Study: South Jersey Osprey Chicks Are Dying at Alarming Rate

A new study led by a biology instructor at Stockton University found a staggering decline in the survival rate of osprey chicks over the past two years and an apparent reason for the loss -- not enough of the right food.

The osprey, the mascot of Stockton University, is a raptor that feeds primarily on fish.

Ospreys were reclassified from “threatened” to “stable” earlier this year by New Jersey’s Department of Environmental Protection’s Fish and Wildlife agency.

However, this Stockton University study and another last year by the Conserve Wildlife Foundation of New Jersey call that reclassification into question.

The Conserve Wildlife Foundation of New Jersey study points to the connection between the food supply and osprey productivity, specifically Atlantic menhaden or bunker.  

Stockton University's Study Monitoring South Jersey Osprey Nests

Melanie Schroer, an instructor of Biology at Stockton University, monitors 27 osprey nests along the Mullica River and Great Bay and has installed wildlife cameras on 10 of the nest platforms.

She also works with the Stockton Marine Field Station to bring students to the nesting platforms to monitor with a long selfie stick that can peek into nests to document egg and chick activity.  

In May, during the first nest survey, there were 54 eggs and three chicks. By the end of June, there were 25 chicks and one egg that was unlikely to hatch.

On July 17, there were 14 chicks. The final survey in August counted nine fledged chicks.   

The 85 percent loss of chicks for the nest sites this season is sounding an alarm.    

“The broader context here is that osprey nest productivity is declining. Nesting success has taken a huge hit, not only in my little part of the world, but also New Jersey, and much of the East Coast, and so, of course, everyone wants to figure out what's going on.

 

This population has been recovering for 50 years, and it's been doing great, and then just the last handful of years, not so much anymore,” she said.  

Lack of Osprey's Natural Food Source Likely the Reason for the Decline

Melanie Schroer says analysis of what adult ospreys are fishing for and what they are catching and feeding their young gives an important clue to figure out why the chicks are being found dead and emaciated.

Last year during nest monitoring, Schroer noticed a switch in diet.

“We saw that in the beginning of the season in May, they were bringing a lot of bunker back to the nests. But then by the end of May, early June, they switched to mostly flounder, which doesn't seem like a big deal, but flounder, when you think of calories per kilogram of fish, is less than half of a bunker. 

So they're putting in more work and bringing back fewer calories, fewer resources for their young,” she said.  

Schroer is also looking at how the chicks interact with each other.

Osprey Chicks Are Starving

“Osprey chicks generally take turns eating, and everything's okay, and they're docile, but when food is limited, generally the aggression increases. This is a way of maintaining a hierarchy within the nest. The oldest, biggest chick gets fed first, and therefore, it's the most likely to survive."

"We’re trying to look at chick aggression to confirm that not enough calories are being brought to the nest, and, yes, the chicks are actually experiencing stress and hunger. So even if we can't count the number of fish that are in the bay, you can still see the effects,” she said.  

Andrew Genovese, a Biology major from Egg Harbor Township, saw the aggression play out in nest cam footage. "Osprey chicks could often be seen pecking and biting at each other," he said.  

Genovese participated in last year's field surveys and recalled, "We'd find dead chicks present in or near a nest. That was usually a rarity, but sometime around halfway through the season we realized that the rate at which we saw them was abnormal." 

Going into this year's field season, he felt "unsure, but cautiously optimistic about what to expect in terms of population success" and hoped last year was an outlier. 

"By the end of the season, the tragically high 85 percent loss of chicks had completely disheartened me. It was painful to have spent so much time watching over them, noting observations, and seeing them grow only for so many of the nests to fail," he said.