Paulie and Chaos may have been the first penguins to produce an egg at the Tennessee Aquarium, but now the macaroni pair have company. Two pairs of gentoos are tending eggs of their own and there should be another egg by the end of this week.

"Gentoo penguins will keep both of their eggs in the nest as long as there is enough food and there aren't many predators," said Tennessee Aquarium senior aviculturist Amy Graves.

Ms. Graves discovered the first gentoo egg in "Bug" and "Big T's" nest on Saturday and a second egg was found Tuesday morning. If their eggs are fertile, Bug and Big T could be first-time parents. They are both five-year-old penguins that seem to be a bit free-spirited.

"All of the other penguins have been building nests since we first gave them rocks in April, except Bug and Big T," said Ms. Graves. "They had been observed courting and mating, but didn't build a nest until the last minute. They waited almost until Bug was ready to lay the egg."

The tardy nest building may be the result of inexperienced parents, but Graves said both birds are displaying parental instincts by staying on their eggs and being very protective of them.

Another new egg was discovered on Monday in "Biscuit" and "Blue's" nest. This discovery was not as big of a surprise as the other eggs. "Biscuit and Blue are the only penguins that came to us as a pair," said Ms. Graves. "They are both 15 years old and have had chicks together at SeaWorld."

While this pair appears to be tending to their first egg right now, Ms. Graves noticed the egg is dented. While a second egg will likely follow, their parental track record is somewhat in question. Biscuit and Blue have had eggs together for nine seasons in a row prior to arriving in Chattanooga, but they have only hatched three penguin chicks.

"Records show the parents didn't stay on the eggs for some reason," Ms. Graves said. "It could be that they lost interest in the eggs or that the other birds in the colony pestered them too much."

Although the parental instinct of this pair remains in question, there's not much doubt that at least one more egg should be on the way. Gentoo penguins normally have a clutch of two eggs which are laid approximately four days apart from one another.

"We're also watching the gentoo pair "Poncho" and "Peep" as they could still lay some eggs," said Aquarium aviculturist Loribeth Aldrich. "But the macaroni courtship behavior appears to be winding down."

The incubation period for macaroni penguins takes 33 and 39 days. So if Chaos and Paulie's egg is fertile, a chick could begin to "pip" or hatch between June 15 and June 23.

The incubation period for gentoo penguins takes 36 to 41 days. So keepers will have to wait until sometime in mid-July to see if the newly discovered gentoo eggs are fertile.

While these new developments have generated plenty of excitement, experts point to Biscuit and Blue's track record as reason not to count any penguins before they hatch. "Whether in the wild or on exhibit penguin chicks must overcome many hurdles to reach full maturity," said Dave Collins, the Aquarium's curator of forests.

In the meantime, Aquarium visitors will have plenty to see as these couples tend to their eggs, each other and occasionally squabble with the other penguins. "It's really fun and interesting to watch their behavior and how they interact with one another," Ms. Graves said.