Birds do it.
HELLO. S.E.X. Chirp. Mature post!
The birds are certainly chirping in our hood these past few weeks. Maybe it is just Spring in the air. Maybe it’s just romance. Let’s fall in love.
Sex and single bird.
Written by researchers around the world, highlights new discoveries in the sciences and what they mean for your outlook.
hawks do it
macaws do it
peacocks do it
ostriches do it
flamingos do it
A parakeet does it
THE BIG IDEA: Every summer, male songbirds called lark buntings shed their dull winter plumage and fly north from Mexico and Texas to build ground nests on the short-grass prairie of the Pawnee National Grassland, northeast of Denver. By the time female birds arrive two weeks later, the males are brightly adorned, often with glossy black feathers and white wing patches that flash as they zoom skyward and float back to the ground, singing all the while. These fancy traits and aerial displays may ward off other males, and they also send a come-hither signal to females. Scientists have always assumed that female birds, looking for good fathers, consistently choose males that exhibit the same exaggerated sexual traits. But my research shows that their preferences change from year to year. Sometimes females even select partners that look completely different from the previous season’s mates.
HOW WE DISCOVERED IT: For five summers, I teamed up with Bruce Lyon, a biologist at the University of California at Santa Cruz. We lured male birds to baited feeders, tagged them with colored bands, took blood samples and documented their traits — from body and wing-patch color to body and beak size. Then we released the birds and used binoculars to follow their breeding success. When the chicks hatched, we ran paternity tests and tracked the number of offspring fathered by each male.
WHAT WE FOUND: For male lark buntings, reproductive success depends on whatever traits are in vogue among females that season. By staying flexible and seeking out partners with the physical qualities most needed at the moment, females ensure that more chicks successfully leave the nest. If the prairie is overrun by ground snakes, for example, mother birds might choose the most protective males — a quality that might be signaled by wing-patch size. If grasshoppers are scarce the next year, maybe they will look for partners with big beaks, which might make them good providers.
WHY IT MATTERS: Female mating preferences are nothing new — female guppies look for males with bright orange and black spots, for example — but scientists generally believed that those preferences were fixed, as if coded into the species’ genes. Now we’ve shown that female birds can change their minds from year to year, which means that they help drive genetic variation. So what might explain the many bright colors and elaborate songs of birds of paradise? The woman’s prerogative. —Alexis Chaine is a researcher at the National Center for Scientific Research in Moulis, France
In cooperation withScience magazineand theAmerican Association for the Advancement of Science. To see videos of lark buntings, visit the Web sitewww.sciencemag.org/wpoutlook. via
Science: X + Y
We’ve all heard about the birds and the bees. But apparently when it comes to birds, they have an unusual take on his and hers — and the difference is genetic. Species with differentiated sex chromosomes (X and Y in humans, for example) get around the fact that males and females get different-sized portions of sex chromosome genes with a balancing act geneticists call dosage compensation. But research published in the Journal of Biology shows that birds are extraordinary, because some bird genomes can live with an apparent overdose of sex-related genes.
US researchers Itoh, Melamed et al. working in Arthur Arnold’s University of California, Los Angeles laboratory used RNA microarray analysis for their dosage compensation study. The team sampled chickens and zebra finches, and compared the results with data from humans and mice. In several types of finch and embryonic chicken brain tissue, Z chromosome genes were expressed up to 40% higher in ZZ males than ZW females. This contrasts with findings from the mammal samples, where dosage compensation meant that the male: female ratio of X-linked genes is similar to that of autosomal genes.
In mammals, mismatched doses of X genes between males and females threaten to upset the gene network in one or both sexes. Fruit flies (Drosophila), roundworms (C. elegans) and humans each work around this dosage problem using different molecular pathways. By contrast, for birds it appears that most genes on the Z chromosome are not fully dosage-compensated, at least at the transcriptional level.
The study challenges current thinking about the role and mechanisms of dosage compensation in species with heteromorphic sex chromosomes. “Unlike mammals, birds have an ineffective dosage compensation,” says Arnold. “The finding is surprising because dosage compensation was previously thought to be critical for survival. Birds, however, seem to be doing just fine without sexual equality of Z gene expression”. via Science Daily
Maureen Adams
May 16th, 2008 at 9:57 am
Friday Ark #191…
We’ll post links to sites that have Friday (plus or minus a few days) photos of their chosen animals (photoshops at our discretion and humans only in supporting roles). Watch the Exception category for rocks, beer, coffee cups, and….? Visit all the …