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.

 

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.

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 though, 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.

An Impressive Encounter Of Cultural Learning In Corvids

Juvenile crow sitting on the fence

Animal culture describes the current theory of cultural learning in non-human animals through socially transmitted behaviours. This involves the social transmittance of a novel behavior, both among peers and between generations of the species concerned.

About six years ago I have been called for help as a fledgling crow has flown into a window in one of the enclosed courtyards of the hospital. When I arrived I found a concussed carrion crow fledgling being cold and wet. The bird also showed nutritional deficiencies and subsequently a poor plumage with many white primaries and secondaries. All these problems made it necessary to take the fledgling bird into our care to treat the immediate concussion issues but also to keep the bird for at least one year to allow a full moult into a new healthy plumage, which only happens once a year. Whilst assessing and securing the crow fledgling I have been closely watched and scolded at by the crow parents, and by another crow sitting in some distance on a roof.

Playing and interacting crows

Crows are territorial birds. The hospital grounds are forming the centre of the crow territory occupied by the pair of crows, whose fledgling I have been asked to rescue. As documened in the literature, the third crow is likely to be a male crow, who has been accepted by the territory holder pair to reside in the outskirts of the occupied territory helping them to defend their home. One year later I have been called again to rescue another crow fledgling which got stuck in an open hospital sewer canal. The poor bird was soaking wet and hypothermic and had to be taken into care as well. As the year before, the parents watched the incident and tried to defend their youngster.

Corvids Never Forget A Face

Ever since the first incident five years ago, as soon as I enter the hospital grounds to go to my work place, these three crows including their offspring will raise the alarm and at least one of the crows will accompany me until I enter one of the buildings and disappear from their sight. Interestingly, it does not matter what clothing I am wearing, they will easily identify me and recognise my face. Even youngsters born the years after the last incident will raise the alarm and join in, as soon as they become independent and are able to fly and follow me. The members of this extended crow family are also able to identify me when I stand seemingly at random behind one of the hospital windows watching them whilst they are doing their daily business.

Adult carrion crow sitting on the fence

This encounter, which demonstrates nicely cultural learning, shows clearly that information regarded as essential and worth keeping is communicated between family members, related and unrelated birds, even years after the actual incident. This lets us conclude that long living animals like crows have some sort of cultural heritage, which is being passed on to future generations. As it is also known that territorial carrion crows will also visit communal roosts, there is also the possibility to consider that some of this or other more essential and useful information of this cultural heritage will also be passed on even further.

Wildlife Rescue – A Privilege To Interact With Sentient Beings

Rook Teal'c in our outdoor release aviary.

The encounter I am writing about repeats itself often, but every time it is a completely new and unique event. We are getting a new rescue bird patient in and are treating the animal until he or she is ready for release back into the wild. Again and again we are astonished about how quickly we are able to establish a close relationship with the bird in our care. It is always the same ingredients it needs to gain each others trust: Respect, patience, understanding and love. This brief story is dedicated to all of our rescue birds, but in particular to Teal’c, a very close rook friend, who came into our care after we found him soaked, cold and orphaned sitting in a puddle on a busy main road on the Isle of Wight.

Teal'c is an orphaned rook fledgling, who recovered well after being found orphaned with signs of severe dehydration and starvation.
Rook Teal’c

Teal’c was very poorly when we took him in, and we actually didn’t believe that we would be able to save him. But Teal’c survived, grew up very quickly and made friends with all family members, but in particular with Kerstin and myself. His curiosity and urge to explore new unknown things was astonishing. Nothing would escape his notice. Everything had to be thoroughly checked and explored, which would eventually include ‘scientific’ tests like soaking and testing the impact of gravitational forces on objects of interest.

Communication Between Species

Teal’c was also very communicative, having used his language, but also beak, wings and feet to make sure his message has been understood correctly. It did always amaze us, when Teal’c was looking into our eyes and beyond, deep into our souls, as this was exactly how it felt like. He was ever so gentle, the way he communicated, showing the whole range of emotions a human could possibly show.

When he was young, it seemed that he had occasional nightmares, not being happy at all to be left alone. He had to be brought to bed, or his perch in the aviary. Gentle talking and stroking would calm him down. When he was sitting on our shoulder, then he would press his body, neck and head onto our body, until he was about to fall asleep. On the other hand, if he would not get the attention he wanted, then he would voice his disappointment and even get the odd tantrum, which also could include some gentle, well chosen, but surely noticeable physical enforcement of his desires.

Rook Teal'c is growing up quickly into an inquisitive juvenile bird.
Rook Teal’c

There are hundreds of situations and unique encounters we have had with Teal’c, but also with a variety of other bird species, all providing unequivocal proof of the highly developed intelligence and emotional life of birds in general and corvids in particular.

Time To Say Good Bye

Teal’c grew into a beautiful young Rook, far to quickly the time was passing by. He once managed to escape rather by accident then by will, but came back, as it was not the right time to depart. Late in September we eventually released the juvenile rook friends Sam, O’Neill and Teal’c. They went off together joining a local mixed corvid bachelor group. Before the three birds where about to depart, we looked again into each others eyes, and we all realised, our hearts heavy and filled with sadness, it was now the right time to let go. We knew, that we will never forget each other and that our unique bond will persist, despite us being physically separated and living our own lives.

Rook Teal'c after being released sitting in a tree and paying his previous home a visit.
Rook Teal’c

All three birds are occasionally visiting our garden, and their past temporarily home, whilst passing through on their way from the roosting trees to the fields. All three birds will start calling and interacting with us and old bird friends. But they will keep their distance, as it should be. Now they are free, back into the wild, where they belong to.