Cuckoo chicks in Zebra finches

Apr 22, 2010
Image: Max Planck Institute for Ornithology, Seewiesen

( -- Some female zebra finches foist a part of their eggs on their neighbours. Scientists of the Max Planck Institute for Ornithology in Seewiesen discovered that in every fifth nest there is one egg that is not produced by its social parents. The female birds act in a very well-targeted way: eggs are being placed in "foster-care" shortly before the hosts commence their own egg laying (online publication in Animal Behaviour, April 15, 2010).

Zebra finches breed in colonies and each pair cares for their own offspring. However, brood parasitism within the same species is relatively common, in captive populations as well as in the wild in Australia. Scientists of the Max Planck Institute in Seewiesen studied the parentage of all in a captive population with genetic methods and found out that in every 20 eggs there was one "cuckoo egg". Mostly the same females specialize in outsourcing parental work of some of their eggs. It is interesting that they combine brood parasitism with laying and raising their own clutches - a purely parasitic strategy was not found.

The female cuckoo-zebra finches have to time the egg-laying to a host nest very precisely: the starts usually shortly after laying the first or second egg. When the parents are already sitting on their nest, it is hardly possible to foist a cuckoo egg on them. But if the female drops the egg too early to a host's nest, the latter might abandon the nest. Captive conditions in the aviaries made thorough studies of the chronology of egg laying easier for the scientists: "Most of the cuckoo eggs show up in the host’s nest shortly before the host parents start breeding," says Holger Schielzeth, first author of the study. "That shows that the "cuckoo-females" seem to monitor the neighbours' breeding start". The researchers found no cues that the cuckoo females target specific host pairs. More the opposite was the case: a host pair was rarely hit a second time. That is a sign that host parents learn to defend themselves.

Cuckoo females usually lay more than one egg in host nests, but most of the time only one in each nest and shortly before they start laying their own clutches. However the cuckoo strategy is not as successful as it might sound: "Just one third of the eggs are finally being reared by foster parents", says Holger Schielzeth. "Females employing a mixed brood strategy lay more eggs but end up with as many fledglings as females with a pure brood strategy". If the brood would be a more successful strategy, the development of a pure cuckoo-specialist within the would probably have evolved.

Explore further: Insect mating behavior has lessons for drones

More information: Holger Schielzeth and Elisabeth Bolund, Patterns of conspecific brood parasitism in zebra finches, Animal behaviour. Published online April 15, 2010. DOI:10.1016/j.anbehav.2010.03.006

Related Stories

Birds' strategic mobbing fends off parasitic invaders

Jan 29, 2009

Reed warblers use mobbing as a front line of nest defense against parasitic cuckoos, according to a new report published online on January 29th in Current Biology, a Cell Press publication. Cuckoos act as parasites by lay ...

How birds spot the cuckoo in the nest

Jul 15, 2008

It's not always easy spotting the cuckoo in the nest. But if you don't, you pay a high price raising someone else's chick. How hosts distinguish impostor eggs from their own has long puzzled scientists.

Birds use social learning to enhance nest defense

Jun 04, 2009

Reed warblers live with the threat that a cuckoo bird will infiltrate their nest, remove one of their eggs, and replace it with the cuckoo's own. This 'parasitism' enables the cuckoo to have its young raised by unsuspecting ...

Cuckoo's copying an evolutionary curiosity

Mar 31, 2010

( -- A new study of brood parasitism in birds has shown that the nest-poaching New Zealand shining cuckoo's ability to mimic its grey warbler host is an evolutionary curiosity.

Recommended for you

Insect mating behavior has lessons for drones

5 hours ago

Male moths locate females by navigating along the latter's pheromone (odor) plume, often flying hundreds of meters to do so. Two strategies are involved to accomplish this: males must find the outer envelope ...

Godwits are flexible... when they get the chance

May 29, 2015

Black-tailed godwits are able to cope with unpredictable weather. This was revealed by a thorough analysis of the extraordinary spring of 2013 by ecologist Nathan Senner of the University of Groningen and ...

Do you have the time? Flies sure do

May 28, 2015

Flies might be smarter than you think. According to research reported in the Cell Press journal Current Biology on May 28, fruit flies know what time of day it is. What's more, the insects can learn to con ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.