When it comes down to getting it on, there are generally two different approaches to finding a partner. If you want to minimize the risk of not finding a partner, or just aren’t that picky, you might go all out with everyone you attempt to woo – the movie, the dinner, flowers, everything. On the other hand, if you’re willing to be choosy you might focus all your effort on one person and take the risk of being rejected. While you – as a human – might take someone out on a date, male Bengalese finches communicate their interest with songs.
A recent study in the journal Animal Behaviour investigated the methods male Bengalese finches use to court females. The goal of this research was to determine if and how male Bengalese finches, Lonchura striata domestica, express preferences for female finches. In order to test this, the researchers presented male finches with one female finch at a time. The male and female finches were separated by mesh and were given one hour with each other. During this time, the male finches’ songs were recorded, as well as the orientation of the bird. Males could either direct their songs at their captive audience, or show their ambivalence by singing to their cage. The researchers assumed that male finches do not play hard to get.
Male finch songs were categorized in three ways: undirected (UNDIR) songs were songs sung while facing away from the female finch, early directed (DIRearly) songs were songs that were sung to the female early in the interaction, and late directed (DIRlate) songs were directed songs that occurred late in the interaction. Distinguishing between early and late directed songs is important for analyzing how the songs change over the course of the interaction. Each song was also characterized by its overall note transition entropy, which is the weighted sum of the probability of a transition following each note in the song. In other words, the more random note changes a song has, the higher its note transition entropy is, while the more structured the song is, the lower its note transition entropy is.
So what did the male finches do? The male finches almost always engaged in some courtship behavior and sang at least one song to each female. This early song usually varied wildly in entropy between different females, but was consistent for each female. The authors conclude that males sing different courtship songs for different females.
However, the amount of interaction varied greatly after the initial courtship. It turns out that the male finches tended to focus on a single female of their choice, dedicating around 44% of their songs to her. Those females were also the ones that males made the biggest effort to impress, at least at first – the early directed song was most structured. Male finches expressed their mating preferences by varying the number of songs they sung and, at least early in the interaction, the note variation in those songs. DIRearly songs generally had less entropy and were more structured than undirected songs. These early songs were generally well received by the females. However, later in the interaction the male finches got lazy – the late directed songs were less structured, regardless of the female, and the females responded less strongly to them.
Overall, mating in Bengalese finches seems to be based on mutual mate choice. If the female is receptive to the initial courtship song, the male finch can choose to continue the interaction. Perhaps if humans could express their relationship interests in a song, dating would be a lot easier.
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| [1] Bengalese (Society) Finch |
A recent study in the journal Animal Behaviour investigated the methods male Bengalese finches use to court females. The goal of this research was to determine if and how male Bengalese finches, Lonchura striata domestica, express preferences for female finches. In order to test this, the researchers presented male finches with one female finch at a time. The male and female finches were separated by mesh and were given one hour with each other. During this time, the male finches’ songs were recorded, as well as the orientation of the bird. Males could either direct their songs at their captive audience, or show their ambivalence by singing to their cage. The researchers assumed that male finches do not play hard to get.
Male finch songs were categorized in three ways: undirected (UNDIR) songs were songs sung while facing away from the female finch, early directed (DIRearly) songs were songs that were sung to the female early in the interaction, and late directed (DIRlate) songs were directed songs that occurred late in the interaction. Distinguishing between early and late directed songs is important for analyzing how the songs change over the course of the interaction. Each song was also characterized by its overall note transition entropy, which is the weighted sum of the probability of a transition following each note in the song. In other words, the more random note changes a song has, the higher its note transition entropy is, while the more structured the song is, the lower its note transition entropy is.
[2]
So what did the male finches do? The male finches almost always engaged in some courtship behavior and sang at least one song to each female. This early song usually varied wildly in entropy between different females, but was consistent for each female. The authors conclude that males sing different courtship songs for different females.
However, the amount of interaction varied greatly after the initial courtship. It turns out that the male finches tended to focus on a single female of their choice, dedicating around 44% of their songs to her. Those females were also the ones that males made the biggest effort to impress, at least at first – the early directed song was most structured. Male finches expressed their mating preferences by varying the number of songs they sung and, at least early in the interaction, the note variation in those songs. DIRearly songs generally had less entropy and were more structured than undirected songs. These early songs were generally well received by the females. However, later in the interaction the male finches got lazy – the late directed songs were less structured, regardless of the female, and the females responded less strongly to them.
Overall, mating in Bengalese finches seems to be based on mutual mate choice. If the female is receptive to the initial courtship song, the male finch can choose to continue the interaction. Perhaps if humans could express their relationship interests in a song, dating would be a lot easier.
Journal Citation:
Heinig, Abbie, Santosh
Pant, Jeffery L. Dunning, Aaron Bass, Zachary Coburn, and Jonathan F. Prather.
2014. “Male Mate Preferences in Mutual Mate Choice: Finches Modulate Their
Songs across and within Male–female Interactions.” Animal Behaviour 97 (November): 1–12.
doi:10.1016/j.anbehav.2014.08.016.
Media Credits:
[1] Photo by Nathan Rupert, https://flic.kr/p/copsGJ
[2] Video by Youtube user cathytai, http://www.youtube.com/watch?v=McUJG_877Ks
Interesting article! I wish you'd given more explicit instructions on how I myself could woo a lady finch. Either way, I wonder how situational a male's preferences for particular females are. Is he predisposed to be interested in a certain type of female, or do his preferences change with availability?
ReplyDeleteI liked the addition of the video to your blogpost, as well as the engaging intro :)
ReplyDeleteI was wondering if the paper wrote a little more on their assumption that male finches don't play hard to get. What research or basis did the authors have to make this assumption?
Thanks for the blog post, it was really interesting! I like how the researchers analyzed the song structure and effectiveness over time. I wonder why the directed songs got "lazier" as time went on. I didn't expect that - I expected that males would use more structured songs for their favorite female, but keep the structure constant over time. That was a surprising result for me.
ReplyDeleteMaybe the males only keep singing to females that show some interest, so it is less important to be super impressive as time goes on? Or maybe it is cognitively demanding, and they can't really maintain it for a long time?
DeleteFirst of all, I should correct you that song may be used as a human mate attractant...or repellant, as the case may be. I've had...mixed results with that strategy.
ReplyDeleteAlso, I'm curious about the reasons for song entropy. Were unstructured songs easier to produce, and so used to attempt to generally attract females, while structured songs would 'seal the deal'? Also, what does the structure tell the females about male quality? Overall vocalization output may be used as a measurement of fitness, because it requires energy, or because high song output is correlated with high testosterone, which depressed the immune system (indicating a good immune system in birds that sing a lot). Does the structure imply something about the male's willingness to focus on a single female--implying a focus on a single clutch?
As a person person who has sung "Can you feel the love tonight" to someone unsuspecting in the cold, I can confirm, mixed results...
DeletePerhaps the songs are reflective of mental quality of the male finch for the female finches. The finches who can remember more songs, and songs of better quality, because they are capable of more complex actions, may be better at foraging or defending territory.