Breeding and Rearing the Guir a Cuckoo rGuiaA GuiaAJ at the Houston Zoo

Abstract

of the broad order uculiformes, Guira Cuckoos

Guira guira) are grouped with three species of Anis in the subfamily Crotophaginae, and they alone make up the monotypic genus Guira. Although these quirky cuckoos are grouped with the Anis, their social system and breeding habits in the wild differ. Ani species and the Guiras are group nesters; however, the Anis tend to form monogamous pairs within their breeding group, with the monogamous pairs laying in a communal nest. While the Guiras use a communal nest, they do not form monogamous pairs, but practice polyandry and polygyny within the group (Quinn et al. 1994). They are common in their native habitat in East-central South America, and tend to prefer scrub and second growth forests, but also inhabit grasslands where they forage together in groups for insects and other small animals (Hoya et al. 1997).

Groups can be as large as 25 in the dry season, but breeding groups are usually less than 15 birds. Guira Cuckoos rarely nest as pairs (Macedo 2002). Both sexes participate in territory defense, nest building, incubation, and rearing of the young. As many as 20 eggs have been found in one communal nest; however, average clutch size is 10 and tends to vary with group size (Hoya et al. 1997). Larger groups lay more eggs, but do not raise more young, as more eggs and chicks are removed by group members (Hoya et al. 1997). The eggs are pale blue turquoise with white calcareous patterns overlaying the blue. Hoya et al. (1997) suggested that these white markings may help each hen differentiate her eggs from other hens' eggs, and ensure that any egg she removes will not be her egg. However, Cariello et al. (2004) found through DNA testing that eggs with similar characteristics such as weight, length, size,

shape, and markings, were not from the same hen. It is common for group members to remove some or all the eggs from a clutch and kill very young nestlings (Macedo 2002, Macedo and Melo 1999, Quinn et al. 1994). It is thought that this is done to trigger another breeding attempt, and to increase the chance that all group members are represented in the breeding attempt.

Chicks hatch well-developed, covered with cream colored hair-like feathers, and have pink mouths with pairs of white papillae on the roof of their mouths and around the tongue (Hoya et al. 1997). The nestlings are seldom full siblings, and are usually half siblings, or unrelated (Quinn et al. 1994 ). In addition to facing infanticide from their group members, chicks may also be killed by their nest-mates (Hoya et al. 1997). Macedo (2002) found that 42 percent of eggs were lost due to ejection from the nest, and 50 percent of chicks died from infanticide. Hoya et al. (1997) notes that only 26 percent of eggs and 55 percent of chicks survive to fledge. Nestlings become highly mobile in the nest after day three (Macedo 2002) and normally fledge around day 12-15, but may leave the nest at day five or six if disturbed (Hoya et al. 1997, Macedo 2002). The birds usually nest only once, rarely twice a season (Macedo and Bianchi 1997). While much is known about their life in the wild, not much is written about their activity in captivity.

Houston Zoo Husbandry

The Houston Zoo started working with Guira Cuckoos in 1997, and had its first successful breeding in 2002. The Zoo has had success breeding Guira Cuckoos in a small group of two males and two females, one male and two females, and most recently, two males and one female. We have found that with these smaller groups, fewer eggs are tossed out of the nest, and very few nestlings are killed. The group of four was the first to hatch and raise their entire clutch of five eggs to fledging with minimal 

keeper intervention. One of the females died of egg binding about 10 days after this clutch fledged. This bird appeared to be the dominant female, doing the majority of feeding and nest attendance. However, the remaining trio of adult cuckoos continued breeding and raised all but one of their chicks to fledge.

The Guira Cuckoos are housed outdoors in a mixed species exhibit and have access to a covered night shelter for inclement weather. They have bred successfully in two similar exhibits, Exhibit A: 7.6m x 8.3m x 4.5m and Exhibit B: 6.1m x 6.1m x 6.1m. The exhibits are covered with 5- 7 cm of blasting sand; each has a pool, and is planted with various trees, shrubs, and grasses. Extra perching is added as well.

Nest baskets were provided for the cuckoos and placed at various heights from 1.5m to 4m. It was soon determined that the birds preferring the higher baskets. Cone-shaped wire nest baskets measuring 25cm in diameter by 15cm deep (typically used as hanging planters), were lined with

Enka mat before being hung inside the exhibit. Nests were usually available throughout the year, as lack of a nest did not discourage the birds from laying eggs. On two occasions, they tried to build their own nests, but the structure was not sufficient and the eggs fell through. Hay was provided, but the birds added feathers, sticks, grasses, and leaves to the nest.

Shortly after lining the nest with fresh leaves, the birds began to lay their eggs. Depending on the number of females per group, our cuckoos laid 3 to 9 eggs per clutch, and would re-clutch after either a failed attempt or a successful nesting period. We have had as many as three successful nests in a year. Holding availability, exhibit space, and demand by other institutions helped determine if the birds would be allowed to raise offspring. If the clutch was not wanted, the eggs were pulled and replaced with dummies. The birds sat readily on their dummy clutches. Some clutches were candled just prior to their hatch date, and dead or infertile eggs were removed. With most clutches, any eggs remaining three days after the others hatched were candled, and dead or infertile eggs were 

removed. All removed eggs were included in analysis. On one occasion, a nest with young chicks was lowered from 4m to 1.5m to facilitate supplemental feedings. The adults eventually resumed care after three days of hand feeding in the nest, once the chicks had regained their strength.