doozer
Well-known member
Just picked this up on bbc news....
http://news.bbc.co.uk/earth/hi/earth_news/newsid_9418000/9418131.stm
http://news.bbc.co.uk/earth/hi/earth_news/newsid_9418000/9418131.stm
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Cuckoo eggs (1 Viewer)
- Thread starter doozer
- Start date
MJB
Well-known member
The Common Cuckoo is an obligate brood parasite, which means that a Cuckoo that hatches out in, say, a Reed Warbler's nest, is highly likely to return to that habitat when it is an adult to mate. The female Cuckoo will then lay its egges in Reed Warbler nests. The 'highly likely' part means that a small number will return to a different habitat, but if the fertilised eggs are laid in a different host species' nest, then a colour mismatch will risk egg rejection by the host.
Incidentally, because adult Cuckoos migrate earlier than juveniles, these juveniles when returning as adults to the same location where they hatched must have been genetically programmed. Cuckoos do not winter in exactly the same locations as their hosts. Neither is there a special location for all Cuckoos that parasite, say, Reed Warblers.
MJB
Bird Boy
Well-known member
Fortunately for us, the two Cuckoos we have here, Yellow-billed and Black-billed, are not parasitical. Unfortunately, North America has about 60,000,000 Brown-headed Cowbirds that kill an estimated 150,000,000 baby songbirds every year via brood parasitism.
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Actually they are brood parasitic to a limited extent, both on songbirds of various kinds & on their own species. They’re just not obligate parasites like cowbirds & the European Cuckoo.
Sure, cowbirds kill lots of baby songbirds, but then so do many other animals: chipmunks, squirrels, possums, raccoons, snakes, corvids, cats, dogs . . .
Barred Wobbler
Well-known member
That's why baby songbirds exist. Food for others with the lucky few going on to breed and refill the larder.
Very interesting. People automatically assume that the decline of our cuckoo is due to our influence in some way, but it makes you think given the reliance of the species on host species and their possible responses through evolution, that it could be an entirely natural trend.
MJB
Well-known member
Quite a number of cuckoo host species in UK are indicator species, those that are monitored intensively to detect the onset of habitat quality change. Where a habitat of a host species is declining overall, it's likely that a proximate cause is responsible, and that it is human-induced, if indirectly. As the monitoring indications change, countermeasures can be applied via government-authorised procedures without applying anew for permission to do so. It would be good news if we had high numbers of indicator species that all were being monitored, but that presents a resources/funding issue unlikley to be considered until such time economc recovery begins. Of course, the time when such expansion is most need is during economic downturns...
MB
Barred Wobbler
Well-known member
The other side of the coin is what is happening to the cuckoos on their wintering grounds.
A local population near me whose breeding territory is showing no obvious signs of decline - the opposite in fact - were decidedly thin on the ground last year. An almost absolute absence of calling birds in the spring where I normally see three or four and the first cuckoo I saw was on on 23rd July.
Maybe the regulars and last year's offspring failed to survive Africa.
A local population near me whose breeding territory is showing no obvious signs of decline - the opposite in fact - were decidedly thin on the ground last year. An almost absolute absence of calling birds in the spring where I normally see three or four and the first cuckoo I saw was on on 23rd July.
Maybe the regulars and last year's offspring failed to survive Africa.
