A Peek at ACLC’s Loon Research: What are we hoping to learn?
Now that the busy summer months are behind us, let’s look at the research ACLC does, how we do it and what it helps us understand about the loons that nest in the Adirondacks.
The Adirondack Center for Loon Conservation (ACLC) was founded as a nonprofit in 2017 to continue the research that Dr. Nina Schoch began in 1998 with Biodiversity Research Institute (BRI). This research was focused on assessing the impact of mercury pollution on breeding loon populations and aquatic ecosystems. Loons are excellent indicators of overall ecosystem health because, as top predators, they accumulate higher levels of contaminants in their body tissues than organisms lower in the food chain.
A nesting loon. Photo by Nina Schoch
ACLC researchers collect blood and feather samples from loons to be tested for mercury levels. Higher levels of mercury have been shown to impact loons neurologically and to weaken their ability to successfully nest and raise chicks. Understanding how changes in mercury levels impact common loons helps researchers understand implications for human health and the health of the ecosystem as a whole. Recently, ACLC researcher partners have also begun using the samples collected to test for the presence of PFAS, or forever chemicals, in Adirondack lakes as well.
To collect blood and feather samples, ACLC researchers plan an annual Banding Week, where staff, research partners and volunteers spend a full week dedicated to the sometimes tedious and always tiring work of capturing loons at night to take samples and band them for future identification. If researchers catch a loon that has already been banded, they can identify when it was banded and therefore the last time blood and feather samples were collected. Science is about comparisons, so being able to compare samples from the same loon over time is informative.
This past summer, a total of 18 loons were captured and sampled during Banding Week from July 31 – August 7, 2024. The loons were captured from nine territories on nine lakes throughout the park. Of the 18 captured loons, nine were adults (five male, four female), as well as one male loon who was rescued from fishing line entanglement, and nine juvenile loons. Juvenile loons are only banded if they are old enough, meaning their body size is close enough to their adult size that their legs can hold an adult-sized band. Only four of the juveniles captured in 2024 were large enough to be banded, but blood and feather samples were collected from them all. Some of the loons captured during Banding Week were already banded – notably, a male loon captured on Gray Lake this year was originally banded in 2001 on First Lake in the Fulton Chain. That means we know this male loon is at least 23 years old.
Blood samples are collected from a loon during Loon Banding Week in 2024. Photo by Denise Silfee
Dr. Nina Schoch, research biologist Griffin Archambault and wildlife technician Brendan Gruber collect samples and attach bands to a rescued loon in 2024. Photo by Denise Silfee
ACLC researchers also collect samples and band any loon that is rescued and released again throughout the year. To date in 2024, eight common loons have been rescued: four were tangled in fishing line and/or lures and four were found on the ground. Because common loons can’t walk well on land or take off from a sitting position, grounded loons are always considered loons in distress.
We share the blood and feather samples with SUNY ESF, one of our partner organizations. They analyze the samples and add the results to a decades-long dataset for evaluation of trends over time in mercury in Adirondack lakes. These results can also be used for analyses in studies looking at regional impacts, such as in this paper published in 2011.
2024 Adirondack Loon Monitoring, Sample, and Rescue Lakes
Since 1998, 550 individual loons have been captured on 97 Adirondack lakes. Of those captured, 404 have been banded (because captured juveniles are often too small to band), and 85 of the banded loons have been captured and sampled more than one time.
Banding allows us to identify individual birds, which also allows us to track them over the course of their lives and inform our understanding of common loon behavior and natural history. Observing individual banded loons takes a lot of time and many pairs of eyes. To assist with collecting observational data, ACLC hires field staff and volunteer lake monitors and interns each summer.
In 2024, ACLC had 36 staff, interns and volunteers who helped monitor 119 lakes and determine the return rate and the reproductive success of 373 banded loons. Seventy-two of those lakes were observed on a weekly basis and 48 were observed intermittently throughout the field season. Lake monitors also collected 47 non-viable eggs from 31 lakes. Eggs and eggshell fragments can be sampled for the presence of mercury and tested for other potential reasons they were not viable.
2024 intern Britta Gaetjens collects eggshell fragments from a nest. Photo by Denise Silfee
Field staff and volunteer lake monitors record the presence or absence of loons in a given territory, the status of banded loons in a given territory, and reproductive efforts of the loons in the given territory – did they successfully build a nest and lay eggs, did those eggs hatch, did the chicks survive to fledge, etc. They also record instances of eagle-loon interactions and instances of predation to nests, as well as nest measurements, such as how far the nest is from the water’s edge. All of these variables allow ACLC researchers to look for answers to a wide range of questions, such as evaluating the impact of climate change on loon nest and chick survival. To learn more about what it’s like to monitor loons on a lake in the Adirondacks, read about the experiences of longtime field staff member Nicole Crist.
The Annual Loon Census in New York is another way ACLC gathers information about the overall population of common loons in the state. With the help of hundreds of volunteers who go out to assigned lakes on an appointed day and time to count how many loons they see, researchers get a “snapshot” that allows them to estimate the total number of loons in New York. This year, 400 volunteers looked for loons on 375 lakes. The census results are still being processed, but will be updated on the census page of our website and in an edit to this article when they are ready.
One of the last ways ACLC contributes to a broader understanding of loon biology and ecosystem health is to collect loon carcasses to be delivered to the New York State Department of Environmental Conservation’s Wildlife Pathology Laboratory for necropsy. By performing a necropsy on deceased loons, researchers can get a better picture of how threats like lead poisoning from lead fishing tackle and diseases like avian malaria are impacting the loons that call the Adirondacks their summer home. This year, 21 carcasses (16 adults, five juveniles) were sent to the lab. Results are pending and will be reported once they are all in.
Common loons swimming together. Photo by Denise Silfee
The work of science often feels slow – it involves collecting sometimes tiny-seeming details to answer very specific questions about how our world works. That means that sometimes it can be hard to keep the end-goal in focus, but each data point collected contributes to a more complete picture of the Adirondack lake ecosystem and the health of the loons who nest here.
We appreciate the dedication of our seasonal field staff, volunteers and interns, as well as our research and community partners, for all of the ways they support our work. Whether they’re dragging a kayak to the lake shore on a day threatening rain to check on a nesting pair of loons in July, or analyzing samples in a lab, or helping us fund new educational exhibits to improve the ways we communicate with our Loon Center visitors, every little bit contributes to a more complete picture of loons and the Adirondack lakes we love.
To learn more, check out our publications page on our website. You can view scientific publications as well as summary reports of what we’ve learned so far.
Words & Images by Denise Silfee, ACLC Education & Communications Director