LOS ANGELES, CA (Catholic Online) - According to Thiago do Nascimento, a biologist at the Peruibe Aquarium, about 556 dead penguins have appeared on beaches since July 11.

Penguins are not an uncommon sight on Brazilian beaches, as they tend to show up during their migration. Most of the time, they are alive, and just use the area for a resting spot before continuing their flight, biologists say.

Necropsies performed on many of the penguins show that they had no food in their stomachs and probably starved to death, presupposing that the cold weather probably contributed to their deaths.

It's a strong possibility that the cold waters, brought on by a regional cold front, made the fish that the penguins eat seek warmer waters. Further tests are being conducted.

Penguin appearances and rescues have become common in recent years on the famous beaches of Rio de Janeiro.

It's normal for Magellan penguins to leave their colonies in the Antarctic in an annual migration in search of fish, following the plankton-rich, frigid water currents traveling north along the coast of South America. What has changed is that they are increasingly unable to return home because they get sick, weak or disoriented for reasons that have yet to be determined.

Biologists theorize that climate change, overfishing and pollution of the water all could contribute to the penguins becoming lost.

The Niteroi Zoo, near Rio de Janeiro, first began receiving penguins for rescue in 1999. Since then, they have received an increasing number of the birds, peaking with 1,000 penguins in 2008.