A fish was caught on camera attacking and eating a baby bird

Birds have often been seen swooping down into the water to grab fish for dinner. But now a scientist in Georgia has captured first-of-its-kind footage of a fish chowing down on a bird still in its nest. 

In 2019, Corina Newsome was studying nest predation in salt marshes with mammals in mind. Her team set up video cameras on seaside sparrow nests in Brunswick, Ga. 

One of the nests, which had a freshly-hatched chick, flooded with tide water. What happened next was a real "plot twist," she said. 

"When the water filled the nest, a mummichog, which is a small fish that lives in tidal marsh environments, leapt into the nest from the surrounding water," Newsome told As It Happens host Carol Off. 

"[The fish] kind of hung out in the nest for a second and then grabbed the chick  — that was still alive — by the leg and started thrashing it around underwater, eating little bits of the chick in the process."

The act of predation was documented and published this month in the Wilson Journal of Ornithology.

The marshes in Georgia lay low along the edges of lakes and streams. In Brunswick, they are surrounded by grass, which provides cover for the sparrow's nests. 

Newsome says the seaside sparrows are fully adapted to life in the coastal salt marsh and can spend their entire lives there. But there are times when predators can still find their nests.

"Understanding this threat of nest predation and kind of how it varies across the salt marsh is really where my research comes in," she said. 

Her research also shows that predators are not the only threat to these sparrows. Living in the marsh exposes them to flooding in wet seasons or at high tide. High tides occur twice a day in the coastal salt marsh she studied.

"[The chick] was already at a risk of drowning. It had not drowned yet by the time the fish had entered the nest. It is possible for chicks to survive a nest flooding event ... if they can keep their nostrils above the water while the water is in the nest," she said.

"But because the fish came in and dragged the chick underwater, eating it, the chick was not able to survive."

Newsome says the unexpected interaction shows the birds face predation threats close to the ground. Sparrows have to be cautious of the mummichog as well as the terrestrial predators roaming above. 

Threats of climate change

While the video shows the mummichog eating the chick, more research will be needed to see how often this occurs in the salt marsh. 

For starters, the mummichog would need help from the waters to reach the nest.

"We know that nest flooding is projected to happen more frequently because the level of the sea is rising and high tides are getting higher," Newsome said.

But scientists are also looking at the marshes and their abilities to adapt and grow.

"Sea level rise is also going to simply shrink the available marsh that's there for seaside sparrows to live and nest in.
 Newsome said. 

Marshes tend to gradually move inland onto formerly dry land as sea levels rise. This migration can convert forests into marshes, Newsome said.

"The big concern is that because sea level rise is happening so fast, the marsh will not be able to migrate and create space for these birds to nest in," she said. "That's actually one of the more urgent threats."

The scientist says her research aims to get people to intervene and protect the birds.

"While wildlife managers can't necessarily stop sea level rise, we can respond to nest predation," she said. 

In the case of the seaside sparrows, Newsome suggests pinpointing where the threat of nest predation is highest for terrestrial predators. Wildlife managers can then exclude those predators from those areas and make the sparrows less vulnerable.

It is just one of many techniques, but she says that by countering higher level threats, more nests can be elevated and avoid nest flooding.

Written by Mehek Mazhar. Interview produced by Chloe Shantz-Hilkes