We were just summoned out of our camper for neighbors in the caravan park had pried an injured lorikeet from the front grill of an incoming car and they needed help. Lorikeets are small, rainbow colored parrots with very hooked and powerful beaks as Sara found out as she tried to catch it as it madly hopped across the lawn. Finally, she bagged it with a tee-shirt and we got it into a cardboard box so that a local WIRES contact could take it away to the wild animal hospital!
This morning, I had to go shopping and when I got out of the car at a car park a woman looked over and said, are you the bowerbird guy? She had seen the decal on the car door, but had obviously heard about us from someone we had met three years ago! So we traded contacts and learned about a bird watching club or two that may be able to help us in our work.
Then last week, another neighbor at the caravan park brought us two exhausted muttonbirds (a type of shearwater) both captured with wet and sandy towels from the foaming surf at high tide. It is muttonbird migration and many wash up dead on the beaches. The two she brought us didn’t survive despite a bit of fresh water and some tuna from a can. She picked us out as likely targets for she had seen us bird watching in the park during the last day or two. I guess we are getting ourselves and work known around these parts which is kind of neat.
Over the last few days since my last post we have been scouting for bowerbird bowers and testing some bowerbird methodology for simple behavioral experimentation. I have focused on what I call my bowerbird machine. It is a device that presents two decorations to a bowerbird and when he takes them, one at a time, I can later determine which one he took first. Currently, I am testing to see if a bowerbird can determine a difference between a piece of cardboard and a similarly sized magnet, both wrapped in blue tape. My hypothesis is that he will prefer the blue magnet, take it first, and place it in a more prominent position on his bowerbird mat. Time will tell if the data support this hypothesis.
One aspect of the project that is especially appealing is the evolution of the design of my machine. It needs to be made of natural materials, be super easy to construct (for we may do a workshop and have school kids build their own machines), and not offensive to a bowerbird. At an earlier stage in the evolution of the machine, I tried to make it as small as possible and blend in with the bowerbird’s straw that he builds his mat from. So it was fabricated from a few bamboo skewers, a bit of hot glue, and some cardboard from a cereal box! That was a disaster for no matter how carefully I tried to hide it, the bowerbird would just grab it with his beak and rip it out of the ground, tossing it several feet to the side!
In the next phase I decided it should be made of thin bark from a eucalyptus tree and designed to be just another natural artifact of living in the bush. I didn’t try to hide it. Eucalyptus bark from certain species constantly falls off and litters the ground. It is about as thick as regular wood veneer that you’d buy for furniture projects and perfect for my machine. Let me briefly explain how the machine works. The bark is cut to about 8 inches long and 3 inches wide. I glue cloth to the inside with regular white glue and let it dry in the shape of half a cylinder. Then I cut a 5 inch slot down the middle that is about as wide as a pipe cleaner. At one end of the slot I make it bigger such that a typical colored bead for making a cheap necklace will drop through. Then a small cardboard box, slightly wider than the bead and a half inch longer than the slot, and about an inch deep, is glued to the underside of the bark. If you are following me along, from the top if you looked into the slot you’d be staring into the inside of the box.
Ok. Now sticks are glued to the bark to hold it in a sloped position when positioned on the ground. The end of the slot with the large opening is positioned up hill. Check out the images. If you dropped a bead into the slot, it would roll down to the other end and stop.
Now how does this all relate to the two decorations that I am hoping Mr. Bowerbird will take? Each decoration, on its underside, has a piece of a pipe cleaner about half an inch long glued to it and protruding straight down. A colored bead is slipped onto the pipe cleaner, blue bead for the magnetic decoration and pink bead for the cardboard decoration. Carefully, the bead on the decoration is slipped through the large hole in the slot and the entire decoration is slid a bit down the slot to a resting place. Same treatment for the other decoration. When the bowerbird steals a decoration, the bead cannot fit through the slot, it pops off the pipe cleaner, rolls down the box to the end and stops. The bead from the second decoration will back up against the bead of the first decoration and by looking in the slot and noting the order of the colored beads one can determine which decoration was chosen first!
Scientists think that birds can see the magnetic field lines created by the earth and that they might even look blue. It is well known that birds use these field lines to help them navigate during migrations. Since the satin bowerbird orients his bower in a northerly direction it is possible that he uses these field lines to help him in the construction. He could also be using cues from the path of the sun across the sky but that is an entirely different topic which I won’t get into right now! My point is that since he prefers blue decorations, and that field lines may also look blue, a blue decoration with a magnet inside might be the ultimate decoration for his mat. And that may be how a bowerbird gets the “girls”! Stay tuned.