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Variability in House Sparrows, or could I have breeding female Spanish Sparrow [NW UK] (1 Viewer)

Jane Turner

Well-known member
On Apr 25th this year we caught a female Sparrow with a fully developed [in use] brood patch so it was quickly processed. The ringer pointed out that it looked a bit odd - and so I looked and indeed it was - in fact had I not been in NW UK, but in place where Spanish Sparrow was a possibility, it ticked several boxes for that species. Not wanting to hold a bird on eggs any longer than necessary, we took a couple of photographs and measured the bill, which was in the overlap zone at the very top end of House Sp. We let her go and we joked about how easy it would be to overlook a vagrant female Spanish Sparrow and wondered about what the offspring might look like.

Today I found out!

So my question - has anyone seen a House Sparrow with a fore-supercilium like these two birds? The newly fledged juv seems to also have an unusually uniform and warm toned crown. Their bills are pretty impressive too!
 

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Jane Turner

Well-known member
Wing length of the female 77mm, bill to skull 16.5mm, depth at feathering 9.0mm, latter both at the extreme upper limit for House Sparrow

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tconzemi

Tom
Supporter
Europe
Just thinking out loud: bill size of much studied Galapagos finches changes within one generation as a response to drought, why not in House Sparrows? These bills really look huge
 

JWN Andrewes

Poor Judge of Pasta.
The male Spanish Sparrow up in Cumbria back in the '90s, he hung around over a year didn't he? Were there any hybrids seen in the area afterwards? Not much direct bearing on your birds Jane, but a potential precedent.
 

Jane Turner

Well-known member
The male Spanish Sparrow up in Cumbria back in the '90s, he hung around over a year didn't he? Were there any hybrids seen in the area afterwards? Not much direct bearing on your birds Jane, but a potential precedent.
I don't know. If does beg the question that if that juv does come out the other side of its post juv moult with a load of Spanish Sparrow characters - i.e an F1 hybrid, does that mean that the female can be assumed to be a bona fide one!
 

qwerty5

Well-known member
United States
Just thinking out loud: bill size of much studied Galapagos finches changes within one generation as a response to drought, why not in House Sparrows? These bills really look huge
If House Sparrows were subjected to large bill size variation like Galapagos finches then I think it would be well documented, given their widespread range, across all different habitats. My guess from my limited knowledge of genetics is that House Sparrows don't have genetic material for large bills, while Galapagos finches do. I would say that House Sparrows lost the genes for bill variability long ago because it wasn't needed, while the finches retain all the genes because it helps them adapt. Just my 2 cents. As I said I have a limited knowledge of all this, so it may all be bullcrap
 

THE_FERN

Well-known member
If House Sparrows were subjected to large bill size variation like Galapagos finches then I think it would be well documented, given their widespread range, across all different habitats. My guess from my limited knowledge of genetics is that House Sparrows don't have genetic material for large bills, while Galapagos finches do. I would say that House Sparrows lost the genes for bill variability long ago because it wasn't needed, while the finches retain all the genes because it helps them adapt. Just my 2 cents. As I said I have a limited knowledge of all this, so it may all be bullcrap
It's pretty certain there is genetic variation for bill size. Here's why: the above discussion shows the various house and related sparrows differ in bill size. They frequently hybridise. So even if there were strong selection for a particular narrow bill size in house sparrows, constant hybridisation would bring genes for different bill sizes back in. In fact, I'm sure it's a labile character given the catholic nature of house sparrows' diets.
 

qwerty5

Well-known member
United States
It's pretty certain there is genetic variation for bill size. Here's why: the above discussion shows the various house and related sparrows differ in bill size. They frequently hybridise. So even if there were strong selection for a particular narrow bill size in house sparrows, constant hybridisation would bring genes for different bill sizes back in. In fact, I'm sure it's a labile character given the catholic nature of house sparrows' diets.
I agree that with hybridization there is variation, but I was saying that I didn't think that much was present within a pure P. domesticus. Because if that much variation was present in domesticus, I would assume it would be documented. So I was saying that I didn't think that the large bill was present solely from variation within domesticus, but was probably from hispaniolensis at some point. Again, I'm definitely no where near an expert on this.
 

qwerty5

Well-known member
United States
My point is that I think it would be documented if there was that much variation in pure domesticus, so I think the photographed bird probably has hispaniolensis genes from relatively recent hybridization, if it's not a full Spanish Sparrow.
 

Jane Turner

Well-known member
I have something of a needle in a haystack problem - 50+ sparrows in the garden, 7-8 ringed, yet I have ringed 250 since this time last year!

Reading up it seems that call might be of some use
 

Jane Turner

Well-known member
Well I have caught another sibling - and this one dropped a couple of feathers while I was taking photos. Similar large bill - its still growing and is 0.3mm under the max allowable for House, it has a well-marked fore-super, much stronger chin patch than its same age House Sp friends, odd black feathers outside the range a breeding plumage let alone a juv still growing its 1st gen flight heathers should have. Its crown isn't all chestnut like the other juv I caught however - but it does have well-marked mantle lines.
 

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ZEISS. Discover the fascinating world of birds, and win a birding trip to Columbia
ZEISS. Discover the fascinating world of birds, and win a birding trip to Colombia
ZEISS. Discover the fascinating world of birds, and win a birding trip to Colombia

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