This image by Colleen Goh a.k.a. damselfly shows a single crow mobbing a White-bellied Sea Eagle (Haliaeetus leucogaster).

Crows are notorious in their boldness. They have been known to dive-bomb dangerous predator like hawks, eagles, kites, owls and even people. Screaming loudly, a few will mob a potential predator, taking turns striking it with force.

See our earlier posts on: harassing kites, attacking a kite and mobbing predator birds.

This post is a cooperative effort between NaturePixels.org and BESG to bring the study of bird behaviour through photography to a wider audience.

The Asian Koel (Eudynamys scolopacea) is a cuckoo, and like many cuckoos, it is a brood parasite. The female koel lays her eggs in the nest of one or more species of hosts, allowing the latter to incubate her eggs and feed her chicks until they are fledged and for some time after. In Singapore it has always been assumed that the Asian Koel’s host is the House Crow (Corvus splendens). Evidence that this was so only came in the mid-2000s (Wee, 2005).

The drama started in October 2003 when a pair of House Crows nested in one of my two ceram palm (Rhopaloblaste ceramica) growing in my garden. The outcome of this nesting was an Asian Koel.

Three months later, there was another nesting and again, a keol fledged from the nest. A third nesting was detected, again three months from the second. And yet again, no crows fledged. This time three koels fledged, the second a week after the first and the third, three days after the second.

I expected another nesting in July 2004, three months after the last nesting. Unfortunately the nest was ripped apart and the debris landed on my driveway. What caused this destruction was not known.

One month after this, an egg was found smashed on my driveway. Apparently a new nest had been rebuilt in the crown of the palm. On September 2004, two other eggs were found smashed below the palm.

After this incident, the crows did not return to nest.

I have always been puzzled by the above events, especially the destruction of the nest and eggs. The publications that I managed to read all say that Asian Koel does not eject the host egg or chick. The book by Davies (2000) specifically states that Asian Koel is among six cuckoos that do not eject the host eggs or young.

Then I came across the book by Payne (2005) where it cites Baker (1934): “The Koel may remove a host egg.” Apparently the koel’s shorter incubation of 13-14 days compared to the crow’s 16-20 days allows the former to hatch first and thus eject the eggs or nestling of the host. On the other hand there have also been cases of the koel nestling growing up together with those of the host. Payne (2005) also reports that two or more cuckoos sometimes fledge from a nest.

So it is very possible that the eggs that landed on my driveway in July 2004 could be the egg of the crow, pushed out by the koel chick.

However, a number of questions remain unanswered. Which bird was responsible for ripping up the nest in July 2004? What happened to the koel chick if, indeed, it did eject the crow egg in August 2004? Could the two eggs that were ejected in September 2004 belong to the crow? Did the crows abandon the nest after this, leaving the koel chick to its fate?

Unfortunately, birders in Singapore have never been interested in such observations and the few ornithologists around have other research priorities. However, a new breed of bird photographers is actively documenting bird behaviour that one day may provide answers.

Tang Hung Bun is one of them. In December 2005 he documented the contents of a crow’s nest that had a naked chick and an egg (top left). The next day when he checked the nest, he found only the egg, the chick was gone. Two weeks later, he checked and to his surprise found three eggs (top right).

Unfortunately, before he could complete his observations, the local Town Council people destroyed the nest. Part of our crow eradication programme.

Could the naked chick be a crow? Could it be subsequently removed by a koel? Did the koel return to lay one or more eggs? More questions to be answered!

Images by Tang Hung Bun.

References:
1. Baker, E.C.S. (1934). The nidification of birds of the Indian Empire, vol. 3. London: Taylor & Francis.
2. Davies, N. B. (2000). Cuckoos, cowbirds and other cheats. London: T&AD Poyser.
3. Payne, R.B. (2005). The cuckoos. Oxford University Press.
4. Wee, Y.C. (2005) Look, what came out of the crow’s nests. Nature Watch 13(1):22-25.

“I have an observation about crows which was unusual to me. In 2006, I saw flocks of crows surrounding a fisherman at a canal in Pasir Ris, near the Avana Downtown East Resort. The fisherman was using a casting net to catch tilapia in the shallow canal. He threw away many small silver fishes about 2 inches long. I observed a crow with a fish in its beak, flying to a grassy area. Instead of eating the fish, the crow found a patch on the ground and buried the fish, as if to hide it from other crows. It then flew off to get some more. Can someone explain this behaviour? Thanks.”

Crows have been reported to store food when there is more than they can consume (Feher-Elston, 2005). They will hide or cache the excess food in tree crevices or dig a hole in the ground, dropping the food and covering the hole with leaves. They usually remember where they cache it and return later when needed.

Marzluff & Angell (2005) reported smaller corvids collecting hard-shelled pine and hazel seeds, store them in their throat pouch and fly long distances to their caching grounds. This happened during summer and the seeds were retrieved in winter. American Crows (Corvus brachyrhynchos) have been known to cache a variety of animals too large to finish at one time.

So far, caching has been reported for western crows and ravens. There are no reports of caching among local crows. This is the first report, unless someone can point me to an earlier report.

References:
1. Feher-Elston, C., 2005. Ravensong: A natural and fabulous history of ravens and crows. Jeremy P. Tarcher/Penguin, New York. 208 pp.
2. Marzluff, J. M. & T. Angell, 2005. In the company of crows and ravens. Yale University Press, New Haven & London. 384 pp.

The House Crow (Corvus splendens) is a rather aggressive bird (above). At slightly more than 40 cm from the tip of the bill to the end of the tail, this bird is up to 30% larger than the Black-shouldered Kite (Elanus caeruleus). The crow moves in small flocks whereas the kite is usually found singly or in pairs during nesting periods. Only outside the breeding season does the kite feeds and roosts communally. Thus in any confrontation between these two birds, the kite invariably ends up the loser. This is especially so during nesting when the kite is vulnerable to attacks by crows.

Allan Teo is one photographer-birder who has noticed the aggressiveness of the crows. In November 2006 he wrote in saying: “I observed many times that the poor Black-shouldered Kite is always getting harassed by House Crows and many raptors.“ Allan observed a single House Crow harassing the three juvenile kites (above). When one of the kites flew above and hovered around the crow, baring its talons in the process, the latter simply ignored it. Allan also witnessed adult kites being harassed, possibly by Changable Hawk Eagle (Spizaetus cirrhatus) - that may well be juvenile Brahminy Kite (Haliastur indus) (above). Thankfully the attack was only a mock one that concluded with only nerves ruffled. There was another case of these kites being harassed by marsh harriers. He has also seen images of the Steppe Eagles (Aquila nipalensis) that appeared some months ago around the Changi reclaimed areas attacking the nest of the Black-shouldered Kites. In this case the kites managed to chase off the eagles.

Tang Hung Bun reported seeing House Crows harassing White-bellied Sea Eagles (Haliaeetus leucogaster) in Malacca in March 2006. He managed to capture the action on video with the sea eagles rolling their bodies in flight and occasionally managing to turn the table on the crows, chasing them off in the process (1 and 2).

Input by Allan Teo and Tang Hung Bun. Images by Allan except House Crow by Tang.

Crows are omnivorous. This means that they eat anything and everything, from grain, fruits, flower nectar, insects, eggs and birdlings, small mammals and what have you. They are scavengers, thriving where there are scraps of food available. That is why they are so successful around urban areas.

We have posted accounts of crows attacking and eating a rat and a bat. We also have an account of a White-bellied Sea Eagle (Haliaeetus leucogaster) catching a rat swimming in the sea off Changi. But this is the first time we have an account of a House Crow (Corvus splendens) actually fishing.

Meng and Melinda Chan witnessed a House Crow in Punggol last year quietly standing on a rock by the sea. Suddenly it dived into the water and emerged with a fish. With the fish firmly in its bill, it bashed it against the rock until it was stunned or probably dead. Then it started ripping it apart and eating it piece by piece. It was then about 7.00 pm in the evening and the light was low, so the image they managed to capture was not as bright and crisp as they would like it to be.

For the records, there have been reports of House Crows picking fish from shallow water or even plunging into deeper water to fish.

Input and image by Meng and Melinda Chan. Thanks to Kok Hui we have the correct ID of the bird in the above image.

Reference: Madge, S. & Burn, H. (1994). Crows and jays. London: Christopher Helm.