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Steve
Thursday 18th September 2003, 21:21
So your migrants like your swallow martins etc pop up to the uk for the summer, I have had some in the old barns around me, as far as I know they had two sets of young, the last lot flying around for the first time at the begining of sept. So off they go back to the south for spring /summer, presuming they bump into birds that dont migrate and that are nest building,do they breed again when they get there? do any birds breed at both ends of a migration?

CJW
Thursday 18th September 2003, 21:34
No.

Andy Bright
Thursday 18th September 2003, 21:41
Originally posted by CJW
No.

What's the betting that someone is going to come up with an obscure example proving it did happen once? I can hear certain individuals looking through reference books as I type 3:-)

Steve
Thursday 18th September 2003, 21:42
I know differently, which is why I asked the question!!

CJW
Thursday 18th September 2003, 21:43
Originally posted by Andy Bright
What's the betting that someone is going to come up with an obscure example proving it did happen once? I can hear certain individuals looking through reference books as I type 3:-)

I can't imagine who you mean, Andy!

HH75
Thursday 18th September 2003, 21:59
Hi all,
I know that European Bee-eaters now breed in South Africa,where the species was formerly only a non-breeding visitor during the southern summer,but I think that these aren't birds that had already bred in Europe during the northern summer?
Know that some British-breeding Dotterels breed in the UK and then fly north to Norway(?)to raise another brood,but realise that this is a different matter entirely to breeding at both "ends" of a migration.
Harry H

Michael Frankis
Thursday 18th September 2003, 22:21
I can see no biological reason why there shouldn't be a bird that breeds twice a year, once at each end of its migration. But I'm not aware of any that actually do so. Several of our summer visitors here use our winter / the southern summer to deal with their main moult, but far from all - many have their main moult while still here in late summer, so they're not doing anything special in Africa.

I suspect the main reason it doesn't happen (other than perhaps exceptionally) is the lop-sided nature of the world's land masses.

The northern hemisphere is full of large continents which get very cold in winter, forcing most of the birds out. The southern hemisphere is mostly water, and what land there is (Antarctica discounted) does not get very cold in winter.

So there's a huge flood of northern hemisphere birds packing into a relatively small southern land area, which is already full of resident birds which are able to live there year-round.

Enough food for everyone perhaps, but not enough to raise an extra brood as well.

One could argue that seabirds might have the option to do so, but they all have such long incubation and fledging times, that they probably just don't have the time to fit in two broods in a year - e.g. Arctic Terns are in Britain for 5 months, add on 2 months migrating time each way, that only leaves 3 months in the winter area, which isn't long enough to get a brood off.

Michael

Joern Lehmhus
Friday 19th September 2003, 12:20
Hi, the only species I remember at the moment, where breeding in the northern and southern hemisphere have been recorded, are European Bee-eater, as Harry already mentioned and White Stork.
If it was the same birds breeding twice in one year, I dont know. I think there was one record for a ringed white stork breeding in Europe and one and a half year later in South Africa...(Ill look it up in my lit this weekend)

but that would be just the odd one out Andy was waiting for
- and nothing happening generally

Joern

logos
Friday 19th September 2003, 12:43
The only brids I know of that breed and then move and then breed again are all technically migrating at the time and stop off during this: Common Quails nest in the Mediterranean region in early spring and then move north and nest again in the summer; some Dotteral nest in Scotland and then move on to the mountains of Norway. perhaps there are more examples of something similar but I do not know of any species breeding at either end of a major migration. I think Michael has summed up the likely reasons well.

Had the White stork nested at either end of its migration within the same year this would probably have been even more unique.

Spud

CJW
Friday 19th September 2003, 12:47
On reflection, I'm not sure. I seem to remember being told - or perhaps I read it somewhere (I sound like Michael Parkinson!) - that some Mexican hummingbird(s) can breed at both ends of the migration?