Wednesday, 11 October 2017

Understanding House Crows (Corvus splendens)


Species; Corvus splendens
Malay: Gagak Rumah
Africa: Kunguru
South Africa: Huiskraai
Australia: Ceylon crow, Colombo Crow

Summary of their distribution can be found here;

Description: 16 inches (40 cm) in length, the forehead, crown throat and upper breast are a rich glossy black, whilst the neck and breast are a lighter grey-brown in colour. The wings, tail and legs are black
House crows are omnivorous scavengers which enables them to thrive in association with humans. They are no known house crow populations living independently of humans.

Diet; House crow feed largely on refuse around human habitations, small reptiles, insects, small invertebrates, eggs, nestlings, grain and fruit. They are highly opportunistic and thrive on nearly anything that is edible. They have also been observed to eat sand after feeding on carcasses. We live on a coastal estate and a population of crows living along the waterfront have been seen hovering over the water and bring ashore live small fish. House Crows live fishing has been reported from Singapore; here. My nature photography colleague obtained similar shots of House crows in Penang coming ashore with live fish in their bills.

The following two images were taken by my friend Simon.

House crow with a toad

Crow with a dead Nightjar

Nesting: Crows lay 3 to 5 eggs in a typical stick nest and occasionally there are several nests in the same tree. In South Asia they are parasitized from the Asian Koel. Peak breeding in India as well as Peninsula Malaysia is from April to July.

Female House Crow feeding a Koel chick

Roosting: House crows prefer to roost communally near human habitations and often over busy streets, Studies in Singapore found the preferred roosting sites were in well-lit areas with a lot of human activity, close to food sources and in tall trees with dense crowns that were separated from other trees.

Voice; The voice is a harsh kaaw-kaaw

Group name: murder, horde, storytelling, parcel, muster

Recent cognitive studies are summarised in the following article which is accompanied by a video of some experiments; here 
These experiments employ New Caledonian crows which are at the top of the crow intelligence heap. Other stories of how this species has profound intelligence are plentiful and legendary. The four groups that have the highest brain to body size are humans/primates, dolphins and in the avian world; crows and parrots.
Behavioural biologists have called the crow ‘feathered primates’ because the birds make and use tools, are able to remember large numbers of feeding sites and plan their social behaviour according to what other members of the group do. Scientists in Tubingen located their cognitive ability to activation of the nidopallium caudolaterale, a brain region associated with the highest level of cognition in birds. Crows and primates have different brains, but the cells regulating decision-making are very similar. 

To summarise what smart crows can do;

1.     They can remember your face

2.     They conspire with one another. Crows have been shown to pass on knowledge to other crows by language alone.

3.     Memory Crows passed over a farming town in Chatham, Ontario on a mass route. Being a farming community the crows did some damage with crops. The mayor of the town declared war and several crows were shot. For a number of following years the crows only flew over Chatham at a high altitude and did not stop there.

4.      They use tools and are adept at problem solving (look at the videos of the New Caledonian crows)

5.     They plan. Like squirrels they hide food especially from other crows. They use all sorts of subterfuge to accomplish this.

6.     Adaptive behaviour. Crows pay attention to how the human world works and often use it to their advantage. Some have been observed cracking walnuts by dropping them from the exact height that is needed to bust them open. Others use cars to crack them open and memorise traffic light sequences so it is safer to pick up the food.

Crows generally have a diverse reputation from being wise and foretelling the future to being pests that are hunted. House crows are such a common sight in Asia that they could be easily overlooked if they were not so loud and such poop machines. While they are known as loud and aggressive birds they carry the illustrious scientific name of Corvus spendens. House crows raid rubbish bins, food crops and will enter houses to steal dog food from their bowls. In our housing estate, they were targeted to be shot to reduce numbers but his is a fool’s errand because you are dealing with a very intelligent bird. Shooters were targeting crow populations in the Chinese Gardens in Singapore. The official cars were recognised by the crows on the second visit and they subsequently the area until the danger was over.

When perceived as a nuisance, human being humans resort to trapping and shooting as our main strategies to control or destroy these birds after they have arrived. Whilst satisfying to the zit-faced gun-toters in the crowd, these knee-jerk methods are ineffective because we simultaneously insist on neglecting our rubbish……which is the main reason this species loves us so: we are extraordinarily filthy and wasteful.

House crows are the most successful invasive species within the Corvus genus of birds. Their native homes are found mainly in South Asia, including Sri Lanka, Nepal, India and Bangladesh. They have spread beyond those native regions to more than 20 countries. Although considered a tropical species, they can be found as far away as the Netherlands. If found in Australia they are to be reported immediately to the agricultural authorities.

A recent study by Krzeminska et al from Monash University looked at the DNA samples from house crows from Malaysia and Singapore and smaller samples from Kenya and South Africa to investigate their origins and genetic diversity.
DNA samples were collected from crow’s liver tissue, feathers and blood. The Malaysian samples came from two densely populated areas, Selangor and Penang. Two markers were analysed; nuclear micro-satellite and mitochondrial DNA to make some assumptions on genetic diversity. Another aim was to determine the origins of current crow populations in Malaysia and Singapore.

Samples were taken from Penang, Port Klang and Singapore (as indicated)

The results affirm that house crows in Selangor, Malaysia, may have been introduced form Sri Lanka over 100 years ago. There are records stating that 56 house crows were imported from Sri Lanka to Port Klang in the 1890s. These crows may have been imported to prevent caterpillar plagues and/or reduce human waste.

The crows in Penang and Singapore most likely have been introduced from multiple sources outside of Malaysia. The crows from Singapore may have originated from Bangladesh or its neighbouring countries. The study concluded that house crows could have spread from South Asia over the past 100 years by hitchhiking on ocean-going ships. The house crows of Penang and Singapore had unexpectedly high levels of genetic diversity which makes sense as Penang and Singapore are busy Port cities.

Mobbing behaviour
Mobbing is a defence response to a perceived threat form a predatory bird. House crows have few predators but are aggressive birds that are fiercely territorial. A raptor is seen as a potential threat to the crow, its young and the territory. Mobbing usually involves more that one bird in pursuit of targets....usually birds of prey. Mobbing rarely escalates into physical confrontation which could be damaging to the birds involved. Birds or prey have superior weaponry but crows are ruffians who could inflict damage to a bird that hunts for a living.

House Crow mobbing a Crested Serpent Eagle, Byram, Penang

My experience with House Crows.
Okay they are not the most photogenic bird and I have few images in my collection. We have quite a number of our estate at Seri Tanjung Pinang and local housing committees have decided to shoot them in conjunction with the Penang Rifle Association. A stupid decision on two counts; shooting firearms in a housing estate is fraught with dangers and the crows will always win…….they are smarter than the committees who persecute them.

I have saved a crow struggling from a tree while entangled in fishing line. I have rescued a stunned juvenile who may have been hit by a car. It flew off later that evening. My latest venture started almost 5 weeks ago when tree pruners were chopping down branches in the street behind our home. My wife returning from the supermarket reported two baby birds stunned and injured on the footpath. I recovered both birds and placed them in a glass tank. One was clearly older than the other and the younger one could have had a broken wing. The older one survived the night but its sibling died. I was at a bit of a loss to know what the chick might eat. Being omnivorous it could be anything. It ate a few strands of minced beef.

… I went to the supermarket for inspiration. There I found chicken livers that were soft....and cheap. I cut them into small strands and the surviving chick never looked back. It is like feeding a human baby……….every few hours the demand for food is there. The chick made good progress…it grew noticeably. At night, I would cover the tank. The wings started flapping and the youngster became more alert and demanding. The crow and Coco, our female Toy Poodle, seemed to have their own communication.

We noticed the chick became very active at dusk and would try to get out of the tank. I covered it at night for its own protection but when I left the lid off it would fly briefly to the side of the tank and perch there the night………now indoors, as there are many cats in the neighborhood. The chick was now able to get out of the tank in the morning and hop around outside……..under my supervision. I could not find the chick, on one occasion, for some time until I found a smug-looking cat sitting 3 feet away from the chick which was unharmed by the front door.

I estimated the chick was about 2 weeks old when I found it…..leaving the tank possibly coincided with it fledging…….which is around 28 days from hatching. It would be vulnerable for the next two weeks during which period the parents would continue to feed it.

My next goal was to encourage the chick to fly. Its wings were now well-formed except for a missing primary feather or two on its right wing. It also seemed to have lost a toe in its encounter with the tree butchers.  To this end I did not hand feed the chick but placed food where it could find it on perches. I employed perches of various heights and an upside-down stool with different rung heights. Learning was rapid and after a few days the chick could fly 20-30 feet.

The Crow chick could recognise my voice and my face. since I was the food provider. It did not respond at all to my wife. It would let me pick it up and seemed keen to sit on my arm or shoulder. 

From 4-5 weeks after rescue the crow was free to fly and forage. It would sometimes fly up on the neighbours roof and let me know where it was. By some strange instinct it found out where my study was and seems to know when I am in residence even with wooden venetian blinds hiding my presence. It called for food 3-4 times a day but appeared to eat less. On the 27th night it survived a stormy night perched in the open.

There are many crows along the promenade of our estate and they sometimes dive-bomb Coco. There is no malice in this action and it seems there are always some rascals in a group who will push the boundaries.

 On day 28 post-rescue I estimated this was the time that the crow chicks in the wild would not require their parents feeding them. The fledged  chick was roosting nearby during the night, stopped for some breakfast and then disappeared.  At around 5pm it came down from the neighbours roof and was really hungry. I took my camera out to take a shot and it landed on the camera. When I went inside to get the liver it landed on my back...telling me how hungry it was directly into my ear.
At approximAtely six weeks since hatching it had become a handsome bird.......with a loud voice at meal-times

A video showing the raising of the crow chick can be seen HERE

I have limited House Crow pictures and have taken some from the internet to illustrate various points