We’ve now been in Paris for close to three weeks. It’s a wonderful city, and I’ve enjoyed so many terrific experiences since we arrived: long, sunny walks along the Seine from the Louvre Museum to the Eiffel Tower, terrific concerts by countless street musicians, and many delicious French crepes and baguettes! However, there’s one part of Paris that is slowly pecking away at my enjoyment of the city – Pigeons.
Paris isn’t quite as famous for its pigeons as other large cities like New York and London, but their presence is certainly noticeable – especially if you attempt, as I did, to eat a fresh baguette under the statue of Charlemagne at Notre Dame, an area where the pigeon density rivals that of the tourists. As soon my first breadcrumb dropped, I was surrounded and bombarded by more birds than I could count. This happened again at Tuileries Garden, and yet another time on the Cite Universitaire campus.
Even when I’m not eating baguettes the pigeons seek me out. While relaxing in a small urban park near the Bastille I was lucky enough to receive a pigeon “deposit” on my pant’s leg, followed by another on my chest and a third that landed on my shoulder, narrowly missing my right ear. I can see one such gift being an accident, but three in a row makes me think that these pigeons might have a vendetta against me for the bird research I do back at Emory.
It turns out that I’m not the only one who’s annoyed with Paris’s bird problem. For many years the city has pigeon-proofed historical buildings by placing spikes on all the ledges where the birds might land. Additionally, in 2008 Paris officials set out to curb the pigeon population by building nesting-lofts throughout the city and then sterilizing the eggs while the birds were out feeding (bloomberg). Given my recent experiences, these attempts don’t appear to be working and so I looked into another possible method of population control – feeding the birds poison-laced food.
I was curious about how effective poisoning would be. Do the birds learn to avoid dangerous food? And if so, how quickly does this avoidance behavior develop, especially if that food had a distinct taste or smell associated with it?
How quickly do pigeons learn to avoid poison?
In 1999 a study published in the Archives of Environmental Contamination and Toxicology looked exactly at how quickly pigeons learn to avoid poisonous-food and the effect of hunger on the amount of toxic food they ingested (Pascual et al., 1999).
The study used four groups of eight pigeons. Two of these groups were given as much food as they wanted (ad libitum) for the 6 days leading up to testing while the other two groups were deprived of food. The researchers did two experiments. First they offered seeds laced with the sulfurous-smelling toxin fonofos to one of the ad libitum groups and one of the deprived groups for 6 straight hours. The birds were videotaped throughout the test, and eating behavior was measured by the amount of food eaten as well as the rate at which it was consumed. The second experiment, using the remaining two bird groups, was very similar but the food was offered first for 2 hours followed by a half-hour break, and then for an additional four hours. While not much different then the first experiment, this test showed whether the birds were able to remember that the food was dangerous when exposed to it a second time.
On average, it only took the birds 6 minutes to learn to avoid the food and all of the pigeons from experiment two still avoided the food after a half-hour break. Five of the birds from the food-deprived group did die and the authors attributed this to the fact that these birds ate huge amounts of food in the first six minutes. This is interesting because it suggests that the ability to develop avoidance behaviors is dependent on time, not on the amount of food eaten. Additionally, the video recordings showed reactions (head shaking, food-spitting, vomiting) during the first six minutes, which confirmed that the food was unpleasant to the birds. Given the size of the Parisian pigeons that have harassed me so far, I doubt any of them are food deprived, so unfortunately poisons (or at least poisons that have odor or taste like fonofos) would not be effective.
While this article clearly documented the development of avoidance behaviors and specifically showed that internal state (such as hungry/not hungry) did not affect the rate at which these behaviors we were created, it did not discuss how these behaviors are mediated in the brain.
How is avoidance mediated in the brain?
Most research in avoidance behavior concentrates on the role of a small almond-shaped region in the bottom-middle of the brain called the amygdala, which is thought to mediate avoidance behavior development (Davis, 1992). How exactly it does this is still being debated but the majority of articles suggest that the amygdala helps consolidate a memory associated with an unpleasant experience like eating food that makes you feel sick (Smith et al., 2001). More specifically, some research has shown that it plays a role in the initial acquisition of the memory (Wiliskey et al., 2005). Even though these studies were not done in pigeons, we can use can use them to predict what might have occurred in the pigeon experiment. When the pigeons first ate the fonofos food and experienced the unpleasant side effects, it’s possible that their amygdalae were activated and that a connection between the food and the effects was formed. However, this connection in the brain probably was not strong enough to cause avoidance after just one exposure to the food, so it took multiple exposures over the course of six minutes. Even though the food-deprived pigeons ate more, it’s possible that they didn’t avoid the food any faster than the ad libitum group because their hunger took priority and inhibited the avoidance behaviors from forming (Gilette et al., 1999).
Unless the Parisian pigeons have faulty amygdalae, which I highly doubt, I will unfortunately have to come up with another way to control their population. Perhaps, a poison that doesn’t have any smell or immediate unpleasant effects associated with it? Or maybe the best option is just to take all of my baguette eating indoors. Regardless, it does not appear that I will be poisoning Parisian pigeons anytime in the near future. Now that you’ve finished the post I recommend that you click on the following link and enjoy a 3 minute tune by 1960s comedian Tom Leher, it applies nicely.
– Camden MacDowell
UPDATE: I GOT EVEN WITH THE PIGEONS!
Davis M. (1992) The role of the amygdala in fear and anxiety. Annual Review Neursci 15:353-375
Gillete R., Hatcher N., Huang R., Moroz L. (1999). Cost-benefit analysis potential in feeding behavior of a predatory snail by integration of hunger, taste, and pain. PNAS 97: 3585-3590
Pascual J., Fryday S., Hart A. (1999) Effects of Food Restriction on Food Avoidance and Risk of Acute Poisoning of Captive Feral Pigeons from Fonofos-Treated Seeds. Arch. Environ. Contam. Toxicol. 37: 115-124
Smith DM., Freeman JH., Gabriel M., Monteverde J., Schwartz E. (2001) Lesions in the central nucleus of the amygdala: discriminative avoidance learning, discriminative approach learning, and cingulothalamic training-induced neuronal activity. Neurobiol Learn Mem 76: 403-25
Wilensky A., LeDoux J., Schafe G. (2005) Amygdala Modulates Memory Consolidation of Fear-Motivated Inhibitory Avoidance Learning But Not Classical Fear Conditioning. The Journal of Neurosci 20: 7059-7066