Sexual Selection, Hormones, and Social Behavior

BrightmaleWelklin.jpg

How and why do males produce flashy signals? 

In the photos above, why is the male on the left brown and cryptic, while the male on the right is red-black and flashy, does this matter, and how does it happen? Those questions are effectively my PhD dissertation. 

For Red-backed Fairy-wrens, the species shown above, most males remain in brown plumage during their first breeding season, but some males molt into red-black plumage before their first breeding season. By their second year of age nearly all males take on red-black plumage before they breed. Previous research has shown that females prefer to mate with males in red-black plumage over males in brown plumage, so why wouldn't all males produce into red-black plumage for the breeding season?  

My research is looking at the possible social costs of molting into bright plumage. Social regulation of signals has been well-reported in other animal systems and individuals that attempt to cheat the system, or produce a signal that encodes information about their condition or strength that is not true, often suffer increased aggression from their neighbors. In a similar way, my hypothesis is that if a young male molts into bright plumage he's going to become another competitor for the old red-black males nearby to gain mating opportunities with females. Old red-black males that see a younger male molting into red-black plumage may behave more aggressively towards him to prevent him from molting or to drive him from their social group. It's possible that in order for a young male to molt into red-black plumage he must be able to fend off aggressive bright males or be in an social context that lacks bright males. 

Low-amplitude Song in Birds

Everyone who's spent time outside has heard a bird sing. Most of the songs you hear are known as high-amplitude, long-range songs, but did you know many bird species have a entirely different repertoire of soft, low-amplitude songs? For my undergraduate research, I worked with Dustin Reichard, to study the function of low-amplitude songs in Dark-eyed Juncos, a common North American songbird. For my senior honors thesis at Indiana University I looked into the prevalence and function of low-amplitude in North American Birds. We found that low-amplitude songs and calls are fairly common across birds and that low-amplitude songs were more likely to used in courtship contexts than in aggressive interactions. Read the paper in The Auk