2004 Bridges Summer Research Report Christopher Clark Integrative Biology "Effects of elongated tails on maneuverability in hummingbirds"

Introduction

I study how hummingbirds use their tails. Hummingbirds as a family have a diverse array of tail shapes, and many species have strikingly elongated tails. In many of these cases, males have elongated or otherwise modified tails and females have relatively “normal” tail shapes, indicating that these modified tails probably serve to help the males obtain mates. As a consequence, I predict that an elongated tail imposes a performance cost on the birds that bear them. Birds appear to use their tails to assist them while maneuvering, so the purpose of this project is to assess the effect an elongated tail has on hummingbirds’ ability to turn.

My experimental setup in the basement of the Windsor Research Station. The two high-speed cameras (red handles, center) are pointed at a portion of my flight arena. The cameras record at 500 frames per second, allowing me to see how the wings and tails of the hummingbirds move as the birds maneuver in my arena. To the left is a table showing some of the equipment I have for catching, measuring and feeding hummingbirds. Some of my food is present, too.

Males of the Jamaican Streamertail Hummingbird variety (Trochilus polytmus) have one of the longest tails of hummingbirds. I traveled to Jamaica to catch males and females of this species, in order to test how the male’s elongated tail affects his ability to perform a maneuver.

Methods

Experimentally, my plan was to catch birds in the wild, and train them to feed from a feeder inside of a cage—my “flight arena.” My advisor has two portable high-speed cameras, so I brought these cameras with me and arranged them so that they obtained a bottom view and a side view of the area in front of the feeder. When birds flew to the feeder, I scared them and recorded the escape maneuver they performed to get away to the far end of the cage.

I first filmed males with their natural tail. Second, I trimmed the elongated tail-feathers off, and replaced them with a female’s feathers. (Feathers are dead when mature, just like hair; but unlike hair, they are hollow, making it easy to stick a pin inside to glue one feather onto another). Third, I put the male’s elongated streamers back on him, and fourth I plucked his entire tail. To females, I did the same thing, except that I attached a male’s streamers rather than a female’s.

Outcome of travel

On July 6 I flew to Mobay, and then to the Windsor Research Centre on July 7 (see photographs). My plan was to stay at Windsor for six weeks, catching Trochilus locally. However, for the next 17 days I failed to catch any adult male Trochilus. The species was present in the area; I saw several males and caught over a dozen females and juvenile males (which have no streamers). I saw adult males with streamers feeding on bromeliads in the tops of trees, however I was limited to catching birds that flew low to the ground.

A picture of the Windsor Research Station. It was built in the 1870s as a home for the overseer of the Windsor plantation.

Consequently, on July 24 I hired a taxi and drove to the far end of the island, to Hardwar gap in the Blue Mountains. There, I lived with a family of Rastafarians in a village of about 50 people. Trochilus were abundant there, and more to the point, I was able to catch a few males with streamers in addition to females. Unfortunately, the birds in this area were undergoing their annual molt so I could not use most of the birds that I caught for my main experiment. However, I did manage to get a sample size of 6 or 7 birds. Additionally, I was able to perform a side project on mechanical noise production in the birds, which I may be able to publish a note about in an ornithological journal.

A female red-billed streamertail in my flight arena. Note the long tail-feathers: these feathers are normally only found on male streamertails.

At present, I have not digitized the videos I collected in Jamaica. I expect that this will take quite a bit of the fall and spring to do.

Relationship of research to degree goals

Pending further discussions with my advisor, I believe that I need to collect more data for my main experiment described here. This experiment will constitute the majority of one chapter of my Ph.D. thesis, complementing the other chapters, which are on the variation in tail morphology in hummingbirds, the metabolic costs of tail elongation, and an unknown final chapter.

The Windsor Cave is less than 1 km from the Windsor Research Station. Dango-mar has been guiding tours in the cave for 30 years!

Millions of fruit-eating bats live in the cave. They bring fruit back with them to eat. The big seeds are discarded, and the little ones are defecated onto the floor of the cave. Bat guano is some of the best fertilizer in the world, but these plants are nonetheless doomed to die because there is no light!

Interesting rock formations in the cave

Jamaicans traditionally kill any snake they find, in spite of the fact that there are no poisonous snakes on the island, and the snakes eat prodigious numbers of rats. The Windsor Research Center pays a bounty for live Jamaican Boas, which they tag and release where the animal was found. This serves two purposes: to educate Jamaicans about snakes and conservation biology, and also to learn basic information about the snakes.

For part of my trip I rented a room from some Rasta coffee growers. Here we see Opie with a coffee roaster, a crate of still-smoking coffee that has just been roasted and the cooking fire in the background. The smell was extraordinary!

Here Opie is spreading the coffee out to cool and to pick through it for under or over-roasted beans.