A white-winged dove recently decided that the hanging plant, sitting about head high a few steps from my front door, was just the right spot for a nest. At first this led to a frightening explosion of feathered wings every time a member of my family walked out of the door, but after a while the bird’s trust in us began to grow and it now refuses to leave for any reason at all.
While a bird nesting on our porch is a nice event for my little family, I didn’t consider it a topic for a wildlife article. That is, until I started drafting a piece on holes in trees and I realized that the dove in the plant and a hole in a tree were unexpectedly linked in a manner related to cost benefit analysis.
Before the dove decided to take up residence, the plant in the hanging basket was full and healthy. After a couple of weeks with its new avian tenant the plant has taken a beating. All of the leaves have been pushed to the side, and it just looks a little worse for wear. But on the plus side, the dove is pooping in the plant. From whenever my wife stuck it in that pot until now, the only nutrients the plant had available to it were in that fixed amount of soil. Now, its soil is being supplemented with a steady supply of bird fertilizer. Perhaps the structural damage the plant is experiencing by hosting the bird is worth the gain in soil nutrition.
The same thing is happening with a tree with a big hole in its trunk. One would think that having a big hole at the base of a tree is pure bad news. A tree without a solid core must be more likely to be toppled in the strong winds of a future storm than one with an intact trunk. There is some good news for the tree. I can tell you from experience that a tree cavity acts like a magnet for wildlife and a lot of that wildlife is pooping a bunch of nutrients directly above the roots of the tree. The idea that a tree with a hollow portion may benefit from an increase in nutrients due to wildlife isn’t my own, Daniel Janzen published a note in a scientific journal about it years ago.
Janzen’s idea has repeatedly popped up in my head over the years as I’ve had opportunities to point the lens of a camera trap at a hole in the base of a big tree. Tree cavities are fantastic locations for recording wildlife. I’ve recorded a wide variety of species in their vicinity. Some animals seem like they just can’t resist popping their head in to have a look around. Others will spend a few hours taking a nap inside. For the tree to get the benefits of increased nutrients in its soil, the species that really count are the ones using the tree hole as a toilet. Most of the time, the animals that are depositing a lot of scat are one species of bat or another. I’ve also found that a group of ocelots will sometimes use a tree hole as a communal bathroom, which in theory would provide the tree with an opportunity to grab whatever nutrients might be in ocelot poop.
Is the currently squashed hanging plant ultimately benefiting from the dove’s fertilizer? Does all of the scat deposited in a tree cavity outweigh the risk of being blown over? Who knows? What I do know is that it’s interesting to consider. I also know that it’s always fun to review a camera trap that’s monitoring a tree cavity because it consistently provides very cool videos, some of which you can see below.
About the Author
Vincent Losasso, founder of Guanacaste Wildlife Monitoring, is a biologist who works with camera traps throughout Costa Rica
