The Naked Scientists

The Naked Scientists Forum

Author Topic: How do cuckoo's hide their eggs in other bird's nests?  (Read 1575 times)

Offline thedoc

  • Forum Admin
  • Administrator
  • Sr. Member
  • *****
  • Posts: 511
  • Thanked: 12 times
    • View Profile
David asked the Naked Scientists:
   What processes, in terms of biology, are involved on how a Cuckoo manages to produce an egg which looks exactly like the egg(s) of the host bird to which their chick will be part of.

In other words, when a Cuckoo see's an egg of a particular species of bird, how does it manage to create an egg which mimics the exact design, colour and shape of the egg?

What processes are involved where the chick of the Cuckoo manages to know how to get rid of the other eggs/chicks in the nest so it is the only one in which to survive?

Obviously, the Cuckoo does not physically make the replica egg (open to interpretation) but how exactly is the information (using the eyes) about the host egg transferred onto the egg the Cuckoo lays into the nest of the host species of bird to which it is replicating?
What do you think?
« Last Edit: 04/12/2015 17:50:02 by _system »


 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8125
  • Thanked: 53 times
    • View Profile
Re: How do cuckoo's hide their eggs in other bird's nests?
« Reply #1 on: 04/12/2015 21:33:47 »
   What processes, in terms of biology, are involved on how a Cuckoo manages to produce an egg which looks exactly like the egg(s) of the host bird to which their chick will be part of.

Generally Natural selection , ( & in this case imprinting ).

In other words, when a Cuckoo see's an egg of a particular species of bird, how does it manage to create an egg which mimics the exact design, colour and shape of the egg?
It's not necessary for an animal to see anything to be camouflaged, or produce camouflaged eggs. Over time natural-selection favours the survival of those whose fur/feathers/eggs are a better match for the environment.
« Last Edit: 04/12/2015 23:17:42 by RD »
 

Offline evan_au

  • Neilep Level Member
  • ******
  • Posts: 4113
  • Thanked: 245 times
    • View Profile
Re: How do cuckoo's hide their eggs in other bird's nests?
« Reply #2 on: 05/12/2015 00:00:26 »
Quote from: David
how exactly is the information (using the eyes) about the host egg transferred onto the egg the Cuckoo lays into the nest of the host species of bird to which it is replicating?
The Cuckoo bird is not a 3D scanner and 3D printer - it does not copy the pattern on the target egg, and print it onto its own egg.

You could test this by placing a Cuckoo in a cage, with no view of the target eggs in its entire life. The Cuckoos eggs will still look like the target egg.

The answer is in the genes of the Cuckoo bird. These dictate what colors and patterns will appear on the Cuckoo egg.

Different species of Cuckoo which target different host species have different genes to color their eggs - and presumably, different genes which govern their behavior so they know which kind of eggs they will lay their egg alongside.

There are other complex behavioral traits involved in cuckoo behavior, as you note.

There are many forms of mimicry in nature, and biologists have attributed them to various modes of natural selection.

...RD beat me by a minute!
 

Offline Don_1

  • Neilep Level Member
  • ******
  • Posts: 6890
  • Thanked: 7 times
  • A stupid comment for every occasion.
    • View Profile
    • Knight Light Haulage
Re: How do cuckoo's hide their eggs in other bird's nests?
« Reply #3 on: 05/12/2015 16:56:14 »
Since the egg's calcareous shell is and its pigmentation is laid on the shell membrane in the uterus before it hardens and passes out through the cloaca, the Cuckoo cannot imprint the egg to resemble the eggs in the nest it chooses to lay in.

As RD & Evan have eluded to, there is an element of natural selection going on here.

A cuckoo cannot lay its egg in just any nest since it must have an egg ready to lay as soon as it finds a suitable host.

The cuckoo will return to familiar territory to lay its eggs to that in which it fledged. Therefore the nests it will find will be of the same species to that which raised it. So the egg it has ready to lay will already mimic the eggs of the host's. Typically, here in the UK these will be Reed Warblers, Meadow Pipits and Dunnocks. A Cuckoo raised by Reed Warblers will look for a Reed Warbler's nest. It would not be able to switch to a Dunnock's nest as the two eggs are very different.

But this is not the only strategy used by the Cuckoo. Some Cuckoo species and other parasite birds, such as the Brown Headed Cowbird use Mafia tactics. The female will watch the nest in which she lays her egg. If the host pushes out the Cuckoo's egg, the female Cuckoo will return to the nest and throw out the host's eggs. These host birds have come to learn that it is better to raise an extra chick than to loose all their own. In these cases, the eggs may not mimic the host's eggs.

In the case of the Brown Headed Cowbird and the Great Spotted Cuckoo, it is also thought that the large fledgling may even serve as a bonus to the host's chicks by deterring predators.
« Last Edit: 05/12/2015 17:00:42 by Don_1 »
 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8125
  • Thanked: 53 times
    • View Profile
Re: How do cuckoo's hide their eggs in other bird's nests?
« Reply #4 on: 06/12/2015 01:00:16 »
The cuckoo will return to familiar territory to lay its eggs to that in which it fledged. Therefore the nests it will find will be of the same species to that which raised it.

I believe the cuckoo is imprinted with the appearance of the host birds who fed it, rather than the appearance of the nest it hatched in , ( that imprinting is how it "knows" to parasitize the same type of host bird when it becomes adult ).
« Last Edit: 06/12/2015 01:06:19 by RD »
 

Offline Don_1

  • Neilep Level Member
  • ******
  • Posts: 6890
  • Thanked: 7 times
  • A stupid comment for every occasion.
    • View Profile
    • Knight Light Haulage
Re: How do cuckoo's hide their eggs in other bird's nests?
« Reply #5 on: 07/12/2015 10:39:17 »
While the host bird will undoubtedly be imprinted, there must also be habitat imprinting for the female Cuckoo to return to a location where it is most likely to find the right host. This may not be an exact location, but a similar type of habitat.

A Cuckoo raised by a Reed Warbler must return to low lying fen land and search through the reed beds if it is to find a Reed Warbler nest. Searching through woodland, this Cuckoo might find the nests of Dunnocks, but lay its egg there and the brownish egg mimicking the Reed Warbler egg would stand out like a sore thumb against the blue egg of the Dunnock.

It must therefore follow that the Cuckoo chick must imprint its habitat type and very possibly even the position and build of the nest. For a Reed Warbler raised Cuckoo to simply return to fen land in search of a suitable nest to lay its egg in would be insufficient information. It needs to know to look for the well hidden Reed Warbler nest down in-between  the tall stems of the reeds. If this can be imprinted, then I see no reason why the chick cannot also be imprinted with the colour, pattern and size of the other eggs within the nest.

 

The Naked Scientists Forum

Re: How do cuckoo's hide their eggs in other bird's nests?
« Reply #5 on: 07/12/2015 10:39:17 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums
 
Login
Login with username, password and session length