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• Tiger sharks gather around Hawaii’s French Frigate Shoals in summer to prey on newly fledged seabirds, a new study has revealed.
• The influx of tiger sharks pushes smaller shark species to change where and how they hunt.
• Seasonal seabird movements strongly influence the balance of the entire local shark ecosystem.

When seabirds fledge, northwestern Hawaii shark ecosystems are disrupted

There are several shark species that patrol the waters of the French Frigate Shoals atoll in northwestern Hawaii. In December 2025, scientists reported that the population of tiger sharks surges during the summer in some areas of the atoll. That’s because those sharks are opportunistically preying on newly fledged seabirds, primarily albatross chicks. Moreover, that high seasonal influx of tiger sharks forces smaller sharks in those waters to change the way they use their habitat.

Chloé Blandino, at the Hawaii Institute of Marine Biology Shark Lab, is the lead author of the paper on this study. She said in a statement:

We discovered that tiger sharks gather around small islands in summer to hunt fledgling seabirds, which, in turn, forces other smaller sharks to adjust their habitat use. It’s a clear example of how a seasonal food source can influence habitat use by an entire predator community.

The researchers published their findings in the peer-reviewed journal Ecosphere on December 2, 2025.

Tiger sharks go after young seabirds

The French Frigate Shoals in northwestern Hawaii is a crescent-shaped barrier reef with small sandy islands. These tiny islands provide critical habitat for seabirds, green sea turtles, and Hawaiian monk seals. The seabirds include species like albatrosses, tropicbirds and terns.

During the summer, tiger sharks converge in the atoll waters to prey on fledgling seabirds. These young birds, which hatched just months earlier, are just learning to fly. As a result, they have not yet become adept at avoiding predators.

Tracking shark behavior

The researchers targeted three species known to frequent the atoll waters: tiger sharks (Galeocerdo cuvier), Galapagos sharks (Carcharhinus galapagensis), and gray reef sharks (Carcharhinus amblyrhynchos).

They surgically inserted acoustic transmitters in the sharks, each one emitting a unique coded signal. Their work followed careful animal handling protocols that University of Hawaii researchers developed to minimize harm to the sharks.

In addition, the researchers installed underwater receivers to pick up sounds from each shark’s transmitter. These receivers were placed in habitats occupied by the sharks: near coral reefs, as well as in deep and shallow lagoon areas. As a result, when a shark swam near a receiver, the signal from its transmitter was picked up, recording a timestamped location for the animal. This allowed the scientists to track each shark’s movement.

Extra influx of tiger sharks affects other sharks

For two years, the scientists tracked 128 sharks at the French Frigate Shoals. Their data revealed interesting information about the sharks’ movements.

They found that tiger sharks are more abundant in the shallow lagoon of the atoll in summer, around the time that albatross chicks are fledging. They were taking advantage of easy prey since the chicks were not yet adept fliers.

Moreover, the summer influx of tiger sharks also affected the dynamics of the atoll’s shark community. Grey reef sharks, which are smaller than tiger sharks, moved out of the lagoon areas occupied by tiger sharks. They retreated to waters near the reef to primarily hunt fish. Meanwhile, Galapagos sharks changed the timing of their hunts in some places. They also preyed on monk seal pups, avoiding albatross chicks.

Towards the end of summer, surviving fledgling seabirds, along with their parents, dispersed farther out to sea. With no more easy prey to take down, most tiger sharks moved out of the shallow lagoon, and the other sharks returned to their usual ecological niches.

Seabirds have a big impact on shark population

Carl Meyer, also at the Hawaii Institute of Marine Biology Shark Lab, is a paper co-author. He and his colleagues noted that if the birds lost their habitat to adverse weather, it would have a significant effect on the shark community, the Hawaiian monk seals, and of course, the seabirds themselves.

Meyer commented:

This study highlights the far-reaching impact of seabirds, showing they can shape the movements of top predators like tiger sharks, which then ripple through the entire food web. Understanding these predator-prey links is crucial for managing Hawaii’s marine ecosystems.

Bottom line: When seabirds fledge at the French Frigate Shoals atoll of northwestern Hawaii, tiger sharks move in to prey on the fledgling seabirds, disrupting shark populations in the area.

Source: Seabirds mediate intraguild and competitive interactions in a shark community

Via University of Hawaii Manoa

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