Crow he went a-fishing

by Matthew Cobb

This hooded crow in a park in Ramat-Gan (near Tel Aviv) appears to use bread to catch a fish.

This video was first posted in 2000 by Dr Oren Hasson, and has just popped up on Imgur and Tw*tter. You can read Dr Hasson’s description of the behaviour here. Hasson gives some references to previous observations of bait fishing in herons in Japan and Florida. I presume it was the kind of behaviour shown in these two videos:

This heron in a Mauritius park is using a cigarette butt in the same way.

This heron (location unknown) is trying a similar thing with some bread, but it takes a while before it gets it right (maybe it’s a young bird?)

http://www.youtube.com/watch?v=uBuPiC3ArL8

So what did birds use before bread and cigarette ends? Here’s Dr Hasson’s thoughts about how ‘his’ crow began fishing. He’s also particular sharp in the third paragraph, where he ponts out that the bird is giving up something it can eat (bread) in order to get something else (a fish) which is presumably of higher value.

In addition to this particular pool, there is a large artificial pond in the park, in which there are many fish. Fishermen regularly arrive to this pond to fish. Little egrets, night herons, pied kingfishers, kingfishers, and white-throated kingfishers are among the common fish-eating birds that hunt fish in it, and there are a number of places that could be used by crows as a perch to catch fish. So there was a chance that this behavior was practiced by many crows, depending, perhaps, on how long ago was it first learnt. To test this, I spread slices of bread all over the park to see how crows handle them. The result was that crows do what crows do, namely, they ate all pieces of bread on the spot. It was only near that particular small pool that I have seen this phenomenon again. As this was at the beginning of the crows breeding season, and as there were two nests that were built at the time on two adjacent sycamore trees next to the pool, I suspected, by following these unmarked crows, that there was only a single crow, possibly two (one of each nest), which are using the bait-fishing technique. One way or another, it was a rare phenomenon.

Altogether, my own bait, slices of bread spread around the pool, worked well. I have seen about 10 crows’ attempts to use bread bait to lure fish, all on the very same perch, and 4 of them were successful. I managed to document two of them, one with my 200 mm camera (photos on the top-left corner), the other with a very good digital video camera recorder that I rented for this purpose. Given my equipment, and given that the crow was not tame enough to fish when I was at the edge of the pool, the only way I could do this was by leaving my camcorder continuously recording on a tripod, while watching the pool from a distance. The two wmv files that I put here, are the result of this low-tech effort. One shows an unsuccessful attempt, the other a successful one, pretty much like the first time I saw the crows doing it. Observations were made during March, 2000, except for the time I videotaped it, which was on April 5th, 2000.

Crows of Caledonia are known to prepare sticks and adjust their size, or bend metal hooks for hunting larvae in wood. Ravens are known to pool fishermen’s bait out of the water, and steal their fish. Crows all over the world are known to lift up pecan nuts and drop them on the road to crack and eat them. They are also known for using this technique to break clams on rocks. However, giving up bread in order to gain fish is unique, mostly because the crow gives up some resource it owns (food), not just expending energy. Admittedly, it retrieves most of the bread and eats it before it gets lost. Admittedly, it may not understand the fish will eat the bread. But clearly, it did not need to soften the fresh bread that I put their just a while ago, and it lost some of it in the water. In the end, when it catch the fish, it does not hesitate leaving the bread behind, to fall in the water. Did it expect to eventually lose its bread when it brought it to the pool (rather than just expected to gain a fish)? – This is really difficult to tell. However, as much as can be seen, this was a deliberate behavior, and very special. Regarding whether it qualifies for the definition of tool-using, maybe it does. It took a slice of bread, held it in its foot, and put only pieces of it in the water. As shown in the video, it seems as though it even deliberately adjusts size and rate of the crumbs it dropped in the water, according to the presence or absence of fish in the water next to its perch. However, more data should have been gathered to determine that.

There are other birds known to use bait to lure fish, the most famous among which is the green-backed heron, which drops insects in the water. In those birds the trait is known to be heritable, being improved later by experience. In the hooded crow it is much more likely to be a self learnt behavior by one individual, maybe copied by another, than a rare lucky mutation.