Delicate Nests: Breeding the Purple-collared Woodstar

Abstract

M any bird enthusiasts have long been fascinated by the diminutive and pugnacious hummingbird. Most people associate these miracles of the bird world with the lush, equatorial tropics or springtime blossoms in city parks. There are a number of hummingbirds, however, that occupy a different ecological niche: high elevations of the Andean mountains in Ecuador and Peru.

As a consequence of their geographical location, little is known of the natural history and breeding biology of these mountain hummingbirds. One representative species of this group is the Purple-collared Woodstar Myrtis fanny. It is known that woodstars forage for the nectar and insects found in and around the montane blooms. They also migrate between lower and higher altitudes to find available nectar in the ever-changing environment of their mountainous habitat.

The Purple-collared Woodstar is one of the smallest hummingbirds, weighing 2.5 to 3 grams and measuring about two inches in length. Males and females are largely the same in coloration except during breeding, when the male develops turquoise coloration at the throat with a purplish band at the base, the "collar" that gives these birds their common name.

In 1991, the Zoological Society acquired two pairs of Purple-collared Woodstars, which were introduced to the Zoo's Hummingbird Aviary. Because so little is known of this species in the wild, we hoped to obse~e and record the breeding behavior of our birds. One of the first things. we learned was their courtship behaviors. Each hummingbird species seems to have unique courtship rituals. We observed the male Purple-collared Woodstar performing two kinds of courtship flights. One is reminiscent of a helicopter: the male hovers directly over the perching female at a height of about three feet, then lowers himself in the same hovering fashion until he is only inches above her. In the other, the male hovers directly facing the perched female, only inches from her beak, and sways and rocks back and forth. This last behavior has also been observed toward other hummingbirds of both sexes, suggesting it may have an aggressive or territorial meaning at other times.

We also observed that Purple-collared Woodstars exhibit the typical breeding patterns of other hummingbirds: the male only participates in courtship and copulation, and the female is solely responsible for all other duties, including nest building. Our birds made several nesting attempts. We provided abundant supplies of nesting material, such as cotton, shed hair from horses, dogs, and hoofstock in the collection, seed pods from the silk floss plant, and spiderwebs that we twirled onto sticks. We placed these randomly throughout the aviary.

The females seemed to routinely build nests near high traffic areas in the aviary. The nests were about l 1/2 inches in diameter, 1 inch tall, and 1/2 inch deep, and they were made primarily of cotton, with horsehair and tiny threads woven in, bound together with spiderwebs. Tiny pieces of feathers, moss, and leaves were the finishing touches, camouflaging the exterior surface of the nest. The nests were built on the tines of bamboo palms (chamaedorea sp.), the runners of spider plants (chlorophytum sp.), and in a tababouia tree. The female spent six to 10 days constructing the nest, then sat on the nest for a period of up to three days before laying two eggs, each less than one-half inch long.

We discovered that the male continued his courtship during the nestbuilding and egg-laying process. The females also seemed to nest whether the males displayed breeding plumage or not. It may be that fertilization of the eggs is dependent upon the males being in full breeding plumage--all eggs laid while the males were not in full coloration turned out to be infertile. We had several infertile clutches in the aviary.

But in June 1993, a female was observed building a nest in a bamboo palm, and a male in full coloration was seen "helicoptering" over her most of the day. The female chased him off repeatedly to resume her nest building. Eight days later, she was sitting on the nest, although it did not look complete. She bound it with spiderwebs and camouflaged it the next day, while the male continued to display. Two days later, the first egg was observed, and the female remained sitting on the nest all day.

Another egg was also laid, presumably one or two days later. In this species, incubation appears to begin after both eggs are laid and, for our birds, lasts 19 days.

That 19th day turned out to be a day of surprises. Upon entering the aviary in the morning, we discovered that the nest had been disrupted--the palm frond the nest was attached to had broken, and the nest was empty! We searched the ground for the eggs, but instead we found a newly hatched chick cradled in a leaf directly below the nest. We never found the second chick or egg. The surviving chick was cold but alive, so we placed it temporarily in a warm brooder box.

The nest itself turned out to be intact, so we decided to try and remedy the...

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References

Dunning, John S. (1982). South American Land Birds. A photographic aid to identification. Newton Square, PA, Harrowood Books.

Gould, john. (1990). John Gould's Hummingbirds. Secaucus, NJ, Wellfleet Press.

Greenwalt, Crawford H. (1990). Hummingbirds. New York, NY, Dover Publications, Inc.