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September 10, 2014
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Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.
Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.
Foot deformities are ubiquitous in urban pigeons – why? As you’ll know if you’ve spent any time watching the pigeons of towns and cities, something like one in every ten (or more) has missing or partial toes, or swollen toes, or other pedal deformities of some sort. And then there are really extreme individuals – the ones that are missing feet altogether. Here’s a sorry bird I photographed at Kew, London, the other day…
Poor footless urban pigeon, encountered close to Kew train station. The right foot is completely absent; the left one had at least one toe, curled round such that the bird was walking on the toe's lateral side. Photo by Darren Naish.
I’m talking here about the domestic form of Columba livia, the so-called Rock pigeon or Rock dove. And, while I’ve only noticed deformed pigeons here in the UK, it certainly isn’t a UK-only thing, as continental European and North American [UPDATE: and South American] people will confirm.
The bird in the photos here was able to fly around and feed itself, and it might be broadly described as ‘healthy’. However, note that it’s in pretty poor condition. The feathers on its head and neck looked terrible and its rectrices (the big tail feathers) were frayed and shabby. I reckon this is partly due to an inability to groom and scratch itself: obviously, birds use their feet to reach parts that they can’t get to with the bill.
Composite image showing preening pigeon and feather lice. Image by Dale H. Clayton and Sarah E. Bush, University of Utah.
The impact of this is more than cosmetic, since birds with a poorly maintained or unrepaired plumage are disadvantaged in flight relative to tidier individuals, and less able to keep themselves warm and waterproofed. And a bird that isn’t able to groom parts of its plumage is also at risk of being unable to keep on top of parasites like ticks and feather mites (see the ‘pigeon’s eye view’ Tet Zoo article linked to below). And, as has been demonstrated through various experiments, birds with shabby-looking plumage are less attractive as mates (Clayton 1990), so a bad-looking pigeon is likely to be a non-breeding pigeon. It’s also worth noting that (like many animals), pigeons preferentially use one foot more than the other as goes the way they land and perch and sit and so on (Fisher 1957), so individuals that lose or damage their preferred foot might end up being doubly disadvantaged (imagine being right-handed, and then having to rely only on your left hand for evermore). I don’t know how concerned people are about the emotional well-being of animals like urban pigeons (or how far they’re prepared to go in admitting that non-human animals have feelings and states of mind), but I think we can be fairly confident that the most severely deformed of these birds are – at least at times – miserable, unhappy and frustrated.
Near-footless pigeon again. Another question about these birds: would they be able to survive if they weren't making a living by picking up scraps in urban environments? Photo by Darren Naish.
Several ideas have been put forward to explain the many foot problems seen in urban pigeons. Some probably lose toes after getting them tangled in litter or anti-pigeon netting, or after they’ve injuries received from anti-pigeon spikes installed on signs and ledges. Fine wire, string, cotton thread and even human hair can all cause problems for birds when caught on or around digits, and some people say that interaction with fine thread and string and so on is the primary cause of pigeon foot damage. It’s also sometimes suggested that the deformities result from infections received after standing on excrement, and also that the birds become damaged through interaction with chemicals used on roofs and building stone. But the ‘chemical injury’ idea is unlikely to be correct, since (A) exactly what sort of chemicals are we talking about here, and why have they been used on buildings in the first place?, and (B) a chemical would basically have to be a powerful acid or alkaline agent (hydrochloric acid, or a very strong bleach) before it might damage a bird’s feet. For completeness, note that hereditary deformities like those reported for some captive populations of other pigeon species (Flach & Cooper 1991) might also explain some of the abnormalities observed in urban pigeons.
Other hazards that might affect an urban pigeon. At left: voracious park-dwelling pelicans! (photo: PA). At right: deceased Wood pigeon (Columba palumbus) following encounter with motor vehicle; note 'terror-moulted' lack of rectrices. Photo by Darren Naish.
Pigeons are not, of course, the only birds that end up with damaged feet. You might recall the foot-lacking Rock pipit Anthus petrosus I featured here recently…
I’ve been photographing pigeons a lot lately, but pigeons of a different species from C. livia. More about that another time. For previous Tet Zoo articles relevant to some of the subjects covered here, see…
Refs – -
Clayton, D. H. 1990. Mate choice in experimentally parasitized rock doves: lousy males lose. American Zoologist 30, 251-262.
Fisher, H. I. 1957. Footedness in domestic pigeons. The Wilson Bulletin 69, 170-177.
Flach, E. J. & Cooper, J. E. 1991. Clinical and pathological findings in two Mauritian pink pigeons (Columba mayeri). Veterinary Record 129, 48-51.
About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.
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Feral pigeons lacking toes or even the entire foot are also very common in Spanish cities, and entangling with any sort of strings seems to be the main cause. But I wonder why this problem doesn’t seem to affect urban wood pigeons and collared doves (at least, I’ve never seen any individual of these species affected). Perhaps because these latter are more arboreal, and they don’t spend so much time walking on the ground or roosting in buildings.
Link to thisAppart from difficulted preening, flight feathers of limb injured pigeons suffer because the birds use them as a prop when walking.
I’d heard it suggested it might be that the toes were frozen off after they perched on cold metal during the winter. That wouldn’t work if it also occurs in hotter countries though.
Link to thisI’ve seen plenty of sparrows (Passer domesticus) missing a foot, too. I don’t think there’s anything special about pigeons in this regard except that they’re usually more common than other birds, so we’re more likely to notice.
Link to thisI would guess its less a matter of urban pigeons suffering more injuries than other birds, but rather of being more likely to survive with severe injuries. Cities don’t just have easily accessed food, as you mentioned, they also have low predator densities.
Gruesome injuries are very common in turtles too, which I think is not due to their being injury-prone, but to not being particularly more vulnerable to predation just because they lack a limb or two.
Link to thisI always wondered about that, I’ve only noticed birds with these problems in larger cities. In Paris while resting at an old opera house almost all the pidgeons I saw there were missing toes or entire feet, it looked like they had infections and such it was really gross. I noticed a couple of grackles at the San Fransisco airport who were the same way, only less infected and more just complete lack of a foot.
Back home I’ve seen maybe one in thousands of grackles over the course of years with a foot/toe problem. The only difference I can think of is there aren’t as many anti-bird measures here as there are in place like the airport, or places like Paris that have lots of historical architecture.
Link to thisI always thought the scaly leg mite (Knemidokoptes), a common parasite of chickens, was the cause of foot deformities in pigeons.
Link to thisWait- a pelican eating a pigeon?!?
Link to thisI’ve seen many footless pigeons in New York City. It’s so sad-they can survive on litter and scraps, but, well, it would be like living without hands, I guess. And they aren’t picked off by predators because there aren’t enough in cities. The world’s ecology is so messed up.
Foot lesions like the ones you described are also very common in urban pigeons here in Portugal. Although tangled material can cause foot necrosis and loss of digits, I believe that viral diseases, like Papilomavirus and specially, Avipoxvirus (Avian Pox), are major causes for this conditions. They usually affect the bare parts of the body (you can find some birds also with skin lesions on the eyelids, cere and beak) and are transmitted by direct contact (Avian pox can be also transmitted by mosquito bites).
Since some viral strains are very host-specific, that might explain why, in the same urban area, we see Columba livia with lesions but Streptopelia decaoto and Columba palumbus apparently healthy.
Link to thisFoot deformities are reasonably common in pigeons in Auckland, New Zealand too; as are leg damage or foot loss in Red-Billed gulls.
It never gets really cold here so sub freezing temperatures aren’t the reason.
And I haven’t seen anti pigeon spikes on buildings here.
Starlings and blackbirds occasionally have leg damage leaving their foot bent back or the leg splayed out to the side but I haven’t seen any lacking feet.
I cannot recollect having seen Dominican (Black Backed) gulls or Malaysian Speckled Doves with foot damage.
So the foot damage seems to vary with the species.
I wonder if some species are more likely to sustain damage to their legs or are just better at surviving it.
At least one of the starlings which had it’s leg splayed out to the side when on the ground still had glossy iridescent plumage so it must have been able to groom itself somehow.
LeeB.
Link to thisI’ve observed feral pigeons in Blackpool with withered feet and missing toes, still with litter attached to their lower legs and feet, such as synthetic threads.
Link to thisI have a similar observation to LeeB in Sydney, Australia. I have noticed more injured pigeons in Sydney than in Wollongong a smaller city to the south. I have also noticed a fair few Silver Gulls with damaged feet eeking out a living in the urban environment.
Link to thisFilipe, I’ve forgotten, unforgivable missing, Avian Pox as a major cause of foot lesions in feral pigeons. Yes, it’s very common. Curiously, Avian Pox virus cause much milder lesions in raptors, it’s fairly frequent in a variety of birds of prey, and highly contagious, but normally it courses with cutaneous papillomas that eventually fall and heal without consequences.
Link to thisI think the cause of the high occurrence of foot injuries in feral pigeons are a combination of high pigeon densities in big cities, favouring Pox contagion, abundance of tangling garbage, and anti pigeon spikes.
Very common in Vienna, too.
Link to thisFoot deformities are fairly common in urban Great-tailed Grackles, at least in Texas. Usually I see damaged or missing toes or permanently curled toes (rather like a club foot). I have also seen a number of Laughing Gulls with missing or partially missing feet.
Interestingly I can’t immediately think of seeing missing feet in House Sparrows or Starlings… perhaps I don’t notice the injuries because their feet are smaller and harder to see.
The most obvious foot problems I’ve seen in non-urban species are bumblefoot and related diseases in sparrows and House Finches. I have also caught a few Carolina and Black-capped Chickadees with missing toes, badly-healed broken toes, and in one case an entire missing foot, but they all managed to survive well enough to breed (I was catching pairs at their nests for a project).
Link to thisI’ve seen both urban pigeons and brewer’s blackbirds with missing toes, as well as with grossly deformed feet. I always figured it was a combination of injury, infection, and enough food and predator suppression that an injured bird wouldn’t die rapidly. Interestingly, I see the injured birds around the market, but not around nearby townhomes, where a cooper’s hawk often hunts.
Link to thisHere in Hawai’i it is the australian zebra doves (Geopelia striata) that are most commonly seen with foot deformities. Avian pox is one of the main culprits. It is an oft-retold tale of the challenges concerning the native avifauna here in the islands.
Link to this