By: Kate Ruskin @UMaine
People often cite birds as the ultimate example of romantic faithfulness (see Never Been Kissed for an incorrect, but nonetheless romantic, usage: “You know, Adelie penguins, they spend their whole lives looking for that one other penguin and when they meet them, they know. And they spend the rest of their lives together.”). The fact is birds exhibit an incredibly diverse array of mating systems: monogamy, social monogamy with cheating, one male with multiple females (polygyny), one female with multiple males (polyandry), and in the case of Saltmarsh Sparrows, complete promiscuity.
The BBC Earth News named Saltmarsh Sparrows the world’s most promiscuous bird species based on a study by SHARP members and collaborators (BBC Article and SHARP study). I’ve been thinking about this study a great deal lately, as I’ve been using the genetic data we collected from nesting females and their chicks to calculate the number of sires for each nest. Below’s a screenshot of the results for one family—all five of the chicks have a different father!
Not the most traditional love story or family model, but it works for Saltmarsh Sparrows.