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Raising a Fish Hawk Family

Dedicated as osprey parents are, their chicks need luck — and good weather — to survive

      I am waiting. Every spring, I wait for my two osprey to return to their nest along Maryland Route 4 near Jug Bay Wetlands Sanctuary. I call them my osprey because I watch their progress on my commute home, and each year I note whether they are able to raise young. It is an interesting show with daily installments.
     This year, I also wait to see if the pair will be more successful than in 2018, when they didn’t manage to raise any young.
     The good news is that last year my osprey were unusual. After particularly poor rates for chicks in 2017, last year represented in an impressive rebound for local osprey. This was a great relief for wildlife biologists — and for me. 
    “Timing is everything,” says Greg Kearns, naturalist and environmental educator at Patuxent River Park.
     When the survival rate of osprey chicks dropped drastically in many Chesapeake locations in 2016 and 2017, biologist Bryan Watts at the Center for Conservation Biology proposed three likely factors: food shortage, predation by large raptors and the unusually cool, wet spring weather. Based on the rebound in 2018, it appears weather was the biggest factor.
     “The number-one killer is weather,” Kearns says. “2018 was actually a wet year overall, and it started bad. Then May had a lull until early June. That lull happened at a critical time for the osprey.”
     The critical time runs from hatching until the chicks are about three weeks old. In that period, young chicks are “super vulnerable” to hypothermia and respiratory ailments.
     The most prevalent respiratory ailment comes from a fungus called aspergillus, which thrives in cool, wet environments — like an osprey nest during spring rains. The chicks inhale fungal spores, which then infect their lungs. The fungus kills a lot of chicks. Kearns says that he checked three nests early last spring during the wet conditions and found that three chicks died within a single day. 
     The break the osprey got from the rain and cold was just long enough for the immune systems of newly hatched chicks to mature so that they could survive the fungus and also grow enough feathers to keep them warm when the rains returned. Many osprey parents that lost chicks in early wet weather also had enough time to re-nest and raise a second brood. 
     The result was a bumper crop of chicks. Last year Kearns counted 91 chicks from the nests he monitors in the middle Patuxent river and Jug Bay. This was a substantial increase over the numbers in 2016 and 2017. Across the Bay, Poplar Island, where Kearns also surveys chicks, saw a big jump, too. 
      The lower Patuxent River also did well, producing 227 chicks, a significant improvement over 2017.
      Kearns fingers the weather as 2017’s culprit. “There was a big, localized storm in late May. Winds just completely wiped out nests,” he said. Only 93 chicks survived to be counted, almost two and a half times fewer than in 2018.
     The chick count in the lower Patuxent was also good in 2016, which was different from many parts of the greater Chesapeake. Microclimates are the likely cause, Kearns explains. Even when our region gets rain, some areas stay drier than others, and he speculates that the lower Patuxent must have avoided the worst of the rain in 2016. To confirm, scientists may need to track this issue in greater detail.
     Weather is not the only challenge osprey face in raising a family. Predation by an increasing number of great horned owls is a persistent threat.
     “I figure that great horned owls take 10 to 15 percent of osprey chicks every year,” Kearns says. Raccoons can also take eggs from osprey nests, but nest guards can keep coons from reaching the young birds. But, he laments, “there’s no way to prevent great horned owls from taking osprey chicks.”
     Bald eagles also prey on osprey chicks, but Kearns has seen no evidence of eagles eating osprey, even as the eagle population continues to grow. 
     Food shortages do not seem to be a factor for Patuxent ospreys. Osprey depend on mid-sized fish, and the Patuxent has a good supply of catfish, snakeheads and goldfish — yes, goldfish. Though goldfish were originally native to Asia, they have been released and thrive worldwide, including in our local rivers.
      “Osprey will take what’s easy and abundant. Those shiny, orange fish are now making up about 20 percent of the osprey diet,” Kearns says.
      Rain redeems its sins against osprey with the blessing of goldfish. “With all the rain, the river has fresher water now than usual. Goldfish are riding the currents farther down the river, and they are easy for the birds to see,” Kearns says.
      Farther south in the Bay, food shortages may be more problematic. “Those birds depend more on menhaden,” Kearns says, “and menhaden are in trouble. Commercial fisheries are overfishing, making it hard on the osprey.”
     After 2017, biologists worried that the osprey population might be set for a significant decline — and that might yet occur. How recent climate changes play out will be critical for our osprey. 2016 and 2017 were wetter and cooler than previous years. 2018 was the wettest year on record. The rain’s well-timed halt was pure luck. 
     What will 2019 look like?
     Initial indications are not good for our osprey. We are leaving an El Niño winter, the strongest since 1998. El Niños are wet, really wet. Will this year’s rainy season end in time for osprey to raise their chicks? 
      Osprey are already arriving in our area, with St. Patrick’s Day their traditional arrival date. But in recent years, Kearns says, they’ve arrived earlier. He thinks the colder weather in 2019 delayed their return, but some are now arriving. Then we shall see how the weather treats them. 
     I’m hoping that less rain, for at least a critical period, will allow my osprey’s chicks — and the rest of the Bay’s osprey chicks — to thrive.