Birds reveal the evolutionary importance of love

Date: September 14, 2015

Source: PLOS

Summary: Humans are extremely choosy when it comes to mating, only settling down after a long screening process involving nervous flirtations, awkward dates, humiliating rejections and the occasional lucky strike. But evolution is an unforgiving force — isn’t this choosiness rather a costly waste of time and energy when we should just be ‘going forth and multiplying?’ What, if anything, is the evolutionary point of it all? A new study may have the answer.

Doing a cost/benefit analysis of love is a challenging business, with many potential confounds, and — in the case of humans — some ethical limitations on doing experiments. A new study publishing on September 14th in the Open Access journal PLOS Biology by Malika Ihle, Bart Kempenaers, and Wolfgang Forstmeier from the Max Planck Institute for Ornithology, Seewiesen, Germany, describes an elegant experiment designed to tease apart the consequences of mate choice.

The authors took advantage of the fact that the zebra finch shares many characteristics with humans, mating monogamously for life, and sharing the burden of parental care. Female finches choose mates in a way that is specific to the individual, and there is little consensus among females as to who the cutest male is.

Using a population of 160 birds, the authors set up a speed-dating session, leaving groups of 20 females to choose freely between 20 males. Once the birds had paired off, half of the couples were allowed to go off into a life of wedded bliss. For the other half, however, the authors intervened like overbearing Victorian parents, splitting up the happy pair, and forcibly pairing them with other broken-hearted individuals.

Bird couples, whether happy or somewhat disgruntled, were then left to breed in aviaries, and the authors assessed couples’ behavior and the number and paternity of dead embryos, dead chicks and surviving offspring.

Strikingly, the final number of surviving chicks was 37% higher for individuals in chosen pairs than those in non-chosen pairs. The nests of non-chosen pairs had almost three times as many unfertilized eggs as the chosen ones, a greater number of eggs were either buried or lost, and markedly more chicks died after hatching. Most deaths occurred within the chicks’ first 48 hours, a critical period for parental care during which non-chosen fathers were markedly less diligent in their nest-care duties.

Watching the couples’ courtship showed some noticeable differences — although non-chosen males paid the same amount of attention to their mates as the chosen ones did, the non-chosen females were far less receptive to their advances, and tended to copulate less often. An analysis of harmonious behavior revealed that non-chosen couples were generally significantly less lovey-dovey than the chosen ones. There was also a higher level of infidelity in birds from non-chosen pairs — interestingly the straying of male birds increased as time went by while females roamed less.

Overall the authors conclude that birds vary rather idiosyncratically in their tastes, and choose mates on the basis that they find them stimulating in some way that isn’t necessarily obvious to an outside observer. This stimulation “turns on” the females to increase the likelihood of successful copulation and encourages paternal commitment for the time needed to raise young; together these maximize the couple’s likelihood of perpetuating their genes through their thriving offspring.

Sounds familiar? This is presumably what the human dating game is about, the need perhaps exacerbated by the extended phase of dependence during which our children need parental support. Indeed, these authors’ results are consistent with some studies on the differences between love-based and arranged marriages in human society.


Story Source:

The above post is reprinted from materials provided by PLOS. Note: Materials may be edited for content and length.


Journal Reference:

  1. Malika Ihle, Bart Kempenaers, Wolfgang Forstmeier. Fitness Benefits of Mate Choice for Compatibility in a Socially Monogamous Species. PLOS Biology, 2015; 13 (9): e1002248 DOI: 10.1371/journal.pbio.1002248
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How Do Songbirds Sing? In 3-D!

Jan. 8, 2013 — The question ‘How do songbirds sing?’ is addressed in a study published in BioMed Central’s open access journal BMC Biology. High-field magnetic resonance imaging and micro-computed tomography have been used to construct stunning high resolution, 3D, images, as well as a data set “morphome” of the zebra finch (Taeniopygia guttata) vocal organ, the syrinx.

High-field magnetic resonance imaging and micro-computed tomography have been used to construct stunning high resolution, 3D, images, as well as a data set “morphome” of the zebra finch (Taeniopygia guttata) vocal organ, the syrinx. (Credit: Daniel N Düring, Alexander Ziegler, Christopher K Thompson, Andreas Ziegler, Cornelius Faber, Johannes Müller, Constance Scharff and Coen P H Elemans.)

 

Like humans, songbirds learn their vocalizations by imitation. Since their songs are used for finding a mate and retaining territories, birdsong is very important for reproductive success.

The syrinx, located at the point where the trachea splits in two to send air to the lungs, is unique to birds and performs the same function as vocal cords in humans. Birds can have such a complete control over the syrinx, with sub-millisecond precision, that in some cases they are even able to mimic human speech.

Despite great inroads in uncovering the neural control of birdsong, the anatomy of the complex physical structures that generate sound have been less well understood.

The multinational team has generated interactive 3D PDF models of the syringeal skeleton, soft tissues, cartilaginous pads, and muscles affecting sound production. These models show in detail the delicate balance between strength, and lightness of bones and cartilage required to support and alter the vibrating membranes of the syrinx at superfast speeds.

Dr Coen Elemans, from the University of Southern Denmark, who led this study, explained, “This study provides the basis to analyze the micromechanics, and exact neural and muscular control of the syrinx. For example, we describe a cartilaginous structure which may allow the zebra finch to precisely control its songs by uncoupling sound frequency and volume.” In addition, the researchers found a previously unrecognized Y-shaped structure on the sternum which corresponds to the shape of the syrinx and could help stabilize sound production.


Story Source:

The above story is reprinted from materials provided byBioMed Central Limited, via AlphaGalileo.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.


Journal Reference:

  1. Daniel N Düring, Alexander Ziegler, Christopher K Thompson, Andreas Ziegler, Cornelius Faber, Johannes Müller, Constance Scharff and Coen P H Elemans. The songbird syrinx morphome: a three-dimensional, high-resolution, interactive morphological map of the zebra finch vocal organBMC Biology, 2013; (in press) [link]
BioMed Central Limited (2013, January 8). How do songbirds sing? In 3-D!. ScienceDaily. Retrieved January 10, 2013, from http://www.sciencedaily.com/releases/2013/01/130107190756.htm