do siblings mate ?

[rossy]

heres one for you all, its something ive been thinking about, we know that some birds pair off year after year, and with the help of ringing birds, we can monitor their lifespan etc, but is it known that siblings actually breed as a pair , one way of knowing like ive put the ringing ie red, year 1 , blue year2, also by their numbers and so forth, so when birds that migrate and the resident ones are ready, you should be able to see if this is the case, personally i think this happens, does anyone know for sure ? and is their records of this interbreeding ? rossy.

[faz]

as a general rule no birds do not not inter breed as this would weaken the blood line not saying it dose not happen sometimes in the main no

[Wrenna]

Inbreeding in a wild population of any animal tends to only happen when there is a shortage of that species in the area. I think the inference with birds is that once a bird fledges, matures, and is ready to breed it has moved sufficiently far enough away from it's siblings and parents that the chance of it choosing a relative as a mate is quite small.

I remember reading an article not too long ago about Crows in a suburb of New York, where there was a greater prevalence of disease amongst it's crow population. Research showed that there was a high percentage of incestuous matings.
I will see if I can dig out said article.

[Wrenna]

This is not the same article that I read, but discusses the same study:

Cornell Chronicle: Inbred crows more disease prone

[Dogghound]

Although it may happen im sure it is greatly reduced as Wrenna says by dispersal of young. It is often more complex than this as different species have different rates of dispersal.

[thebeard]

as populations become more fragmented and restricted, inbreeding starts to become more prevalent, slowly causing a reduction in fitness and ultimately the decline of the population.

most animals try and avoid it though!!!

[RKB]

Originally Posted by thebeard

slowly causing a reduction in fitness and ultimately the decline of the population.

This is mostly theoretical. If you think of the Chatham Island Robin or the Nene, then the population went down to just a couple of birds, yet there are now hundreds of closely related birds and they seem ok.

I've been ringing a population of tits for years, and monitoring all the breeding pairs. They have short dispersal distances, so I know that if they are not in my study area then they are dead. Of about 300 pairings, I've only had one that contained birds from the same nest. The fragmented habitat and short dispersal distacnes means that it's going to happen from tiem to time, and many of the other pairings involve cousins, grandsons etc.

But it's not as simple as looking at birds from the same nest. Extra-pair copulations are quite common, even among very monogamous species. For up to 30% of chicks in many popaultions, daddy isn't their daddy (interestingly, I've read that this figure is consistently around 15% in Western human societies, including ours).

So, even if you have two birds from the same nest airing together, they are not necessarily full siblings. As some species 'egg dump' (females lay eggs in other nests, like a Cuckoo, but they're reared with the rest of the brood), they may not be related at all.

Finally, spatial autocorrelation means that birds in one area are always going to be more closely related than birds from another area. I don't think anyone has shown that siblings actually avoid recognise and avoid each other. But dispersal of juveniles is not even - females consistently go further than males, so the sexes tend to separate themselves, and this might be an innate strategy to avoid in-breeding.

[poschiavanus]

The problem of inbreeding occurs when a population is large enough to sustain quite a number of nasty genes. When closely-related individuals in such populations mate the nasty genes get exposed.

BUT if inbreeding carries on over many generations then the bad genes are eliminated and inbreeding ceases to be a problem. This is what happens in island races and species. These have tiny founder populations (perhaps one gravid female), and also has occurred with animal breeds created by man (whether as pets, food, or in the lab).

[faz]

so in short no it dose not happen

[thebeard]

in short.. it does!