Squam Lake Loon Study

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 34-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.

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.

Could Squam’s loons simply be migrating to nearby lakes rather than expiring? LPC’s research and monitoring indicate that emigration of loons can not 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 now vacant on Squam 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, could result in adult loon mortality, but in these cases we would expect to find loon carcasses. LPC did in fact collect six adult loon carcasses on Squam between 2004 and 2008, but only two of these were collected around the period of the 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 mid-west, 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.

New Developments

In the summer of 2007, LPC biologists and volunteers 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. This breeding record was the worst observed since 1978, the year LPC successfully petitioned to add loons to the list of threatened species in New Hampshire. In 2008, only two loon chicks survived to fledge on Squam Lake.

The number of factors that could potentially affect breeding success are much larger than those that could cause mortality of adult loons. As a result of this new development, LPC expanded its study to assess these additional factors and determine, as completely as possible, the full range of impacts to Squam’s loon population.

Objectives of the Squam Lake Loon Study

The Squam Lake Loon Study includes an increased monitoring and research effort to:

1. Establish 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. Find and collect loon carcasses and test liver samples from dead loons for contaminants and pathogens;
4. Band loons to allow us to identify individual birds and collect blood and feather samples for analysis;
5. 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; and
6. Create a systems dynamics model to determine the relative contributions of a wide range of possible stressors on the mortality and reproductive failure of loons on Squam Lake.

Results To Date

Staff from Tufts University School of Veterinary Medicine and the University of New Hampshire have performed necropsies on six adult loons found dead on Squam Lake between 2004 and 2008. They found that two loons were killed by boat strikes; two were killed as a result of ingested lead fishing tackle; one was likely killed as a result of a fishing hook that had pierced its stomach wall; and one adult was killed as a result of wounds from another loon. Necropsies did not reveal excessive parasite burdens or identify other pathogens that might have contributed to the declines on Squam, but the state of decomposition of most carcasses limited our ability to detect these pathogens. Many more Squam Lake loons missing during this time period remain unaccounted for and are presumed to have died on their ocean wintering grounds. Frozen liver samples from loons collected on Squam Lake and from control lakes are being prepared for submission to a laboratory. LPC will test as many liver samples as funding allows.

A team of biologists from the Loon Preservation Committee, the Biodiversity Research Institute, and Tufts University banded 13 loons on the Squam Lakes in 2007 and 2008. Blood and feather samples were taken from each banded loon to test for contaminants and pathogens. 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 it is difficult to determine what effect the toxins might have; however, the levels found in some loons would be a cause for concern in other animals. Preliminary analyses of blood samples collected during banding have not revealed blood parasites or elevated white blood cell counts that would indicate disease. Blood serum has been frozen and will be tested for disease agents including bacteria and viruses.

LPC biologists collected 13 inviable loon eggs from failed loon nests on Squam Lake in 2007 and 2008. Initial results from four eggs collected on Squam Lake and three control lakes revealed very high levels of a number of contaminants including PFOS (a chemical used in stain guards in a wide variety of consumer goods, as well as in firefighting foam), PBDE (a widely-used flame retardant) and PCB. LPC is awaiting results of tests on other loon eggs collected from failed nests on Squam Lake in 2007 and 2008.

Plymouth State University mathematics professor Tom Boucher and students in his Special Topics course investigated the effects of a large number of variables, including air temperature, precipitation, extreme weather events, fish populations, predator populations, recreational use of lakes, and LPC’s management to mitigate these effects, on the breeding success of loons on Squam Lake. Preliminary results of these analyses have been submitted to a peer-reviewed journal.

LPC is working with Lori Siegel of Siegel Environmental Dynamics to integrate results of all of the above analyses into a systems dynamics model. This model will determine the relative contributions of a wide range of possible stressors on the mortality and reproductive failure of loons on Squam Lake.

Steps to Complete the Squam Lake Loon Study

Loons on Squam Lake experienced the greatest single-year decline ever recorded in LPC’s 34 years of state-wide monitoring.

The Squam Lake Loon Study has already provided invaluable baseline data on contaminants and other environmental stressors on loons. 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 ever undertaken. To complete the Squam Lake Loon Study, LPC will test loon eggs and loon livers collected in 2008, as well as historical samples, for 16 heavy metals, including mercury, lead, arsenic, aluminum, selenium, magnesium, and manganese; organochlorines including PCBs (polychlorinated biphenyls), DDT and its derivatives such as DDE, dieldrin, heptachloradane (insecticides); other organic pollutants such as polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), organophosphorus insecticides (OPs), polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs, or flame retardants), and other insecticides and herbicides. Blood serum and tissue samples will be tested for viruses such as those causing West Nile Virus, avian influenza, and paramyxovirus, and bacteria such as those causing botulism and salmonella. We will determine the presence and concentrations of these contaminants and pathogens in samples collected before and after the decline of loons on Squam, and from nearby lakes that have not experienced a die-off, to determine factors that might account for the decline.

A large proportion of loon eggs laid on Squam Lake are not hatching. The Squam Lake Loon Study is attempting to solve this mystery.

We anticipate that this study will help avoid future declines of loons on Squam Lake or on other lakes; bring to light what could be a much larger, more systemic problem on Squam indicated by the decline of loons; and educate ourselves and the public about loons and the factors affecting loons on Squam Lake and state-wide. The results of this study will provide basic knowledge of contaminants and pathogens in loons that is lacking at present, and baseline data which will be invaluable to assess changes in the presence and concentrations of these contaminants and pathogens in the future. Squam Lake, where LPC first began its study of loons, and arguably the home of the best-studied loons in the world, will continue to play a leading role in advancing our understanding of this magnificent bird.

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