Pet Cats And Their Impact On Wildlife

Juvenile green woodpecker

According to the British Trust for Ornithology (BTO) cats kill an estimated 55 million birds in Britain every year and such a predation could be contributing to long-term declines of garden birds. Cats also pose a significant threat to endangered mammals, reptiles and amphibians. Studies have shown that alone the presence of cats in the garden is causing directly and indirectly the death of nestling birds, as parents are disturbed, nestlings are not fed sufficiently and third party predators are invited for a free meal.

Robin fledgling
Robin fledgling

Cats are domesticated animals. They are not a natural predator in our existing ecosystem, as they have been brought in existence by humans. It is estimated that UK households owned approximately 10.3 million cats in 2006, strays not being counted. Trap – Neuter – Release programmes are supported by several charities. However, these programmes are only partly addressing the impact cats have on our wildlife, as most neutered stray cats will be returned to ‘the wild’. With regards to wildlife conservation, it would be more efficient to stop breeding and selling cats completely and to focus on a foster system taking care of the existing cat population, to basically get all feral cats off the road.

Cats and Wildlife – eBook

Birds caught alive and being seemingly uninjured should not be released. Please contact an experienced bird rescue immediately, even if the bird seems to be healthy and uninjured. Due to bacteria (Pasteurella multocida) within a cat’s claws and mouth it is essential that the caught bird is seen and treated with antibiotics straight away. If the bird is left for too long, there is a risk of a fatal infection (septicaemia).

Goldcrest fledgling
Goldcrest fledgling

These are sad but proven facts. Fortunately there are solutions available a responsible cat owner can adopt. So what can be done? The best and safest option for a cat and for wildlife is to keep your cat indoors, or in a sufficient stimulating outdoor enclosure. Cats can also have a good time in the garden in a supervised fashion, or even be trained to be walked on a lead. In other words, the cat flap has to go. Collars fitted with bells or ultrasonic devices are widely recommended, but their effectiveness is questionable. To make them work at all bells need to be changed frequently, as cats are able to learn to adapt their movements to avoid to make any noise. As these collars serve the purpose to make cats more obvious to birds, they may simply provoke even more alarm calls during the nesting period, resulting in a higher nestling mortality as mentioned above.

Blackbird fledgling
Blackbird fledgling

It is also recommended to spread out bird feeders so that feeding flocks might spot a cat more easily. The more birds you attract to your garden, the less likely cats are to catch them as there are more pairs of eyes keeping watch. Chicken wire can be placed around nest boxes and thorny vegetation can be planted to help protect nesting birds. In addition, ultrasonic devices, which are triggered by the cat, can help dissuade cats from using certain areas of a garden. Make sure feeders are not too close to possible cat hiding places. If the lid of a bird box is not secure, the nesting family becomes a target. Check twice when you are siting a nest box. Make sure it is not accessible to cats from a branch or the top of a wall.

Great tit fledgling
Great tit fledgling

One of the things you can also do to keep wildlife safe is to keep your cat at least in at night. Sunset and sunrise are the times of day when cats like to go hunting most. These are also the times your cat is most likely to be run over. That way you do our wildlife and your cat a big favour.

Finding The Optimal Diet For Corvids

Carrion crow Amor

Although corvids are generally known as scavengers and omnivores, the diet of the different corvids species does vary considerably, from species to species, and over the seasons of the year.  Only about 40% of the rooks’ diet for example consists of animal protein, and those being mainly worms, bugs and larvae. They usually don’t eat carrion, as their beak is not designed and able to rip animal carcasses into manageable pieces. The remaining 60% of the rooks’ diet are plant-based products like fruits, seeds and vegetables. During the winter time, carrion crows prefer seeds, berries and carrion, whilst during the summertime they do mainly live on animal protein like snails, worms, insects, small mammals and eggs. 

Carrion crow Amor

Hatchlings And Nestlings Up To 3 Weeks

When raising hatchling corvids it is important to feed a purely insect based diet for the first two weeks of their lives. Ideally these birds should be fed on an insect mash consisting of the following ingredients:

  • Frozen fresh insects like crickets and wax worms
  • Mineral and vitamin mixture like Korvimin ZVT+Reptile (WDT)
  • Boiled egg yolk
  • Soaked NutriBird Bird Complete pellets (Versele-Laga)
  • Minced beef
  • Small amounts of feathers and fur should be added to the mash occasionally, but only when the bird is older than 2 weeks, which will help to produce pellets

Alternatively one can also create a baby food mixture (Modified recipe,  original recipe by Samantha Bedford of Bedfordshire Wildlife Rescue) based on the following ingredients:

  • 2 parts ground up (80%) chicken biscuits (Applaws Kitten Food Chicken)
  • 1 part Hagen Tropicana Breeding Mash
  • 1 part Heath’s Prosecto Insectivorous Soft Food
  • Dried ants, flies and daphnia
  • Korvimin ZVT+Reptile by WDT (Nutrobal for Birds by Vetark)
  • Bene-Bac Powder for Birds and Reptiles by PetAg (AviPro Plus by Vetark)

Carrion crow Amor

Nestlings Older Than 3 Weeks

When the bird turns 3 weeks,  we would start reducing the amount of mash and introduce soaked cat biscuits in addition to the mash fed, which are of an ideal consistency and therefore easy to use for hand feeding. GoCat Chicken and Duck Complete pet food for adult cats (Purina) is well suited for corvids, as it provides the needed high protein contents required. It contains 20% rehydrated meat and animal derivatives, with a minimum 4% chicken and 4% duck (30.0% protein, 10.0% fat content). Tinned dog or cat foods are not a suitable diet for corvids and will most likely cause diarrhoea.

Carrion crow Amor

Fledglings

When the birds have fledged, a broader variety of food items will be added to the daily corvid menu, which will be provided in addition to hand feeding in a dish to encourage self feeding. Food will be supplemented with Korvimin ZVT+Reptile by WDT (Nutrobal for Birds by Vetark) to avoid a calcium deficiency. Alternatively one could also grind thoroughly cleaned empty snail shells, which make a good cheap, natural and easily digestible calcium supplement. The basic diet plan for all corvid species consists of:

  • Soaked cat biscuits (GoCat Chicken and Duck Complete pet food for adult cats (Purina)
  • Minced beef
  • Vegetables (fresh corn or maize, corn on the cob or peas)
  • Fruits (berries, grapes, apple or pear)
  • Scottish Rough Oatcakes
  • Good quality bird food seed mix enriched with peanuts, suet pellets and dried meal worms
  • Live meal worms (larval form of the mealworm beetle – tenebrio molitor) and wax worms (larval form of the wax moth – galleria mellonella)
  • Dead or frozen fresh insects like crickets, calci–worms (larval form of the black soldier fly hermetia illucens) or natural pinkies (larval forms of bottle flies)
  • Hazelnuts or walnuts for jays
  • Occasional food items in particular for crows include dead mice, day old chicks, raw pigeon eggs and cuttle fish bone

Worms and snails must not to be fed to corvids, although being part of their natural diet, as they are carriers of coccidia and worms. Although birds are being encouraged to feed themselves, assisted hand feeding needs to continue until the birds are completely weaned. Fledglings should also be moved into a suitable and spacious aviary, where they can learn to forage and are able to cache food.

 

Top 10 Mistakes Made In Corvid Rescue And Rehabilitation

Carrion crow Chili

During many years of corvid rescue and rehabilitation we came across a number of serious mistakes being made by presumably experienced and unexperienced individuals or rehabbers alike. We would like to share our observations and experiences in the hope that these sometimes fatal mistakes will not be made again, hopefully saving the lives of many corvids in need of help.

Overestimation of one’s own capabilities

Raising an orphaned baby corvid is often seen as easy and very tempting, in particular as the finder is often ‘persuaded’ by the cute and interactive attitude of baby corvids. Lay people, but sometimes even rehabber with some degree of experience with other bird species, ever so often get into the trap of ‘giving it a go’, even when expert help and advice is being at hand. Despite meaning well, it is sadly rather more often about the own ego than the genuine wish to give the bird the best possible second chance he or she deserves. One of the common mistakes being made is that the effort and financial implications needed to raise a corvid are often greatly underestimated, and so are the needs of a sentient being, who is being degraded as an object of experimentation.  Ever so often birds will be inadvertently imprinted on humans and prematurely released by choosing an insufficient release method, the wrong release site or the wrong release time.

Raising corvids as sole individuals without adequate company

Raising a nestling corvid by his or her own will without exception result in some degree of imprinting on humans, the human habitat or pets. However, it would be wrong and one of those mistakes to believe that imprinting is a negative or undesired feature. Imprinting as such is essential for life and survival. But the question is to whom the animal is being imprinted on. Birds are ‘hard-wired’ to many things in their future lives, but they also need to learn the art of feeding, catching prey or social interactions and behaviours from their parents. Songbirds can sing by default, but they do need to ‘learn the tune’ from those around them, those normally being their parents. Imprinting in animals in general can involve more than one sense. It can involve sight, sound and smell.  Furthermore, the imprinting becomes stronger when the animal is under stress, which is in no doubt a survival mechanism. Imprinting is an interaction between instinct and learning. The irreversible and species specific process of imprinting occurs only in a fixed time window. This is the critical period, learning after this period has different weaker effects. To counteract the risk of imprinting, company of a same or similar species bird is crucial, meaning that corvids in particular should never being raised by their own. As many of these young patients are in need of long-term rehabilitation, it is also crucial to understand and to recognise their social needs during the process of maturing, a process which takes many months if not years. One of the mistakes commonly made is that the importance of the help provided by releasable and also unreleasable wild adult birds is underestimated, or not utilised at all, which in fact is an essential tool to teach young birds necessary social skills and behavioural patterns they require for their survival.

Inadequacy of rehabilitation facilities

The fact that corvids should not be raised by their own, the species specific needs and the common requirement for long-term rehabilitation facilities with adequate company, which includes the interaction with unreleasable adult possibly disabled birds, is a challenge in itself, which is often completely ignored or at the very least underestimated. One of the common mistakes being made in this context is that the facilities provided are usually too small and inadequately equipped to be fit for purpose, which is leading often to injuries, chronic diseases like bumble foot or damaged plumage. Corvids are very inquisitive and destructive. The materials to be used in an corvid aviary have to be safe and need to be checked and monitored constantly for wear and tear to eliminate a potential cause of injury.  Although it is possible to combine different corvid species, one should always bear in mind, that the artificially created corvid society is a fragile and dynamic element, which needs constant monitoring and which is subject to frequent and sometimes rapid change at any time. Maturing, pair formation, hierarchical disputes, mood  and hormonal changes during breeding season and moulting are only a few of the causes influencing the stability of a mini flock. CCTV monitoring is an expensive but very useful tool, which allows undisturbed and unbiased observation of behaviour and social interactions between birds, allowing early interference before problems occur.  Sound knowledge and understanding of corvid species specific behaviour is the key, which unfortunately is often completely lacking, being ignored or at least regarded as unimportant.

Underestimation of the importance of hygiene 

The necessity of keeping a larger group of corvids in a confined area for a longer period of time harbours another challenge, which is to maintain a basic hygiene  and cleanliness system. The problem increases exponentially with the number of animals cared for and the good intentions to create a small artificial habitat, which should ideally allow the animals to behave and act naturally. It becomes apparent, when testing corvid patients, that almost all of them are carriers of coccidia and worms. Although it is possible to treat these birds individually, it becomes a bigger problem and challenge when birds are residing in a larger communal aviary, where flock treatment is the only option. It is also impossible and actually not advisable to completely eliminate these diseases, but is seems necessary to keep infection levels as low as possible. Therefore a larger communal aviary will always be a compromise between the ideal case scenario of a species specific nature habitat and a place which can be easily cleaned and maintained to minimise the potential infection risk due to the build up of infected faecal material in areas created for foraging and food caching as well as due to the run off of contaminated material into the surrounding environment creating a potential infection source for wild animals like ground feeding blackbirds or thrushes, but also hedgehogs and rodents.  This is in particular a problem with coccidia,  as the oocysts have resistant cell walls and are discharged unsporulated in the faeces. Oocysts do not survive well at temperatures below -30°C or above +40°C. However, within this temperature range oocysts may survive for more than one year and will sporulate or become infective in as little as 24 hours under optimum conditions in a humid environment between +25ºC and +30ºC.

Raising corvids on an insufficient or suboptimal diet

Although corvids are known to be scavengers and omnivores, the diet of the different corvids species does vary considerably, from species to species and over the seasons of the year.  Only about 40% of the rooks’ diet for example consists of animal protein, and those being mainly worms, bugs and larvae. They usually don’t eat carrion, as their beak is not designed and able to rip animal carcasses into manageable pieces. The remaining 60% of the rooks’ diet are plant-based products like fruits, seeds and vegetables. During the winter time, carrion crows prefer seeds, berries and carrion, whilst during the summertime they also do mainly live on animal protein like snails, worms, insects, small mammals and eggs. These species specific facts should be taken in consideration when creating the menu for corvid patients. Nestling corvids should be primarily fed on an insect or adequate animal protein based diet. However, despite the fact that nestling corvids are being fed snails and worms by their parents, these should not be fed to birds when hand raising them, as internal parasites like coccidia or round worms are likely to be transmitted. Tinned dog or cat food is not suitable either and will lead to severe digestive short and long-term problems. Additional vitamin, mineral and calcium supplements are recommended, as corvids are prone to develop calcium deficiencies resulting in rachitis and feather damage. Pellet producing materials like small pieces of fur or feathers should be mixed under the baby food when older than 2 weeks. When the birds are fledged, the species specific diet preferences become more important and should be accounted for.

Misinterpretation of species specific behaviour as imprinting or tameness

One of the most common mistakes made is the wrong interpretation of normal corvid behaviour, mainly due to lack of knowledge and experience, but also sometimes due to anthropomorphistic reasons. Corvids are highly intelligent, sentient and social animals, who are able to interpret good or bad intentions and behavioural patterns of other animals, humans included. There is a big difference between submissive behaviour in a captive environment and being genuinely tame or imprinted. Young corvid nestling and sometimes even fledglings have not learned yet to regard humans as dangerous entities and will cooperate eagerly when being fed. At that point in time the risk of imprinting is at the highest, but has not necessary happened yet. Adult corvids are also able to adapt very well to a captive situation, in particular when realising that the human caring for them is providing food and is easing the pain. They will remain calm when not being restrained and when a minimum amount of privacy is being allowed, at least as long as they are poorly or compromised due to their injuries. Long-term patients often form a close temporary and person specific bond with their carers, which is being cut when the animal feels ready to go. All these behavioural variations have nothing to do with imprinting or tameness and are simply signs of their amazing ability to adapt to these unique situations. It is important to recognise the difference, as this fundamental ability of a good rehabber will decide over the future and the chances of survival of the animal being cared for.

Underestimation of the importance of species identification and age

Animals are sometimes rescued unnecessary, with good intentions, but without good reason. A young bird alone on low-level branches or on the ground has not necessarily been abandoned, as the young of many bird species will spend a couple of days on the ground before their feather development is complete and they are able to fly. Parents will be close by and come to feed the bird as soon as it is safe. However, to make an informed decision, whether an animal has to be rescued or not, one has to find out what species he or she belongs to and how old the animal is. A healthy rook fledgling on the ground, who is unable to get to higher ground, will not be fed by his or her parents and will require help.  On the other hand, a healthy carrion crow fledgling on the ground, will usually be attended and defended by his or her parents. However, nestlings of any species, found on the ground, will not survive without human intervention. However, the degree of human intervention varies from stepping back and observing the situation, over taking a fledgling out of a danger zone and putting the bird back onto higher ground, to taking the animal in to human care. Species identification and establishment of the correct age are also crucial for the correct choice of release location and time.

Misjudgement of the importance of release area and timing

Hand reared juvenile corvids, but also all long-term patients having been in captivity for longer than 2 or 3 weeks, should always be soft released.  Juvenile corvids are not suitable for release until being 5 or 6 months old, which is usually at the end of the summer after their first partial post-juvenile moult. This allows them to reach full growth and to be able to fly strongly. It also allows enough time to reach enough strength allowing normal competition with other corvids, avoiding excessive bullying. The preferred release time in the U.K. is the end of August and during September. Please also note that an offence may be committed under the Animal Welfare Act 2006, if a released animal does not have a reasonable chance of survival. This may include the release at an unsuitable site, in the wrong territory, when being unfit, or when not having learned to hunt, or when done during the wrong time of the year.

Lack of knowledge of species specific behaviour and ecology

The most common mistake made is the wrong species identification combined with the lack of species specific knowledge. Rooks are breeding in colonies or so called rookeries, as they are very social and gregarious animals. Carrion crows are territorial and have well-defined breeding territories, which are very much fixed but tend to shrink and expand slightly during and outside the nesting season. This means that the territory holding pair is using a single nesting site, which will be defended against any intruders. Sometimes another so called third bird, usually offspring from the previous year, is allowed to stay in the fringes of the occupied territory, helping the territory holder pair to defend their grounds. Non-breeding birds form loose groups, which will reside in an unoccupied area. Outside the breeding season and during wintertime, crows become more sociable and tend to sometimes mix with rooks. When releasing juvenile birds or longterm patients, then soft release is the preferred option. For short-term patients or a hard release scenario, the release site should be chosen very carefully. The location where the bird has been found, might not necessarily be the best place for his or her release. Neither crows nor rooks should be released into an occupied crow territory, in particular not during the breeding season. An area inhabited by a non-breeding flock of crows or rooks would make an ideal place for a release. Soft release works best, when the release aviaries are located in an unoccupied crow territory, near a rookery or communal roost.

Misinterpretation of plumage aberrations and their consequences

Leucism is a general term for the phenotype resulting from defects in pigment cell differentiation or migration. It is a condition in which there is a partial loss of pigmentation resulting in white, pale or patchy colouration of skin, hair, feathers, scales or cuticle, but not the eyes. Leucism can be caused by the reduction of all types of pigment, unlike albininism, which only affects the melanin production. Leucism is occasionally found in corvids, which can show a varying degree of white or pale feathers within an otherwise normal appearing plumage. These abnormal feathers are often more prone to wear and tear and make the bird potentially more conspicuous and prone for predation.

Besides primarily genetic causes, dietary deficiency caused by calcium or folic acid deficiency, or as found in Australian ravens due to a circovirus infection, can also result into this phenotype pattern. It has been also found that agricultural pesticides have a direct impact on reducing food and insect availability. Insects are an essential dietary requirement for almost all bird species, which rely on those for at least a substantial part of the nestling phase of their offspring. Pesticides lead directly and indirectly to the search for alternative and often suboptimal food substitutes and may also result into a progressive weakening of the immune system of adult and young birds, which increases mortality in general, but does more often lead to a varying degree of dietary deficiencies with subsequent plumage and skeletal aberrations.

Recognising the difference between inherited and acquired plumage aberrations is crucial, as acquired plumage problems can be corrected, whilst inherited causes cannot.

Anting Behaviour Observed In Crows

Carrion crow Pepper

Our routine aviary cleaning procedures also involve the cleaning of drinking and bathing facilities of our crows. This is usually seen with great anticipation by all our corvids. Birds in general, but in particular corvids, are very clean birds, and can’t wait to make use of a refreshing bath. We frequently add natural apple cider vinegar to bath and drinking water, which keeps the water longer fresh and has positive health properties for the birds.

The video shows carrion crow Emma taking advantage of a bath in natural apple cider vinegar, before we have been actually able to add drinking water to dilute the vinegar further. This behaviour can be seen as the equivalent to or a variation of anting, frequently observed in the wild.

Anting can take on different forms. Some birds will pick up ants in their beaks and rub them over their feathers, while others will open their wings, lie down and allow ants to penetrate their plumage. Birds seem to prefer using ants that produce formic acid. Formic acid is being used by ants as a defense mechanism.

One theory on anting is that the formic acid could act as a fungicide, bactericide and insect repellent, while others think that it is the vitamin D content in the acid that birds are interested in. However, birds sometimes use alternative anting tools, such as millipedes and fruit, and in our case apple cider vinegar. Some scientists believe that anting is used to preen feathers and helps to prevent the drying out of the plumage. Another suggestion is that anting has an intoxicating effect on birds, as some birds have been seen to shake themselves and seemingly lose control over their ability to walk.

Carrion Crow Emma Anting

The Amazing Recovery Of Carrion Crow Pan Tau

Carrion crow Pan Tau

Pan Tau, a juvenile carrion crow, came to us for rehabilitation via a veterinary surgery, where the kind finder, who rescued and cared for the bird for more than a week, has brought Pan Tau to seek professional help. The veterinary surgeon actually already suggested to put Pan Tau to sleep, but the finder insisted to give him another chance. This is where we got involved and agreed to take over the care of Pan Tau.

Carrion crow Pan Tau

Pan Tau has been found unconsciously on the road after being hit by a car. He suffered a severe spinal injury, which resulted in a paralysis of wings and legs. Luckily, Pan Tau didn’t suffer fractures or other internal injuries. However, the spinal injury or spinal contusion resulted in his inability to stand, sit, walk or fly. We treated him accordingly and never stopped being amazed and encouraged by his trust and determination.

Pan Tau’s Determination Was The Key To Success

Although there was no breakthrough after a fortnight, Pan Tau did show some subtle improvements, which persuaded us to continue with treatment including an intensified form of physiotherapy. About four weeks after the accident his balance problems started to improve and he was able to sit by himself on his hock joints. The spasms in his feet also started to resolve. Another four weeks later he was able to stand and started to walk and even perched the first time, still having coordination and balance problems.

After about three months of intensive care and rehabilitation Pan Tau could be moved into an outdoor aviary, where he enjoyed the new freedom, independence and interaction. Pan Tau will not be releasable, as he has got still some neurological, mainly balance issues and his flying skills are not good enough. He is meanwhile a fully integrated, well accepted and indepedent member of our residential crow family.

Carrion crow Pan Tau

The recovery of Pan Tau, despite all odds and scientific predictions, is an amazing story in itself. We remain fascinated by his personality, his determination and his ever surprising ways to show us how much he is enjoying life, which is his way to say thank you for being giving this chance.