Thursday, October 02, 2008

Female Birds Sacrifice Health During Egg Production

Bright blue eggs made by female birds, such as those created by flycatchers, do not come at no cost. Females sacrifice a portion of their own health in an attempt to make their eggs as colorful as possible. Males of these species do not always stay with the female to tend to the young. The brighter the eggs, the more likely the male will stay with the female. The male is able to gauge the health of the female according to how bright and colorful the eggs are.

The blue cue of the eggs comes from bilverdin, a compound created from the breakdown of hemoglobin. The function of bilverdin is not only being blue dye for the eggs but it is also an antioxidant which prevents cellular damage. The female bird trades off her own health and resources in an attempt to persuade the male that he should help with the young . The brighter the eggs are, the healthier the young is likely to be, and the more likely the male will stay.

A study conducted by Judith Morales and the University of Viog tested the levels of bilverdin in the blood of female pied flycatchers. The sample they were testing were located in one hundred boxes in central Spain. In order to stress the females, the researchers removed the nests once they were almost complete and allowed the female to create a new nest. After building their second nest, the females then began to lay their eggs. The researchers then recorded the color of the eggs and took a blood sample from the female one week after they had laid the eggs. Neither the stress of having to rebuild a nest nor having vibrant blue eggs alone indicated a large decrease of bilverdin in blood, but when combined there was a noticeable difference. The levels of bilverdin in the blood become measurable when birds are under the effects of stress.

Click here for the original article, "Female Birds Sacrifice Health to Create More Colourful Eggs," by Matt Kaplin.

Rob Lubenow (3)

Update 10-07-08:
This one of the first studies as well as the first proof that female birds sacrifice their own health to help keep the males around. This sacrifice of the female's health to turn her eggs bright blue does have serious benefits. By increasing the chances of keeping the male around, there is an increase of the chance of survival of the young chicks. Offspring will have two parents caring for them instead of one, more protection from other birds or predators, and for some species a guaranteed father there during critical periods for song development. The male flycatchers mate with different females throughout the different mating seasons. Since this is a relatively new study the evolution of the trait has not yet been defined. In the future they will most likely have an even greater understanding concerning this female health sacrifice.


At 11:57 PM, Blogger PWH said...

Very interesting..I would have never guessed that brighter colored eggs would correlate with male tendencies to stay with their mates and help tend to the young. I truly wonder how this feature, the ability to detect the fitness of offspring by the egg brightness evolved within males in this species.

-Joanne Philippeaux

At 9:02 PM, Anonymous Allison Cornell said...

I found this article extremely interesting. I had no idea that the color of bird eggs signified anything to the birds other than, perhaps, what species the eggs belonged. Do other species of birds use egg coloration or color patterns to indicate similar or different things? How much does the female suffer from making the eggs bluer? What kind of repercussions can it have on her? If they are not blue enough, does the male just leave, or do they take any other actions, such as killing the eggs, etc.?

Allison Cornell (3)

At 12:54 PM, Blogger PWH said...

This comment has been removed by the author.

At 1:05 PM, Blogger PWH said...

Very interesting article. I was just wondering if there was any mention of just how much the presence of the male increases the chance of the chick's survival (percentage wise)?

-Benjamin Spozio

At 9:15 PM, Anonymous Anonymous said...

What of the female's health is being traded off to make a colorful egg? How long does the male stay with the female and the chick?


At 9:31 PM, Blogger PWH said...

I found this topic of trading health for the survival of the offspring interesting. Are the male flycatchers monogomous after they see the health of the young and remain to care for them? Or do they mate with different females the following spring? Also, is this trait in the female birds something that has evolved or may evolve into something less harmful to them in the future? Or has this always been the means to attract the male to remain in this species?

Ahmed Sandakli


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