Abstract
In April of 1974 Riverbanks Zoological Park acquired four Toco toucans-two from a bird dealer in Florida and two from a bird dealer in New Jersey; the sexes were unknown. After a routine quarantine period, all four were placed in an outdoor exhibit on the southern side of the birdhouse. The enclosure was shared with a pair of Crested seriemas. Exhibit dimen-. sions were roughly 1 Om wide x 3m deep x Sm high. Plant material used was entirely evergreen shrubs, and ample perching was provided by suspending heavy vines across heart cedar snags buried in the ground. The front of the exhibit was covered with 1 " x 2" welded wire fabric. Through a doorway at one end, access was provided to a "winter quarters" room measuring approximately 3m x 2m x Sm. This room was heated by electric cables buried in the concrete floor and perching consisted simply of two heavy dowels. Diet for the toucans consisted of diced fresh fruit. soaked raisins, and grapes coated with insectile mix and topped with bits of Zupreme Bird of Prey diet.
The toucans and seriemas coexisted well, showing very little interaction. No breeding behavior or pair bonding was noted in the toucans for the rest of 1974. In the spring of l 97S the seriemas did show an inclination to nest, and a platform was provided in the winter quarters room. By chance, a discarded "grandfather clock" type nest box was used to raise the platform off of the floor some 2 meters. The seriemas did in fact build a nest on this platform and subsequently laid a series of infertile eggs during the summer of 1975. The toucans still showed no breeding behavior until late October of 1975, when some aggression was noted towards one individual. By l November it was obvious that three of the four birds were openly antagonistic towards the fourth, and this bird was permanently removed from the exhibit. In December 1975 a Palmetto log (sabol palmetto) was mounted on the wall of the main exhibit opposite the winter quarters room door. An entrance hole was chiseled through the hardouter crust, but the pulpy interior of the log was left intact.
During the winter of 1976 the three remaining toucans continued to interact on an apparently equal basis. On 15 March one individual was seen excavating the nest Jog, and for the next several days all three toucans were observed daily working at the entrance. On the basis of mandible size it appeared now that we had one female and two males. By the end of March a true pair bond began to evolve between the female and the Alpha male. These two assumed all the excavation chores and defended the nest log area whenever the Beta male approached. Outside of the immediate nest area the Beta male was rarely attacked, and actually was involved in mutual preening with both of the pair. By 8 April the log had been excavated to the point that either bird could fit its entire body into the opening and disappear completely from view. Now an unexpected behavior began to occur-the female was repeatedly seen entering and emerging from the grandfather clock nest box. At the same time excavation of the log continued and on 20 April both the Alpha male and the female showed aggression towards the keeper servicing the exhibit. On 30 April pieces of egg shell were found on the main exhibit floor, but at this time the source was indefinite because the seriemas were once again nesting. On 4 May a broken egg was found inside the grandfather clock nest box, thus confirming our suspicions that the female toucan was in fact producing the eggs.