Osprey Nation 2023: A decade of careful monitoring shows a large and widespread Osprey population in Connecticut
November 20, 2023—Ospreys are thriving in Connecticut, and interest in these beautiful, fish-eating raptors is thriving as well.
This was the 10th year of Connecticut Audubon’s Osprey Nation monitoring program. The volunteer Osprey nest stewards found and mapped 688 active nests. By the end of the season, 881 baby Ospreys had fledged — the most ever recorded by the project.
This year’s work was overseen by our Osprey Nation coordinator, Nick Ferrauolo, who wrote the 2023 Osprey Nation report, just posted to our website. It includes a summary of the year, a brief history of the decline and rise of the Osprey population, a discussion of this year’s results, and a synopsis of a new effort to collect data on the rate at which Ospreys return to their nests with fish they have caught.
Read the 2023 Osprey Nation report here.
Osprey Nation relies on volunteers who sign up in spring to observe nests, and then visit the nests a few times a month into August, to watch for signs that the birds are nesting and raising young. They submit information about what they’ve seen, and we put it on the Osprey Nation map.
This season, 411 people volunteered to be stewards, and many others helped unofficially. Most of the stewards were experienced veterans of the program—263, or 64 percent participated in Osprey Nation in the past. That means there were 148 first-time volunteers, an indication that the program continues to draw new participants.
5 Takeaways from the Osprey Nation report
|The use of DDT after World War II prevented Osprey eggs from hatching. By 1970 there were only eight nests in Connecticut. This year there were 688.|
|Most Ospreys nest near Long Island Sound and the state’s major rivers. But nests were found for the first time in Chaplin, Griswold, North Windham, and New Preston.|
|Observers found 111 nests that had not been mapped previously. This probably indicates the population is growing and expanding.|
|411 people volunteered for Osprey Nation. 148 of those were new to the program.|
|The number of fledglings per nest declined for the second year.|
Collectively, they found more Ospreys and nests than ever before. They also found 111 nests that were new or had not been mapped before, some in towns for which there were no records of Ospreys ever having nested.
The highest concentration of Ospreys continues to be near Long Island Sound and along the state’s largest rivers—the Connecticut and the Housatonic—where it’s easiest for the birds to find fish to eat.
But the discovery of nests in new areas probably indicates the population is growing and expanding, and so birds are looking for new places to nest.
There were Osprey nests this year in Chaplin, Griswold, and North Windham in the eastern part of the state, and New Preston in the west—all of them new to our database. Despite the record number of nests, the number of fledglings per nest declined for the second year. There are several possible explanations.
One might be that there was a burst of mid-season interest in the project. Many stewards signed up in early July, responding to our call for more nest coverage statewide. However, some stewards were unable to make subsequent observations, leaving the final designation of those nests as active with no confirmed fledglings.
We assume that young birds fledged from at least some of those nests, and the influx of mid-season monitoring significantly contributed to the understanding of how many active nests are in the state. But going forward, we’ll be working harder to encourage people to sign up early in the season and to continue monitoring through the summer.
Another potential reason for the observed decline in productivity might be that Osprey Nation stewards have become so numerous and widespread that they have found almost all the nests in the state (even though there’s no way of knowing exactly what that number will be).
With increased monitoring coverage, the project is discovering more nests in places where they were not expected. It’s possible that these nests are less productive because Ospreys were forced to find nests in lower quality habitat than the nests identified in the early years of the project, potentially indicating that the population is nearing carrying capacity.
The effort to determine the rate at which Ospreys return to the nest with fish is called a prey delivery rate analysis. By comparing differences in how often adult Ospreys deliver fish to the nest, it might be possible in the future to recognize differences in habitat quality; it might also indicate that the fish population is declining because of underlying and unrecognized environmental problems. The 2023 Osprey Nation report includes a full discussion of the prey delivery rate analysis.
Fledglings per nest