Female ospreys typically lay three eggs per season. Normally all of those chicks, or two of them, will hatch and survive long enough to grow up and leave the nest. But this year, in Connecticut, that rate was closer to just one bird per nest.
That’s according to a new study from the Connecticut Audubon Society.
It’s not the first time the rate has been closer to one bird per year, but it is the lowest since records began 12 years ago.
“It's not like a dramatic die off, but it's enough for us to be concerned,” said Milan Bull, the organization’s senior director of science and conservation.
Young ospreys struggle with lack of fish and extreme heat
Volunteers who monitored the birds from March to September reported anecdotal cases of starvation, possibly due to a decline in menhaden, a type of herring that osprey eat.
The fish are migratory, moving between Florida and Nova Scotia, and are often found in huge schools right when young ospreys are hungry, according to Bull.
“By the time the young need the most food, the menhaden are packed up along our shoreline, so there's a lot of food available,” Bull said.
But fewer adult menhaden have been found in Connecticut’s waters, due to possible overfishing in the Chesapeake Bay.
“The adult menhaden population in Long Island Sound has been decreasing for years and this year we had very, very few reports of any adult menhaden in Long Island Sound,” Bull said.
Osprey will eat juvenile menhaden, known as “peanut bunker,” if they can find them, but they don’t provide the same amount of nutrients and calories as adult menhaden.
“They’re the little tiny ones, about three or four inches,” Bull said. “Even if it takes three or four juvenile fish to equal the weight of an adult, those three or four still don't have the caloric content of the adult fish.”
A four-day heat wave in June when young ospreys normally start to hatch was another cause of death, according to the report. If the chicks were eating smaller fish than normal, they would have been more likely to die from heat exposure or malnutrition. On top of that, adult ospreys might have spent more time in the nest protecting their young from the heat than looking for food.
“If the adults have to spend more time shielding the young from the hot sun than they do recruiting fish back to the nest, then that would lead to starvation,” Bull said.
A new study: mounting cameras to osprey nests
Despite the dip in ospreys leaving the nest, there’s still enough to sustain the population in Connecticut. According to the report, 862 fledglings left the nest this year, which is more than double the number of fledglings flying away 10 years ago.
The Connecticut Audubon Society hopes to conduct a study next year that would involve mounting cameras onto nests to see how many fish adult ospreys are able to catch and bring back to the nest.
“The goal will be to determine which fish species the state’s ospreys eat, how many they eat, and how big those fish are,” according to the study.
“If over time the number and kind of forage fish change, it could indicate environmental problems that might affect not just ospreys but the region as a whole,” according to the study.
“We’re trying to get ahead of the game, basically, is what we’re trying to do,” Bull said.
Áine Pennello is a Report for America corps member, covering the environment and climate change for Connecticut Public
