Squam Lake Loon Initiative
Between the fall of 2004 and the spring of 2005, Squam Lake lost seven of its loon pairs. The decline from 16 to 9 pairs represented 44% of Squam’s loon population, a drop unprecedented on Squam or any other large lake in LPC’s 35-year history of monitoring loons throughout New Hampshire. It also brought Squam’s loon population to its lowest level since LPC began to survey Squam Lake in 1975.
Click here to watch the Squam Lake Loon Initiative Video.
Testable Hypotheses About the Decline of Squam Lake Loons
Based on the timing and the localized nature of the event (surrounding lakes did not experience declines), LPC hypothesized that a contaminant that was bound to fat cells could have played a role in this decline. Over the summer months loons generally enjoy a neutral or positive energy balance; the food they take in equals or exceeds their energy requirements, resulting in the creation of fat reserves. Many contaminants in our environment are lipophyllic (attracted to fat cells) and bind to these cells, where they are sequestered and not circulating in the blood stream.
In the fall when loons molt, they grow an almost entirely new set of feathers. Since feathers are made of protein, this is an energetically costly process, and loons draw on their stored energy reserves and metabolize fat cells during molt. As fat cells are mobilized, contaminants bound to these cells can be released into the blood stream, resulting in a flush of contaminants through a loon’s system. The stress of feather molt is followed by the stresses of the fall migration to wintering grounds, and physiological changes associated with a change from a freshwater to a saltwater environment. We hypothesize that if loons arrive at their ocean wintering grounds in a compromised state, they could be expiring on the ocean. Another hypothesis is that the effects of pathogens (disease-producing agents like parasites, bacteria, viruses, and fungi) in the Squam Lake ecosystem could become acute during these fall stressors and contribute to winter mortality.
Often-asked Questions About the Decline of Squam’s Loons
Could these contaminants and/or pathogens be coming from the ocean, rather than from Squam?
LPC’s data indicates that ocean contaminants and pathogens, while present, are unlikely to be the driving force behind the decline of loons on Squam. Data from banding done by LPC and the Biodiversity Research Institute in Gorham, Maine, indicates that Squam’s loons do not migrate or overwinter as a group. Loons breeding on Squam probably overwinter over a large stretch of the Atlantic, from Maine to Rhode Island. Therefore, any contaminants or pathogens picked up on the ocean would affect loons on many lakes and not be specifically focused on Squam as these declines seem to be. Research also indicates that the materials in eggs primarily come from recent (within three week) dietary sources, an additional fact pointing to Squam as the source of contaminants in loon eggs. Stable isotope testing conducted by LPC on these eggs indicated that, while there may be some mix of freshwater and ocean sources supplying nutrients to the egg, the majority of the material deposited in the egg comes from freshwater sources.
Could Squam’s loons simply be migrating to nearby lakes rather than expiring?
LPC’s research and monitoring indicate that emigration of loons cannot explain the drop in Squam’s loon population. We know from tracking the movements of banded loons that few loons disperse farther than 10 miles after they have lost a territory. LPC has not recorded an increase in the loon population of neighboring lakes, and banded loons that have disappeared from Squam have not been sighted on other lakes. These findings suggest that the territories vacated on Squam during the decline are a result of mortality, rather than emigration of loons.
Could recreational use of Squam Lake account for the decline?
Recreational use on Squam is more likely to affect loon breeding success than survival of adult loons. The close and/or repeated approach of boats could cause loons to leave eggs or chicks unattended and result in fewer fledged loon chicks, but boats are less likely to kill adult loons outright. Collisions with fast-moving boats or ingesting lead fishing tackle do result in adult loon mortality; but, in these cases, we would expect to find loon carcasses. LPC did in fact collect nine adult loon carcasses on Squam between 2004 and 2011, but only two of these were collected around the period of the abrupt decline.
Could the Squam eagles be contributing to the decline?
Like recreational use of Squam, eagles are more likely to contribute to reduced productivity of loons than to mortality of adult loons. There have been a few cases of eagles predating adult loons in the Midwest, but these loons are only half to two-thirds the size of our large New England loons. Eagles established themselves on Squam in 2002 and first bred successfully in 2003, and Squam loons fledged 26 chicks over those two years. It is possible that Squam’s eagles might have developed a taste for loon chicks over the past several years, but LPC has not heard of any eye-witness accounts of eagles predating loon eggs, chicks or adults on Squam.
Could density dependence (i.e., too many loons) on Squam have contributed to the decline?
Data collected by LPC since 1975 does not indicate that density dependence is a factor on Squam Lake. Although loon chicks have been killed on Squam by intruding loons, there is no clear relationship between the number of loons recorded on the lake and the rate of chick survival on Squam. If density dependence was impacting adult loons, we would expect to find carcasses of adults killed by other loons. Since 2004, only one adult loon has been collected on Squam that was killed by another loon.
In 2007, LPC recorded three new pairs of loons on the lake after two years of record low loon populations. However, this welcome news was tempered by the near-complete reproductive failure of the loon population. Only three chicks were hatched on Squam Lake, and only one survived to late August and was presumed to have fledged. Loons on Squam have not experienced a reproductive failure of this magnitude since 1978, the year LPC petitioned, successfully, to have loons added to the Threatened Species list in New Hampshire. Since 2008, Squam has regained two more pairs of loons, but reproductive success of loon pairs has remained far below pre-2005 levels (Figure 1).
Figure 1: Loon populations and breeding success on Squam Lake before, during and after the 2005-2007 period.
Increased human use of Squam Lake, and the establishment of eagles on the lake, might contribute to lowered breeding success of Squam’s loons. However, there is no known mechanism to link either of these factors with the large-scale die-off of adult loons between breeding seasons. Since loons are recognized as indicators of the health of aquatic ecosystems, the decline of Squam’s loons could mark a serious environmental problem on the lake. Squam residents and visitors use the lake for recreation and for fishing; therefore, the decline indicates a potential human health concern on Squam as well. Residents have reported changes in fish populations on Squam, including a decline in yellow perch and an increase in smallmouth bass. Food web changes such as these can significantly alter the biomagnification of contaminants in aquatic food webs and introduce new pathogens into lake ecosystems.
The Squam Lake Loon Initiative
The Squam Lake Loon Initiative begun in 2007 includes an increased monitoring, research, management and outreach effort to: 1. Determine the overall survival and reproductive success of Squam’s remaining loon population; 2. Assess causes of nest failure and collect inviable eggs from failed nests for analysis of a wide range of contaminants and pathogens; 3. Rescue sick or injured loons to increase loon survival whenever possible; 4. Find and collect loon carcasses, determine causes of death, and test liver samples from dead loons for contaminants and pathogens; 5. Band loons to allow us to identify and track individual birds and collect blood and feather samples for analysis; 6. Determine survival and breeding success of previously banded and sampled loons, and relate survival and breeding success of individuals to their levels of contaminants and pathogens; 7. Incorporate results into a systems dynamics or other explanatory model to determine the relative contributions of a wide range of possible stressors on the mortality and reproductive failure of loons on Squam Lake; and 8. Restore and maintain a healthy and stable population of loons on Squam Lake as a component of a healthy statewide population of loons.
Intensive monitoring efforts since 2007 confirmed continued low numbers of loon chicks on Squam Lake. The number of factors that could potentially affect breeding success of loons is much larger than those that could cause mortality of adults. Therefore, LPC expanded its original study of loon mortality to assess these additional factors and determine, as completely as possible, the full range of impacts to Squam Lake’s loon population. LPC has expanded its regular field season on the Squam Lakes from 12 to 14 weeks to look for early- and late-season loon mortality and measure the survival and breeding success of loons banded in previous years.
Contaminants in Squam Lake Loon Eggs
LPC staff collected 41 inviable eggs from failed loon nests on Squam Lake from 2001 to 2011. In conjunction with the Biodiversity Research Institute (BRI), LPC has tested a large number of these eggs for mercury concentrations. LPC has also tested 17 of these eggs and four eggs from control lakes to date for a wide range of heavy metals and other contaminants. Eggs collected from Squam between 2005 and 2007 revealed high levels of a number of contaminants, including PBDE (flame retardants), PFOS (stain guards), PCB (industrial insulating/cooling agents), and chlordane (a pesticide). Statistical analyses of contaminants showed that levels of contaminants in eggs collected during the decline and subsequent reproductive failure of loons (2005-2007) were significantly higher than levels in Squam Lake loon eggs collected after this period. Eggs collected in the years before this period suggest a gradual increase in contaminant levels, but further research is necessary. Levels of contaminants from Squam during 2005-2007 were also significantly higher than levels found in eggs collected from other lakes in New Hampshire, as well as eggs collected from Maine and New York lakes by BRI (Figures 2,3,4).
Figure 2: Levels of PCB in loon eggs collected on Squam Lake during the decline, outside of the decline, and from reference lakes.
Figure 3: Levels of Chlordane in loon eggs collected on Squam Lake during the decline, outside of the decline, and from reference lakes.
Figure 4: Levels of BDE-99 in loon eggs collected on Squam Lake during the decline, outside of the decline, and from reference lakes.
Other contaminants including DDT, PFOS and Strontium were also present in generally higher levels in Squam loon eggs collected during the 2005-2007 period than in eggs collected before or after this period, or in eggs collected on reference lakes (Figures 5,6,7). However, differences were not statistically significant or only marginally significant. Larger sample sizes of eggs might have revealed statistically significant differences in levels of these contaminants as well.
Figure 5: Levels of DDT in loon eggs collected on Squam Lake during the decline, outside of the decline, and from reference lakes.
Figure 6: Levels of PFOS in loon eggs collected on Squam Lake during the decline, outside of the decline, and from reference lakes.
Figure 7: Levels of Strontium in loon eggs collected on Squam Lake during the decline, outside of the decline, and from reference lakes.
LPC tested three liver samples from loons collected on Squam Lake and three samples from loons on other lakes for the same set of contaminants tested in eggs. Levels of some contaminants were high in livers from both Squam Lake loons and other loons; however, results were highly variable, due in part to differences in sex, age, body condition and time of year collected. We found that eggs provided a more useful sample because of the relative uniformity and comparability of samples.
Our knowledge of the effects on loons of these contaminants, and especially combinations of contaminants, is very limited. However, some of these contaminants were present in loon eggs collected from 2005 to 2007 at levels that have been shown to affect the physiology, health and/or reproductive success of other species, and some contaminants were present in Squam Lake eggs at levels that were many times greater than in eggs from other lakes. Eggs collected on Squam Lake after 2007 have showed lower levels of contaminants than eggs collected between 2005 and 2007.
Causes of Mortality of Squam Lakes Loons
Staff from Tufts University School of Veterinary Medicine and the University of New Hampshire Veterinary Diagnostic Laboratory have performed necropsies on nine adult loons from Squam Lake that were found dead between 2004 and 2011 and the banded Moon Island female that died after an attempted rehabilitation in 2008. Five loons were killed as a result of ingested lead fishing tackle; two loons were killed by boat strikes; one was killed as a result of wounds from another loon; and one (the Moon Island female banded in 2006) died as a result of a gunshot wound (Figure 8). One of the lead-poisoned loons (the Moon Island female banded in 2011) was collected on the coast in Massachusetts but had ingested a freshwater jig. It is unknown whether she ingested this jig on Squam or elsewhere in migration. Necropsies on these loons did not reveal excessive parasite burdens or identify other pathogens that might have contributed to the declines on Squam. Many more Squam Lake loons missing during this time period remain unaccounted for and are presumed to have died on their ocean wintering grounds.Most of the dead loon chicks collected by LPC on Squam in recent years were killed by intruding loons. LPC’s monitoring of the health of Squam’s loons (see below) has revealed the impact of parental impairment on attacks by intruding loons and subsequent loon chick mortality. In 2010, an intruding loon killed the chick at Great Island while its parent was suffering from lead poisoning after ingesting a lead-headed fishing jig. In the same year, two other chicks at the Yard Islands were killed after one of the adults tested positive for high bile acids, indicating liver dysfunction. We will continue to collect any dead loons found on Squam and collaborate with Tufts University and the University of New Hampshire to necropsy loons and analyze and/or archive tissues.
Figure 8: Causes of death of necropsied adult loons collected from Squam Lake, 2004-2011. Adults missing in 2005 and presumed dead on wintering grounds are not included in these totals.
Banding and Blood and Feather Tests
A team of biologists from the Loon Preservation Committee, the Biodiversity Research Institute, and Tufts University captured 38 loons on the Squam Lakes and banded 18 previously un-banded loons from 2007 to 2011. Blood and feather samples were taken from each captured loon to test for mercury, and eight blood samples taken in 2008 (six from Squam and two from Little Squam) were tested for a number of pathogens. Analyses of these blood samples did not reveal blood parasites or elevated white blood cell counts that would indicate disease. Blood serum was tested for disease agents including bacteria and viruses. The Little Squam female loon tested positive for aspergillosus, a fungal pathogen that affects birds with compromised immune systems. This bird was later entangled in monofilament fishing line and eluded our attempts to capture her and remove the line. She has not been resighted on Little Squam Lake or any other New Hampshire lake to date and is presumed to be deceased. The Moultonborough Bay female tested positive for exposure to avian influenza. She survived to return to Moultonborough Bay in 2009-2010 but did not return in 2011-2012 and has not been resighted elsewhere.
Similar health tests were performed on Squam loons in 2010. Notably, heretophil/lymphocyte (H/L) ratios were dramatically higher in 2010, indicating a higher level of chronic stress in loons sampled in 2010 than 2008. Hot weather during the 2010 breeding season is one possible explanation for this shift, since H/L ratios have been shown to indicate heat stress (among other stressors) in domestic poultry. Besides the loon from Yard Islands with high bile acids, blood tests identified another individual with potential health problems. The Great Island female showed signs of blood loss anemia, possibly from a conspecific injury. She returned to nest in 2011 but did not return in 2012. Also in 2010, the male from Rattlesnake Cove was entangled in fishing line late in the summer, eluded our attempts to capture him and remove the fishing line, and has not been resighted. He is presumed deceased.
Feathers taken from loons on Squam Lake and other lakes in New England revealed the presence of cyanobacteria toxins. This is the first time loons have been tested for cyanotoxins and we do not know what effect the measured levels of these toxins might have. Levels found in some loons would be a cause for concern in other animals; however, levels found in loons on Squam were lower than those found in loons on some other lakes.Over time, the existence of a significant number of banded loons on Squam Lake will allow us to track the survival, breeding success and wintering locations of Squam loons and the influence of a wide range of environmental stressors on these parameters. Banding can also reveal other poorly-understood life history aspects of loons; for example, a chick hatched on Moon Island in 2001 was resighted in 2007 as one of a mated pair of loons on Pleasant Lake near New London, a remarkable distance from its natal lake. She has returned to that lake every year since 2007.
In conjunction with the New England Field Office of the United States Fish and Wildlife Service and the New Hampshire Department of Fish and Game, LPC staff captured a number of yellow perch and smallmouth bass from Squam Lake and from a control lake to determine concentrations of a subset of contaminants in fish species preyed on by loons. These samples are being analyzed to help determine possible sources of contaminants being observed in loons on Squam Lake. Future sampling to identify possible sources of contaminants may include invertebrates, water, and/or sediment samples.
The Squam Lake Ecosystem Model
LPC is working to integrate results of all of the above analyses into a model to better understand recent changes in Squam’s loon population (see Figure 9). This model seeks to gain insight into whether any given stressor is enough to drive the population decline or, as might be expected in such a complex system, is enough to compromise the integrity of loons such that, in concert with other stressors, it threatens the population. In elucidating these stressors the model will help LPC and others make more informed decisions to protect Squam’s loons and the ecological integrity of Squam Lake.
Figure 9: Graphical representation of a small part of the Squam Lake Loon Systems Dynamics Computer Model, prepared by Lori Siegel of Siegel Environmental Dynamics.
Data gaps, including a lack of quantifiable data on populations of prey fish and populations of many egg and chick predators, have resulted in much uncertainty in the estimates of many relationships within the model. However, simulations suggest several possible causes of the recent declines in adult loons and reproductive success of loons on Squam. These include contaminant levels in eggs; increasing temperature trends that could potentially result in changes in human use of lakes, incubation, and increased egg predation and cyanobacteria concentrations; low- and high-powered boating; and fish integrity. The functional relationships driving the model are still preliminary, and definitive statements regarding causes of the loon decline and how to better manage loons and Squam Lake to prevent future declines are not yet possible. However, new data can be incorporated into the model as they become available, and current information in the model reveals interrelationships of factors and identifies probable contributors to the decline.
The Squam Lake Loon Initiative has already provided critical baseline data on contaminants and other environmental stressors on loons which will be invaluable to assess changes in, and effects of, contaminants and pathogens in the future. The collaboration of researchers formed as a result of the decline of loons on Squam Lake is unprecedented, and the testing being done on loon samples is the most comprehensive undertaken anywhere to date. The achievement of the Squam Lake Loon Initiative objectives will result in an accurate record of loon populations and productivity on Squam Lake in future years, including causes of nest failures; the quick response to sick or injured loons to increase chances of survival of these loons; an increased number of banded and sampled loons on Squam to increase our knowledge of the survival and breeding success of known individuals, and the relationship of survival and breeding success with contaminant burdens; a refined model to elucidate the effects of multiple co-occurring stressors on the survival and breeding success of loons; and management and outreach sufficient to recover and maintain the Squam Lake loon population. We anticipate that this initiative will help avoid future declines of loons on Squam and on other lakes; bring to light what could be a much larger, more systemic problem on Squam indicated by the decline of loons; inform other LPC initiatives such as the New Hampshire Loon Recovery Plan; and help LPC and others make more informed decisions to protect Squam’s loons, other wildlife, and the ecological integrity of Squam Lake, as well as lakes throughout New Hampshire.
Squam Lake will continue to play a leading role in advancing our understanding of loons and their challenges in New Hampshire. Determining the causes of the declines of loons on Squam Lake is the first step in reversing these declines and protecting Squam’s loons. Funds raised to support LPC’s continuing work on Squam will help LPC to continue to extend its field seasons on Squam; test additional samples to increase our understanding of the role of contaminants in loon mortality and reproductive failure, and track changes in contaminants levels over time; educate lake users to encourage a culture of respect and appreciation for loons; and manage Squam’s loons to recover a healthy population of loons on the lake. Thank you for your support of our work!
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