# Most numerous species of mammal? Bird? Reptile? **URL:** \ **Category:** Factual Questions\ **Created:** [July 27, 2011, 4:06pm UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499 "2011-07-27T16:06:27Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![StarvingButStrong](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/starvingbutstrong/32/335_2.png) [@StarvingButStrong](https://boards.straightdope.com/u/StarvingButStrong)\ **Post date:** [July 27, 2011, 4:06pm UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/1 "2011-07-27T16:06:27Z")
Question is due to idle chitchat over a meal. Which species of (X) has the most living creatures on earth? We mostly settled on rats and pigeons (due to their association with humans) and garter snakes (mostly just because we’d all seen them everywhere we’d lived.) Any better guesses? Or even \ authoritative answers? ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [July 27, 2011, 5:21pm UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/2 "2011-07-27T17:21:18Z")
According to many sources, the most numerous species of bird is the Red-billed Quelea. > **[Red-billed quelea](https://en.wikipedia.org/wiki/Red-billed_Quelea)** > > The red-billed quelea (/ˈkwiːliə/; Quelea quelea), also known as the red-billed weaver or red-billed dioch, is a small—approximately 12 cm (4.7 in) long and weighing 15–26 g (0.53–0.92 oz)—migratory, sparrow-like bird of the weaver family, Ploceidae, native to Sub-Saharan Africa. > It was named by Linnaeus in 1758, who considered it a bunting, but Ludwig Reichenbach assigned it in 1850 to the new genus Quelea. Three subspecies are recognised, with Quelea quelea quelea occurring roughly from Se... ---
**Author:** ![Giles](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/giles/32/60_2.png) [@Giles](https://boards.straightdope.com/u/Giles)\ **Post date:** [July 27, 2011, 5:28pm UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/3 "2011-07-27T17:28:12Z")
> [@engineer\_comp\_geek](#): > > According to many sources, the most numerous species of bird is the Red-billed Quelea. > [Red-billed quelea - Wikipedia](http://en.wikipedia.org/wiki/Red-billed_Quelea) No, they are beaten by the [chicken](http://en.wikipedia.org/wiki/Chicken) (worldwide population about 24 billion). There would be very few mammal species that beat _Homo sapiens_’ 7 billion. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [July 27, 2011, 5:39pm UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/4 "2011-07-27T17:39:21Z")
> [@StarvingButStrong](#): > > We mostly settled on rats and pigeons (due to their association with humans) Pigeons are widespread, but not very abundant. Even a large city probably only has a few thousand birds these days, and at their peak maybe a few hundreds of thousands. In the wild a single flock of Quelea numbers in the tens of millions, and until just 50 years ago they outnumbered humanity. Even the common house sparrow would outnumber pigeons by orders of magnitude, and there are approximately 3 chickens for every human in the world right now. Pigeons just ain’t in the running for most abundant bird. I’m not sure whether sparrows or chickens would be the most abundant, but my hunch would be sparrows. Similarly, while rats are widespread, they aren’t very abundant. For every brown rat in the world there are something like 40 house mice. However getting reliable estimates of rodent numbers is difficult because populations fluctuate so fast. Australia is notorious for rodent plagues, both native species and house mice, and a single event may comprise billions of animals, which are all dead a few months later. So the most abundant rodent on Earth today may not be the same species as tomorrow. > [@](#): > > and garter snakes (mostly just because we’d all seen them everywhere we’d lived.) Any reptile species from temperate regions would be highly unlikely to be the most abundant, simply because it is a temperate species. As with rodents, populations are going to fluctuate wildly. At the height of the hatching season, the populations of many species will be hundreds of times higher than during the rest of the year. The most sensible place to look would be for a tropical species that is widely naturalised around the world. My bet would by the house gecko. Pretty much every building in the tropical and sub-tropical world is home to at least half a dozen, giving them a population in the tens if not hundreds of billions. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [July 27, 2011, 5:42pm UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/5 "2011-07-27T17:42:46Z")
> [@Giles](#): > > No, they are beaten by the [chicken](http://en.wikipedia.org/wiki/Chicken) (worldwide population about 24 billion). Interesting. I wonder if a lot of sources don’t count the chicken because its population is artificially high (we breed them for food). > [@Giles](#): > > There would be very few mammal species that beat _Homo sapiens_’ 7 billion. I poked around on the net for a bit, and it seems that rats and mice are both pretty close to humans. Some estimates put rats slightly above humans, but the most authoritative source I found (the world health organization) had humans in the lead, though not by much. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [July 27, 2011, 6:03pm UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/6 "2011-07-27T18:03:22Z")
IIRC, there are many more bacteria in even a healthy person than the number of all the vertebrates on the planet. I’d prefer to explore the question based on total mass of the individuals of a species, rather than the number of individuals. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 27, 2011, 9:09pm UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/7 "2011-07-27T21:09:31Z")
> [@](#): > > IIRC, there are many more bacteria in even a healthy person than the number of all the vertebrates on the planet. Yes, but those bacteria come in myriad different species. And the Wikipedia page on the quelea claims that they’re the most abundant _wild_ bird species, so the claim is not in conflict with chickens. **Blake** , sparrows are certainly abundant in North America, but how broad is the geographic range of the most abundant species? ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [July 27, 2011, 9:21pm UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/8 "2011-07-27T21:21:34Z")
> [@engineer\_comp\_geek](#): > > Interesting. I wonder if a lot of sources don’t count the chicken because its population is artificially high (we breed them for food). Everybody knows that you shouldn’t count yer chickens. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [July 27, 2011, 10:21pm UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/9 "2011-07-27T22:21:49Z")
> [@Chronos](#): > > > [@](#): > > > > IIRC, there are many more bacteria in even a healthy person than the number of all the vertebrates on the planet. > > Yes, but those bacteria come in myriad different species. Misleading. I’m not going to spend a lot of time Googling this, but [optimallivingfoods.com/my-bacteria.html](http://optimallivingfoods.com/my-bacteria.html) shows > [@](#): > > There are 500 different species of bacteria that live in and on you that total about 100 trillion bacteria. If the 500 populations were equal (they’re not!) that would still be 200 billion bacteria per species in an average human. All off-topic of course. I was just presenting an extreme example of why I think total biomass is a better indicator of a species’ size than number of individuals. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [July 28, 2011, 12:46am UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/10 "2011-07-28T00:46:46Z")
> [@Chronos](#): > > **Blake** , sparrows are certainly abundant in North America, but how broad is the geographic range of the most abundant species? [Huge](http://en.wikipedia.org/wiki/File:PasserDomesticusDistribution.png). As in substantial portions of all continents. This is why I’m inclined to give the edge to sparrows over chickens. While chickens are widely farmed, most chicken facilities will be supporting an equivalent number of sparrows on the spilled feed. Large flocks of wild sparrows also exist in cities alongside pigeons, however unlike pigeons, which are mostly restricted to inner-city urban areas, they are also common in suburban and semi-rural parts of the city as well as natural forests and woodlands. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [July 28, 2011, 12:49am UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/11 "2011-07-28T00:49:29Z")
> [@septimus](#): > > All off-topic of course. I was just presenting an extreme example of why I think total biomass is a better indicator of a species’ size than number of individuals. I think the question that must be asked is “better for what?” Biomass might be the best measure for issues, but numbers of individuals for other issues. For example, if you’re measuring the likelihood of extinction, individuals are more important than biomass. Individuals are a better (though not perfect) measure for biodiversity as well. If we’re talking long-term survival of a species, 10 whales is not as healthy a population as 10 million birds, even if they weigh the same. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [July 28, 2011, 1:04am UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/12 "2011-07-28T01:04:09Z")
> [@septimus](#): > > I’d prefer to explore the question based on total mass of the individuals of a species, rather than the number of individuals. Then you should probably start you own thread, because that’s not what the Op wants in this thread. To highlight how much difference this makes: 1 billion cattle at ~200kg each = 200 billion kilos of beef. 7 billion mice at ~20g each = 1/10th of a billion kg of Chinese takeaway. ---
**Author:** ![Suburban\_Plankton](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/suburban_plankton/32/219_2.png) [@Suburban\_Plankton](https://boards.straightdope.com/u/Suburban_Plankton)\ **Post date:** [July 28, 2011, 1:34am UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/13 "2011-07-28T01:34:27Z")
> [@njtt](#): > > Everybody knows that you shouldn’t count yer chickens. Nah, it’s OK. We’re only counting the ones that have already hatched. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [July 28, 2011, 1:47am UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/14 "2011-07-28T01:47:54Z")
> [@Blake](#): > > [Huge](http://en.wikipedia.org/wiki/File:PasserDomesticusDistribution.png). As in substantial portions of all continents. This is why I’m inclined to give the edge to sparrows over chickens. While chickens are widely farmed, most chicken facilities will be supporting an equivalent number of sparrows on the spilled feed. Large flocks of wild sparrows also exist in cities alongside pigeons, however unlike pigeons, which are mostly restricted to inner-city urban areas, they are also common in suburban and semi-rural parts of the city as well as natural forests and woodlands. I don’t believe the House Sparrow is really in the running vs domestic chickens. Although it has a wide naturalized range, it’s not all that common in most of it. In North America they aren’t found significantly in forest or woodland. In Latin America they are quite scarce in parts of the indicated range (e.g. they exist in Panama but I wouldn’t put the national population at over a few thousand, and that’s mainly restricted to urban areas; I can’t recall ever seeing one at a chicken farm.). They have been declining in the UK; I’m not sure of their status in the rest of Europe. It’s nearly absent in China and southeast Asia, and even where it occurs in Africa it is mostly confined to cities by related competitors that occupy wilder areas. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 28, 2011, 4:24am UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/15 "2011-07-28T04:24:29Z")
Huh, I knew that there were sparrows all over the place, but I hadn’t realized that was all the same species. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [July 28, 2011, 4:50am UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/16 "2011-07-28T04:50:55Z")
> [@Chronos](#): > > Huh, I knew that there were sparrows all over the place, but I hadn’t realized that was all the same species. There are lots of species that are called sparrows, but not all of them are in the same family. The bird we are talking about is the [House Sparrow](http://en.wikipedia.org/wiki/House_Sparrow), _Passer domesticus_, introduced into North America from England (and once known here as the “English Sparrow”) which is in the family Passeridae. The native North American birds known as sparrows are in the family Emberizidae (buntings). ---
**Author:** ![mac\_bolan00](https://avatars.discourse-cdn.com/v4/letter/m/b3f665/32.png) [@mac\_bolan00](https://boards.straightdope.com/u/mac_bolan00)\ **Post date:** [July 28, 2011, 10:22am UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/17 "2011-07-28T10:22:26Z")
domestication and farming messed up the contest. i’d like an estimate of the most numerous, say, before 5,000 bc. but staying at the present, what’s more numerous, sparrows or african quilas? ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [July 28, 2011, 11:41am UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/18 "2011-07-28T11:41:15Z")
> [@septimus](#): > > I’d prefer to explore the question based on total mass of the individuals of a species, rather than the number of individuals. It’s estimated that 25% of all land animals on earth, by mass, are ants. ---
**Author:** ![BDoors](https://avatars.discourse-cdn.com/v4/letter/b/e95f7d/32.png) [@BDoors](https://boards.straightdope.com/u/BDoors)\ **Post date:** [July 28, 2011, 11:53am UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/19 "2011-07-28T11:53:58Z")
> [@Alessan](#): > > It’s estimated that 25% of all land animals on earth, by mass, are ants. Many different species, though. Largest single species by biomass is probably Antarctic krill, or maybe domestic cattle or _homo sapiens sapiens_. ---
**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\ **Post date:** [July 28, 2011, 12:03pm UTC](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499/20 "2011-07-28T12:03:59Z")
If we’re talking about the past, would passenger pigeons be in the running? [Next page](https://boards.straightdope.com/t/most-numerous-species-of-mammal-bird-reptile/590499.md?page=2)