Background
The ability of males to sing local song types can be an important factor in determining a male reproductive success. Our lab has further shown that during aggressive interactions, song sparrows use song types shared with neighbors in complex ways to communicate levels of aggression and intent to attack. Song sharing is therefore an important and often overlooked behavior in many species.
The purpose of this model is to test specific hypotheses about cultural transmission of a particular behavior: the sharing of distinctive song types among neighboring birds. I am also interested in testing hypotheses about how complex patterns of song sharing have arisen in the bird neighborhoods within our study populations.
What the model explores
Environment
- Habitat patchiness, often caused by human disturbance, can decrease the number of song tutors a young bird has to learn from.
- Habitat structure can also determine who birds learn from. Barriers to movement, such as open fields for species who prefer wooded areas, can create complex patterns of song sharing at the local level.
- Mortality rates vary with geographic location, capacity of habitat to sustain individuals, predator densities, bird age, and other factors. Does mortality rate affect what songs a bird learns, and how many neighbors it has?
Behavioral strategies
- Timing of dispersal is a crucial event for young birds, and can have a direct effect on how many songs they share with their territorial neighbors. If birds leave their natal area after they have memorized their songs, they will likely not share song types with any neighboring birds. Likewise, if birds can learn later in life, they can drop songs that are different from those in the area where they settled and add local song types.
- Song learning strategies have a direct impact on sharing. If birds prefer to learn shared songs, then song sharing should generally increase in the population. However, birds may use other learning strategies, such as learning from the most successful male, learning from as many neighbors as possible, or randomly selecting songs. Without a model, it is hard to predict the effects of these strategies on sharing.
Existing cultural conditions
The songs that already exist in a neighborhood are the only material, besides improvisation, that young birds have for their own song learning. This recursive connection to previous generations can create complex patterns of sharing that, in turn, affect successive generations and can only be seen in a generational model such as this one.
The program
Sim Songbird simulates the song dynamics of a neighborhood of songbirds over time. Simulated birds hatch, disperse, memorize songs from tutor birds, select their repertoire, establish territories, and tutor new birds. Important variables such as when birds learn, who they learn from, and environmental factors are adjustable as parameters. Over years, a pattern of song sharing develops that can be compared with real bird populations.
The screen picture below is from the model in its current state of development. Although not complete, the model still generates patterns of song sharing that look like natural conditions and can be manipulated by changing parameters.
