Featured Research

from universities, journals, and other organizations

Researchers crack cuckoo egg mystery

Date:
September 22, 2010
Source:
University of Sheffield
Summary:
Researchers have discovered that cuckoo eggs are internally incubated by the female bird for up to 24 hours before birth, solving for the first time the mystery as to how a cuckoo chick is able to hatch in advance of a host's eggs and brutally evict them.

Female cuckoo at reed warbler.
Credit: O. Mikulica

Researchers at the University of Sheffield have discovered that cuckoo eggs are internally incubated by the female bird for up to 24 hours before birth, solving for the first time the mystery as to how a cuckoo chick is able to hatch in advance of a host´s eggs and brutally evict them.

Published September 22, 2010 in the journal Proceedings of the Royal Society of London, Series B, the research shows that internal incubation allows the cuckoo chick to hatch before its nest mates, evict them, and monopolise the food brought by the foster parents.

Although previous studies have suggested early hatching is achieved partly through the cuckoo producing a small egg which develops faster, it has long been suspected that there might be another reason for this.

A team from Sheffield, headed up by Professor Tim Birkhead, from the University´s Department of Animal and Plant Sciences, worked with cuckoo researchers across Europe, to examine the newly laid eggs of eight cuckoos, and discovered that each one was at a more advanced stage than is normal among small birds. To test the idea that this advanced development was a result of the female cuckoo retaining the egg inside her, they simulated `internal incubation´ in another species; the zebra finch.

The researchers took recently laid finch eggs and incubated them for 24 hours at body temperature, which is 40oC in both the finch and the cuckoo. After this time, the zebra finch eggs were at the same stage as the cuckoo eggs at the time they were laid.

Superficially this suggested that the internal incubation gives the cuckoo a 24 hour head start over its host´s eggs, but the researchers discovered it is in fact more than this.

When eggs are incubated by the adult birds in the nest, their eggs are at about 36oC. Inside the female, the egg is at a body temperature of 40oC. This difference in temperature means that 24 hours at 40oC gives the cuckoo egg a 31 hour head start over the host eggs.

Most birds release their ovum or the yolk of the egg from the ovary 24 hours before it is laid. Fertilisation occurs within 15 minutes of ovulation, and the ovum then spends about 24 hours having the albumen, or egg white, and the shell put on to form a normal egg. This fully formed egg is laid 24 hours after ovulation. Significantly, about six hours after the ovum is fertilised, the microscopic embryo begins to develop and by the time the egg is laid, the embryo contains some 10,000 cells. It is only after two days of incubation that there are any signs, visible to the naked eye, that the egg is developing and an embryo forming.

In the cuckoo however, the team demonstrated that the egg is ovulated and fertilised and then six hours later embryo development begins. As the egg passes down the oviduct, or egg tube, the white and shell are added, and once the egg is fully formed, about 24 hours after it was released from the ovary, it then sits in the female´s oviduct for a further 24 hours. In other words, by the time the cuckoo egg is laid, it has had 18 to 24 hours of internal incubation at 40oC and hatches 31 hours ahead of any host egg laid at the same time.

Professor Tim Birkhead, from the Department of Animal and Plant Sciences at the University of Sheffield, said: "The idea of internal incubation in birds has until now been considered impossible because it was assumed that female birds could not hold onto a fully formed egg. In fact, the idea of internal incubation by cuckoos was suggested as early as 1800, but then ignored. Our results show that internal incubation gives cuckoo chicks that crucial head start in life, allowing them to dispose of their nest mates -- a superb adaptation to being a brood parasite."


Story Source:

The above story is based on materials provided by University of Sheffield. Note: Materials may be edited for content and length.


Journal Reference:

  1. Birkhead, T. R., Hemmings, N., Spottiswoode, C. N., Mikulica, O., Moskát, C., Bán, M. & Schulze-Hagen, J. Internal incubation and early hatching in brood parasitic birds. Proceedings of the Royal Society of London, Series B, 22 September 2010

Cite This Page:

University of Sheffield. "Researchers crack cuckoo egg mystery." ScienceDaily. ScienceDaily, 22 September 2010. <www.sciencedaily.com/releases/2010/09/100922102247.htm>.
University of Sheffield. (2010, September 22). Researchers crack cuckoo egg mystery. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2010/09/100922102247.htm
University of Sheffield. "Researchers crack cuckoo egg mystery." ScienceDaily. www.sciencedaily.com/releases/2010/09/100922102247.htm (accessed July 25, 2014).

Share This




More Plants & Animals News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Boy Attacked by Shark in Florida

Boy Attacked by Shark in Florida

Reuters - US Online Video (July 24, 2014) — An 8-year-old boy is bitten in the leg by a shark while vacationing at a Florida beach. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
Goma Cheese Brings Whiff of New Hope to DRC

Goma Cheese Brings Whiff of New Hope to DRC

Reuters - Business Video Online (July 24, 2014) — The eastern region of the Democratic Republic of Congo, mainly known for conflict and instability, is an unlikely place for the production of fine cheese. But a farm in the village of Masisi, in North Kivu is slowly transforming perceptions of the area. Known simply as Goma cheese, the Congolese version of Dutch gouda has gained popularity through out the region. Ciara Sutton reports. Video provided by Reuters
Powered by NewsLook.com
Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Newsy (July 24, 2014) — A new study claims a set of prehistoric T-Rex footprints supports the theory that the giant predators hunted in packs instead of alone. Video provided by Newsy
Powered by NewsLook.com
Bill Gates: Health, Agriculture Key to Africa's Development

Bill Gates: Health, Agriculture Key to Africa's Development

AFP (July 24, 2014) — Health and agriculture development are key if African countries are to overcome poverty and grow, US software billionaire Bill Gates said Thursday, as he received an honourary degree in Ethiopia. Duration: 00:36 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

      Environment News

        Technology News



          Save/Print:
          Share:  

          Free Subscriptions


          Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

          Get Social & Mobile


          Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

          Have Feedback?


          Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
          Mobile iPhone Android Web
          Follow Facebook Twitter Google+
          Subscribe RSS Feeds Email Newsletters
          Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins