for limited period of time. It might be necessary to replace or at least to rotate these plants on a regular basis.
In contrast, concrete flooring is easy to keep clean and to disinfect, but it is obviously not natural and can pose a health hazard for birds having temporary or permanent disabilities, like the ones being prone to falls. A compromise might be to create a concrete floor aviary with added confined areas of different substrates, like an area of wood bark underneath a common seating and roosting area, which dampens a potential fall. Artificial grass or astroturf might work as well, however, it can be difficult to maintain, especially when more than two or three birds are being kept in this aviary. There is also a risk of debris accumulation underneath grass mats. As said already before, it is also very likely that corvids will destroy and possibly eat parts of the grass mat or carpet being used, which can potentially cause gastrointestinal problems. Alternatively, one could also create a confined patch of natural gras, sand or grit, which provides a great playground, is slightly easier to maintain and to replace, which also avoids the buildup of contaminants. Depending on the size of the aviary and number of birds to be kept, it might be necessary to integrate a drainage system, which will help to maintain basic hygiene levels and will reduce the built up of contaminants being distributed beyond the aviary boundaries by water run off. This helps to keep aviary birds healthy and avoids cross contamination affecting other wild animal species living in the near vicinity.
Accessibility Considerations For Birds With Disabilities
When creating a sheltered area for birds to hide and roost, one has to always make sure that all birds are able to reach this area easily and safely. This also implies that the furnishing of the aviary has to be based on the abilities of the animal with the most severe disability. This makes sure that all animals can get to all essential aviary places like roost, shelter, bath and food without injuring themselves. One should also consider that disabilities may develop during the stay of animals patients, as quite commonly seen in birds with plumage problems caused by a nutritional deficiency, which may become completely grounded for a certain period of time, until they go successfully and undamaged through their main moult.
If there is a risk of limited mobility, even only for a short period of time, then it is crucial to consider a variety of different sized perches and perch materials to avoid the development of an ulcerative pododermatitis or bumblefoot, which is a bacterial infection and inflammatory reaction on the feet of birds. Padded perches or block perches will help to prevent this disease, keeping birds off the ground and the plumage pristine. Thick natural ropes can also be used, as they can help to bridge distances between different aviary levels. They also help birds to train their sense of balance whist being gentle to their feet and good fun to dismantle. Astroturf or outdoor carpet, which can be used as perch or stand padding, can be easily cut to size, but might be in need of frequent replacement. Wooden shelfs or planks, strategically positioned at different levels, trees trunks of increasing height, piles of tree logs or adapted wooden ladders can also help to bridge different height levels in an aviary.
Although a sufficiently sized bird bath is an essential part of any corvid aviary, one has to remember that the bath itself might pose a death trap for disabled birds. Positioning of the bird bath is crucial, not only to keep the bath clean as long as possible. The size and water level of the bath might need careful consideration, in particular when disabled animals are inhabitants of the aviary.
Entertainment And Enrichment For Corvids
Corvids generally need company of their own kind, which means that corvids should not be raised or kept by their own. All corvids species benefit from entertainment and enrichment being provided. Because corvids are generally neophobic, it might be helful to limit the number of new toys being introduced to a few at the time. As with children, it is certainly a good idea to remove old toys for a while and to reintroduce them at a later time. Toys do not have to be expensive, but natural materials should be a preference, in particular when dealing with wild releasable animals. Corvids love pebbles, stones and shells, which they like to use as toys, but also as a marker for cached food.
Other natural toys are pin cones, acorns, twigs and branches. Corn on the cob is a nice treat in particular for rooks and jackdaws, as it is also a very entertaining pastime. Cuttlefish bones are often very much appreciated and are useful too, as they serve as a natural source of essential minerals and help to trim the beaks. Half rotten tree stamps are most corvids’ favourite, as almost all seem to enjoy to dismantle them. A soft tree stem is also an open invitation to dig for worms and insects, and to hide food items in crevices and holes. Children’s wooden play cubes are often well accepted and appreciated as toys. Many corvids cannot resist crumbled paper balls or toilet paper cardboard rolls. However, as these items will most certainly end up soaked in a bird bath, aviary cleaning might become truly tedious. If dealing exclusively with captive birds, the spectrum of available toys becomes much larger, as long as they are deemed safe.
This is by no means an exhaustive list of considerations to make when planning and building an aviary for corvids, but it should hopefully give an indication of the complexity of issues and problems to consider. An aviary project gets rarely completely finished, it will more likely continue to remain an ongoing theme and might actually never come to an end. As soon as the first birds inhabit, explore and investigate the interior design of the new aviary, further changes and adaptations of the original design will most certainly become necessary.
Yesterday, we closed our release aviary doors, bringing this years’ carrion crow and rook release saison to an end. At the end of September we opened the aviary doors for 17 crows and rooks to be soft released. Â Out of these 17 release candidates, 15 birds, consisting of 11 carrion crows and four rooks, have been successfully soft released. Two birds decided to stay and will get another release chance offered next year. These two birds will join a group of birds in our communal aviary already being earmarked for release in autumn 2018. Â Out of these 15 released birds, we released three birds, who stayed with us since 2015, three birds, who came to us in 2016, and nine birds, who have been admitted in 2017.
Soft release is a release technique, which involves continuing care for animals at the release site, particularly back-up feeding, and requires a greater commitment of time and effort than a hard release does. Soft release is particularly important for hand reared animals, especially of species which need to learn about their surroundings and need to learn survival skills such as foraging and hunting. Â It is also appropriate for older immature or adult birds, who have been maintained in captivity for prolonged periods, or are being released at a site distant from their original location, as the original location might not be suitable.
Some of the released birds have joined straightaway our local mixed rook and jackdaw as well as non-territory holding carrion crow flock, which they already got to know very well during their stay with us. Both flocks are frequent visitors to our premises, a fortunate situation, which allows direct interaction and communication between wild birds, patients and residents. Over the past weeks some of the released birds decided to come back into the safety of the release aviary to roost, whilst others came back only to get some extra snacks. Many of them stayed in the near vicinity for longer periods of time. After becoming more and more confident, which is a learning process lasting anything between several days and many weeks, we could observe these birds, when they followed the local flocks flying further and further away from the release site, to participate in daytime activities and to eventually join the night roost.
Rook Atreo
Rook Bella
Carrion crow Castor
Carrion crow Corbyn
Carrion crow Harper
Rook Hugo
Carrion crow Joey
Carrion crow Justus
Carrion crow Magnus
Carrion crow Penthesilea
Carrion crow Stella
Rook Tadeas
Carrion crow Philander
Carrion crow Merilyn
Carrion crow Bertram
Although the aviary doors are closed now, backup feeding and shelter will still be provided throughout autumn and winter. Most of the released birds are now staying away completely, or at least for longer periods of time. Some of them  are still coming back to visit their old comrades or to enjoy some food, which we will continue to provide.
When checking out the picture gallery, you will find a short summary underneath every picture telling you a little bit about the individual stories of these fascinating birds.
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This short videoclip shows one of those beautiful occasions, where we were privileged to be part of the daily lives of our wild non-human animal neighbours. Just by chance we have been able to document and record a fascinating playful interaction or variation of social play occurring between a wild young rook and a mixed group of rooks and jackdaws as well as a small flock of residential pigeons circling the area. Just a few seconds after the rook had drawn the attention of one of the approaching jackdaws, the rook decided to disengage and to follow the leaving birds.
” Social play is an excellent example of a behavior in which many animals partake, and one that they seem to enjoy immensely. Individuals become immersed in the activity, and there seems to be no goal other than to play. As Groos (1898) pointed out, animals at play appear to feel incredible freedom. ” 1
Social play observed amongst non-human animals including corvids plays an important part in the emotional lives of many non-human animal species. During our daily interactions with our corvid patients, residents and visiting wild birds, we are frequently able to observe many of these intricate nuances of their fascinating emotional lives, and even get sometimes involuntarily involved in their playfulness and cheekiness. Although many encounters we are able to witness may serve a specific purpose, a purpose we may or may not fully understand, some incidents like the playing rook in the video clip, might just be what it seems – a bird having a bit of fun, nothing more and nothing less.
The list of animal exploitation is long and includes the abuse of animals for food, clothing, entertainment and experimentation as well as as companions and workers. Right now, there is a new scientific project making its rounds through the media, which is suggesting a new method to keep our cities clean. The idea has been developed by Dutch scientists und is focussing on the utilisation of specific traits of an animals species, which could theoretically help to tackle one of the biggest human evolutionary shortcomings – to be willing to live in harmony with nature and the environment. The project design incorporates a machine and is recruiting and training city crows, who would take care of recklessly discarded cigarette butts.
It is known that cigarettes take between ten and twelve years to decompose. The scale of this waste problem is huge, as it is estimated that every year approximately 4.5 trillion cigarettes are discarded with no regard for the environment. The project is using a so called ‘Crowbar’, which is based on a design created by an American inventor. The device has a large funnel, where cigarette butts can be deposited, and a dispenser for releasing peanuts as a reward. The hope is that crows get busy cleaning up the streets in exchange for some easy food. This idea is trying to utilise the generally acknowledged fact that crows are very intelligent and adaptable being known for their ability to solve complex problems and also to create and use tools.
Before looking at ethical questions related to this idea, there are at least two ‘technical’ problems to address, which the inventors might not have fully thought through. First off all, it is very likely that crows will always have a food choice in our crowded cities, meaning that peanuts may not be that much attractive as a food reward. Secondly, our crows are usually territorial, which means that only one territory holding pair is going to use that machine, which doesn’t seem very efficient, when it comes to cleaning up our large cities. These two problems alone are likely to be sufficient enough, to put this questionable idea to rest.
However, without a doubt, this project raises also several ethical issues, the most important ones being the egocentric and anthropocentric way of human thinking and attitude. Obviously, common sense tells us that the far simpler and cheaper way of solving the cigarette butt problem is to educate people, in this particular case smokers. Instead of constructing, deploying and maintaining machines, which are leaving a noticeable carbon foot print behind, one should rather educate and encourage smokers to quit smoking, or at least to discard their waste products appropriately, which is the least one could expect from a grown up human being.
However, the problem is far more complex than that. Firstly, as mentioned already, the suggested solution is based on an anthropocentric view point. Humans have long tested animals to see how smart they are by seeing if they can do human-like tasks. We are too quick to judge animals by our own human standards, instead of testing within the limits of the animals’ natural behaviour and within their natural setting. By any standard used, we all know that corvids are clever enough to be able to fulfill this particular task, but so are other sentient beings, like toddlers too. And this leads to the second problem.
Humans do not treat sentient and intelligent beings like crows as equals, meaning we treat them differently, and by far not the way we would want to be treated, despite that there is a general agreement about the fact that humans and crows are both, sentient and intelligent. It is actually even worse, the anthropocentric view point is so deeply rooted, that many humans are often tend to focus on the level of animal intelligence (compared to humans) rather than sentience, when it comes to decide how to treat an animal, ignoring completely the fact that humans are not unique in possessing the neurological substrates that generate consciousness.
The truth is that this machine, when it would actually work, would exploit crows, ignoring the fact that it is morally wrong to use or exploit sentient beings in any way. Even worse, this machine is putting these birds at an additional risk by encouraging and rewarding them to handle toxic and also possibly still burning cigarette butts, which might even end up in a place, where we might not want them to be. Furthermore, at least to a certain degree, these birds will be made dependent to rely on human handouts. Based on the natural behaviour of corvids, they will also cache their food, or potential valuables like cigarette butts, as they might want to trade them in later. The result will be that litter will not only be removed, but also be distributed in a different, not nessarily desired pattern. It is also to expect that crows will test the built in scanner to its limits, simply to find out, if other items like pebbles or pieces of paper also trigger food rewards, something which will put the whole machine to a test.
Sadly, even some bird and corvid lovers seem to find this idea fascinating, as they feel that this approach spreads the word and is helping to change and improve the traditionally bad reputation of corvids. It might even do that, but by disregarding the rights of an individual sentient being and by supporting exploitation. Luckily, regardless of all ethical issues, and purely due to technical problems alone, it remains doubtful that this machine is ever going to work.
