The final day before leaving Arenal, Katie and I went for a morning run. As I was cresting the final hill I heard an amazing bird call. I followed the sound up to the top of the hill where I found a 70 foot tree standing alone in a large cattle pasture, and from it was hanging a colony of woven nests. After hearing their call and watching them for a bit, I ran to get Katie, and then we ran to get the rest of the family.
Now, I had been hoping to see the Montezuma Oropendola for some time, because it is a crazy looking bird. But that was all I knew. I really had no idea how amazing and crazy the bird really is.
As I stood there, I watched the flurry of activity surrounding the Oropendola colony. Birds were flying in and out, birds were adding to and building the nests, and the calls came non-stop. After a minute or so, it began to become more clear how it worked. The females appeared to be smaller than the males. The females appeared to be the ones who built and maintained the elaborate hanging nests, and the males sit on nearby branches. As the sun began to set over the hills the nests were lit with a warm golden light, and I began to figure out what was going on. The females would fly from the nest to distant fields and return with beaks full of straw for the nest:
The next day, after we checked out from the hotel, we all drove back to the Oropendola colony so that we could all see it one more time.
As the females return from the field with straw the males call to impress them. Usually at least or more males would compete for each female that returned. Clearly they were competing for the attention of and mating opportunities with the females. The call of the males is a truly crazy thing. The sound is hard to describe already (see the video below), but what really makes the call special is that the bird flips upside down on the branch and spreads it’s wings when it does the call, in a really absurd and fascinating display. The females fly to the nest to add the straw, and sometimes a male will also fly down to the nest, and land on the outside and beat their wings violently about the nest. I couldn’t figure out what this was about, though. Perhaps just another display of prowess, perhaps these were males trying to damage the nest of competitors. Unclear.
Regardless, here’s a sample of the whole Montezuma Oropendola scene we saw that day. These birds shot to the top of many of our favorite birds of Costra Rica lists, which, we had to discuss at length in the car ride that followed.
Do run the video in HD (1080p), and full screen.