The all-black fantails of southern New Zealand get replaced by all pied birds as you head north. This pattern is repeated in some other NZ birds, like the variable oystercatcher. As things get warmer, there are fewer advantages to being black.

Below is a graph of our results so far (as of 21 November 2014). (The spike at 42 degrees south just means we need more observations to get a more accurate estimate of the proportion of black to pied birds at that latitude.)

We're interested in getting heaps of observations of fantails including whether they were pied or black phase. This will allows us to better understand how the ratio of black to pied changes throughout New Zealand and how it shifts in landscapes with less forest and over time as New Zealand's climate continues to warm.

Feel free to add a comment here if you've got something to say about this project.