Hybrids

[RobinP]

Is it only Ducks, Geese and Gulls that hybridize? You never hear of, say, a Blue/Great Tit hybrid or a Song/Mistle thrush do you? Is it something in the water?

[Dogghound]

Carrion crows and hooded crows hybridize too.

[epops]

what i find odd is mallards crossing with egyptian geese dunno why but it seems an unlikley pairing

[Picidae]

testing: having problems posting on this thread, says page can't be found!

interesting question but I suspect one that can be answered by looking at: a) species distribution, b) barriers of respective reproductive genes (ie. compatibility/incompatibility between reproductive DNA) and c) natural selection (ie. that favours positive mating between same species since hybridised offspring are less fit than parents on the whole).

[Picidae]

Whether or not a species will hybridise, may well depend, firstly on genetical differences, secondly on where it is geographically, and thirdly, how it came to be in a local area in the first place. Finally, where a population of a species is in very serious decline, you may well get evolution of reproductive systems to 'allow' hybridisation with other species, but whether this would be fast enough to respond to the pressures causing that decline is another matter (eg. climate change, habitat destruction, geological changes etc)

[aeshna5]

In captivity quite a few groups of birds are regularly hybridised such as falconers' hawks or falcons; finch crosses (mules), pheasant crosses + no doubt others.

I haven't heard of a Blue x Great Tit, though they are less closely related than previously thought as all the British tits other than Great Tit have recently placed in different genera. However where their ranges overlap in northern Europe, Blue x Azure Tit hybrids are not infrequent, indicating a relatively recent divergence.

[Picidae]

The causes of species separation and hybridisation are complicated but from the little I know: In localised geographical areas where normal populations of two different species come into contact on their natural range, there's less chance of hybridisation, since their reproductive systems are strong enough to make hybridisation non-productive - ie. thus, through natural selection, hybridisation does not occur, or if it does, offspring are not produced.

[Picidae]

apologies all my posts are supposed to be in one post but it's not happening!

Reproductive systems (and hence specie barrier can also be made weak by evolution and new species can emerge from hybridisation.) You get clinal areas though, and here, in highly localised populations, hybridisation is common and where an endemic subspecies can eventually emerge if hybrids are fitter (or as fit) as the parental species on the edges of that geographical clinal range. You also get hybridisation where the geographical barriers that separate two species have been removed (eg. through artificial introduction, captive birds escaping, vagrancy etc) and will hybridise with other species belonging to the normal population distribution for that local area as a consequence of having little or no contact with it's parental species . (Here, there is less chance of fit offspring/or any at all in some species, in others, one parental species is fitter than the other and the dominant parental species can cause great conservation concerns for the weaker species).

[Hobjob]

Pheasants and capers do it

Some shore birds too - stilt and avocet in USA

Parrots and macaws too, though if in the wild I'm not sure.

I remember talk of a long straying eurasion oystercatcher
being amorous with an African oystercatch in South Africa
but I don't know outcome.

[RobinP]

There is a record of a Dunlin - Purple Sandpiper cross in the UK, must have been quite a sight.