Certain species of animals associate particularly with humans, usually for the food inadvertently supplied by an affluent and wasteful primate.
Commensalism (https://en.wikipedia.org/wiki/Commensalism) implies habituation. This is because the association implies proximity.
To see the house sparrow (https://www.inaturalist.org/taxa/13858-Passer-domesticus), pecking crumbs close to a table in an outdoor cafe, surprises nobody who understands that this species is exclusively commensal, never living in the wild (https://en.wikipedia.org/wiki/House_sparrow).
However, some commensal species remain unhabituated, instead remaining as shy of humans as fully wild animals would be. They live among us - indeed, in some situations exclusively among us - but they never get used to us enough to trust us any more than wild animals do.
And this vigilance, apprehensiveness, and distrust may continue, generation after generation, even where humans pay no attention to the animal in question, do nothing deliberately to harm it, and indeed hold it in kind regard.
Such a species is Spilopelia chinensis (https://www.inaturalist.org/taxa/1455918-Spilopelia-chinensis), at least in the urban/suburban environment of Perth, Western Australia, where I live.
This species is common in suburban streetscapes, where its peaceful cooing (https://www.youtube.com/watch?v=WEHe6W_D4lo and https://xeno-canto.org/species/Spilopelia-chinensis and https://avocet.integrativebiology.natsci.msu.edu/recordings/5987 and https://search.macaulaylibrary.org/catalog?taxonCode=spodov&mediaType=audio&sort=rating_rank_desc#_ga=2.93916062.2047640190.1660101380-673334876.1658548323 and https://ebird.org/species/spodov) is a familiar sound, disliked by nobody, and a reminder of the inoffensiveness associated with doves.
Most persons in Australia, including naturalists, take S. chinensis for granted in a neutral or positive way.
However, when one thinks about it, there is something odd in its relationship with us.
Spilopelia chinensis forages exclusively on the ground. It habitually flees from approach at the same distances that any wild, terrestrially foraging columbid would, if approached in some remote area of grassland or savanna. This behaviour seems stereotyped, instinctive, and unaffected by experience.
Australia has a rich indigenous fauna of Columbidae (https://www.inaturalist.org/observations?place_id=6744&taxon_id=2715&view=species).
However, the most successful spp. of columbids in Australian built-up areas are introduced deliberately from elsewhere.
These are:
Playing a minor role in the metropolitan area of Perth are two indigenous species.
Phaps chalcoptera (https://www.youtube.com/watch?v=v8x07ONuZb8 and https://www.inaturalist.org/taxa/3335-Phaps-chalcoptera) was indigenous to what is now the Perth Metropolitan area, before Europeans arrived about 1820.
It has been marginalised by settlement, remaining only in peripheral, densely wooded suburbs. Here it remains shy of humans, and tends to be detected more by its hooting call (https://ebird.org/species/combro1?siteLanguage=en_AU and https://xeno-canto.org/species/Phaps-chalcoptera) than by being actually seen.
Ocyphaps lophotes (https://www.inaturalist.org/taxa/3681-Ocyphaps-lophotes) is similar in body size and diet to S. chinensis. It was indigenous only to the dry interior when Europeans arrived. It has benefited from agriculture, becoming common in the farmed countryside where wheat is grown.
And, like several other ecologically similar indigenous birds, it has tended to expand its range, towards relatively rainy, formerly well-wooded regions, now altered by the human species (https://absa.asn.au/wp-content/uploads/2021/03/Cor-Vol-35-Pg73-81-Created-Pigeons.pdf and https://birdlife.org.au/bird-profile/crested-pigeon).
Ocyphaps lophotes has recently begun to encroach on the Perth metropolitan area, where it seems to be increasing in the southern suburbs. I have lived in this metropolitan area since 1977, but the first time I spotted O. lophotes in the suburbs was in 2019.
However, the indigenous O. lophotes has yet to usurp most of the suburban habitat of the introduced S. chinensis. The former tends to occur in parks, rather than the streetscapes continually exploited by the latter.
And, significantly, O. lophotes already has achieved a level of habituation not seen in S. chinensis.
This is surprising, because S. chinensis
The anomaly, then, is that that S. chinensis, a species somewhat co-evolved with humans from the start, actively promoted by humans in the sense of being deliberately introduced, and universally tolerated - if not liked - by the current human population, shows no sign of treating its human benefactors as anything other than potential predators.
How can we explain this anomaly?
In contrast to the failure of S. chinensis to habituate, various birds, indigenous to Australia, have become so habituated that they can be approached closely in suburbs and streetscapes, and even voluntarily approach one to within 1 metre.
Prime examples are Rhipidura leucophrys (https://www.inaturalist.org/taxa/8143-Rhipidura-leucophrys), Gymnorhina tibicen (https://www.inaturalist.org/taxa/8575-Gymnorhina-tibicen), and Grallina cyanoleuca (https://www.inaturalist.org/taxa/8583-Grallina-cyanoleuca).
This lack of shyness is in line with faunas of islands, and is consistent with the relatively small incidence of indigenous predators in the fauna of Australia - the island continent.
So, here is a hypothesis:
Spilopelia chinensis originates in a part of Asia where there is a minimal ethic of conservation. Instead, the cultural norms are such that animals are a resource for consumption by humans. It has long been the custom, in the farmlands of China, to harvest any edible animal, from invertebrates through amphibians and fishes, to birds and rodents.
At the same time, it is the nature of columbids that they are among the less intelligent of birds. They rely not on an ability to learn, but mainly on a combination of fecundity and explosive flight, for their survival.
Because of risks of predation to S. chinensis in its original, anthropogenic habitat, natural selection has 'hardwired' into it an instinctive pattern of wariness and flightiness, in which proximity to people is avoided.
Because S. chinensis has minimal cognitive versatility, the instinctive pattern of anti-predator behaviour has tended to remain unmodified. And this has applied even after generation after generation of actual experience, in a situation free of predation by the human species, should have taught the bird that it can relax around people.
What we thus find, in the Australian suburbs, is a species with an odd combination of characteristics. Spilopelia chinensis is one of the least approachable species of birds encountered in the metropolitan area: unhabituated even where it is the commonest 'feral' species present.
And this suggests that, eventually, we may be left with the following ironic situation in Perth.
If the indigenous, and not particularly shy, O. lophotes continues to adapt to the suburban environment, as it has been doing in recent decades, then it may eventually replace, and marginalise, S. chinensis on the basis of competition for food.
And, to the extent that this happens, it may transpire that S. chinensis will have come and gone from many Australian streets, its remarkable degree of caution proving to be ultimately futile - and perhaps self-sabotaging - in an adaptive sense.
Comentarios
https://www.bassendean.wa.gov.au/council-meetings/bassendean-river-parks-management-committee-meeting/bassendean-river-parks-management-committee-meeting/184/documents/brpmc-2017-05-03-att2.pdf
In contrast to Streptopelia chinensis, the Australian species, Ocyphaps lophotes, has shown little potential as an introduced species.
Ocyphaps lophotes was introduced to New Zealand, Europe, and the USA, including Hawaii (see page 231 of https://books.google.com.au/books/about/Introduced_Birds_of_the_World.html?id=fssQAQAAMAAJ&redir_esc=y and https://catalogue.nla.gov.au/Record/174442).
It failed in all of these locations.
Streptopelia chinensis has been introduced to not only Australia, but also Hawaii, California, Mauritius, New Zealand, New Caledonia, New Britain, Sulawesi, the Moluccas, and Fiji.
It has succeeded in all these areas. This means that S. chinensis occurs in the suburbs of not only the various Australian cities, but also Los Angeles and Auckland.
Reference: pages 220-222 in https://books.google.com.au/books/about/Introduced_Birds_of_the_World.html?id=fssQAQAAMAAJ&redir_esc=y and https://catalogue.nla.gov.au/Record/174442.
@jeanshelton @paul_contreras @bbunny
Dear observers of Streptopelia chinensis in Los Angeles, do you - like me here in an Australian city - find that this species remains shy and wary of people, not allowing close approach?
@jeremygilmore
In my suburb in Western Australia, the normal 'flight-threshold' of Streptopelia chinensis is about 10 m. What this means is that, as one walks about in the streets, or goes out from the house into one's garden, any encountered individual(s) of this species of columbid are so wary and lacking in trust that they generally fly off when one is still no closer than 10 m away.
I know of no other terrestrially-foraging bird in the metropolitan environment that shows such 'wildness', which seems fully in line with what it would be in a bird living in a predator-rich environment with no habituation. This is puzzling, because a) this species has a long history of association with humans, and b) there is categorically no persecution of it by humans in this metropolitan area.
My question to you is: in Cape Town, where Streptopelia capicola is indigenous, what would you estimate the 'flight-threshold' to be in its case?
Hmm, it's not something I've ever given much thought. It would have to be directed at a more bird-oriented person or @tonyrebelo
I hardly know the Cape Turtle Dove. We have Redeye and Laughing Doves in our area. Their flight distances vary if you have a dog or if you feed them. And if they are on the ground or in a tree or on a roof. But generally in the region of 5-10m if one approaches casually. But I have never measured it or tried to vary it. One usually encounters them closer in gardens, but they fly off as one arrives. One does not generally encounter them on the ground in urban parkland unless someone is feeding them.
@tonyrebelo
Many thanks for your valuable observations.
Streptopelia senegalensis, introduced to Western Australia, is fairly common in the Perth Metropolitan area. Here, it behaves similarly to what you have described, and I do not find it to be anomalously apprehensive.
Streptopelia semitorquata seems, over the last few decades, to have replaced S. capicola in the suburbs of the southwestern Cape of South Africa. I suspect that S. capicola was fairly common in the suburbs of Cape Town during my boyhood, in the 'sixties (see map in http://thebdi.org/2022/03/08/cape-turtle-dove-streptopelia-capicola/).
Streptopelia semitorquata is not really comparable with S. chinensis, because it is partly arboreal in its foraging.
So, I realise that the comparison I have requested is difficult to make.
In order to understand the context:
Several of the terrestrially-foraging birds in metropolitan Australia allow remarkably close approach by humans.
The most striking example in my garden is Grallina cyanoleuca (https://www.inaturalist.org/taxa/8583-Grallina-cyanoleuca), which is so trusting that I would find its behaviour surprising even for a deliberately fed bird. In reality it needs no particular encouragement to approach me as closely as one metre, in my garden.
Other good examples are Rhipidura leucophrys (https://www.inaturalist.org/taxa/8143-Rhipidura-leucophrys), Chenonetta jubata (https://www.inaturalist.org/taxa/7176-Chenonetta-jubata), Eolophus roseicapilla (https://www.inaturalist.org/taxa/144560-Eolophus-roseicapilla), and Cacatua tenuirostris (https://www.inaturalist.org/taxa/116839-Cacatua-tenuirostris).
However, the phenomenon is most striking in cases where there is a close relative in Africa. The local form of Porphyrio (https://www.inaturalist.org/taxa/418530-Porphyrio-melanotus) forages out in the open on lawns in a way seldom seen for its congener in South Africa (https://www.inaturalist.org/taxa/474333-Porphyrio-madagascariensis).
The following is a frequent scene in my local suburban park: https://www.inaturalist.org/observations/66240760.
Given this 'Galapagos-like' tameness on the part of certain birds in Perth, I find it surprising that a species so thoroughly associated with humanity as Streptopelia chinensis is more wild, and less trusting, than any comparable indigenous bird, in the suburbs.
https://onlinelibrary.wiley.com/doi/10.1111/j.1472-4642.2010.00741.x
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