A Fascination With Birds

Have you ever wondered why there are so many strikingly beautiful male birds? Or maybe why birds produce such a large array of complex, often melodic sounds? What about why some birds have developed such elaborate ornamentation and courtship displays that you would almost need to see to believe?

The male Resplendent Quetzel has an extremely large and beautiful tail streamer up to 65 cm long. Image by Phoo Chan (https://www.flickr.com/photos/mallardg500/13950167241)

Being a bird lover, these are just a few of the questions I have pondered over the years. While there are many factors to consider when determining why birds have evolved such a staggering amount of exceptional and often extreme behavioural and morphological traits, it is now widely accepted that sexual selection plays a major role in much of what we see today in the bird world.

Extreme ornamentation displayed by a male tufted coquette hummingbird. Sourced from https://au.pinterest.com/pin/205195326749461523/

 Charles Darwin (1906) first developed the theory of sexual selection which he described as:

“the advantage which certain individuals have over other individuals of the same sex and species solely in respect of reproduction”.  

In other words, sexual selection can be thought of as intra-specific reproductive competition (Hosken & House 2011). While it was suggested by some that it was not needed to distinguish sexual selection from natural selection, Darwin wanted to explain how characters could exist in organisms whose functions were often deleterious to the individual's survival and apparently not favoured by natural selection (Darwin 1906, Hosken & House 2011). He stated that sexual selection often: 

“depends not on the struggle for existence, but on the struggle between males for possession of females.” 

Darwin also recognised that it was not only competition, primarily between males, that acted as a mechanism of sexual selection, but also the choosiness of females when selecting a mate (Darwin 1906, Hosken & House 2011).

A peacock displaying his brilliant plumage to what looks like a very uninterested and possibly choosy female. Image sourced from http://www.buzzle.com/articles/difference-between-male-and-female-peacocks.html

Over the coming weeks I will be sharing with you specific examples of incredible and diverse sexually selected characters including song, plumage, scent, cognitive skills and elaborate displays that have fueled my continuing fascination with birds. Hopefully over the next 9 weeks I can show you why I think birds and the incredible diversity they display are an endless source of wonder and provide an insight into their complex and often mysterious world.

The male Satin Bowerbird uses blue objects to adorn his bower, luring in the dull coloured female before performing his courtship display. Image by Gerhard Koertner (http://www.bbc.com/earth/story/20141119-the-barmy-courtship-of-bowerbirds)

 


References
Darwin, C 1906, The descent of man and selection in relation to sex, 2nd edn, Murray, London
Hosken, DJ & House, CM 2011, "Sexual selection", Current Biology, vol. 21, no. 2, pp. R62-R65