Threats to Loons and Their Habitats
Loons are capable of adapting to a variety of conditions. However, thresholds can be crossed that will cause a nest to fail or result in the death of chicks or adult loons, particularly during the breeding season. Fortunately, many concerns related to disturbance are easily preventable. During the spring and summer months, as people recreate on their favorite lake, they should be observant of loons and remember that they share the water with a rich variety of wildlife. Observing loon behaviors and habits from a respectful distance will benefit both humans and wildlife.
Disturbance of loons by other wildlife or humans can interrupt incubation and cause a nest to fail or be abandoned. People visiting an island or canoeists/paddlers approaching a loon too closely can inadvertently cause adult loons to leave their nests, potentially for long periods of time, causing chilling of the eggs and possible failure of the nest. Loon nests and young chicks are easily swamped by the wake of a jet ski or a motorboat, resulting in chilling of the eggs or chicks, and possible abandonment by the parents.
Adult loons will vigorously “dance” on the water or call loudly to distract predators and people away from chicks or a nest. Although a disturbed loon is an amazing sight to watch as it performs this “penguin dance” and calls with tremolos or yodels, observers should recognize that they are too close, and withdraw so as to minimize interference with the raising of the young. Jet ski and motorboat operators can help significantly by staying away from the shoreline, and keeping a sharp eye out for loons (and other wildlife) while on the water, giving them a wide distance to feed and care for their chicks.
Loon eggs are susceptible to predation by scavengers such as crows, ravens, Herring Gulls and raccoons. Populations of these opportunistic predators are often higher where there are more humans because of the increased availability of human garbage providing food for them. Loon chicks often fall prey to eagles, snapping turtles, and other loons. Adult loons can also be very aggressive towards each other, sometimes causing serious or fatal injuries, such as sternal puncture wounds, to each other.
Within the Adirondack Park, some of the highest rates of development are occurring along lakeshores. The development of shoreline for seasonal, residential homes often creates an increase in recreational lake activity that coincides with critical breeding and nesting times for the common loon.
Ecological changes which have been documented as a result of shoreline development include: fewer territorial loons inhabiting developed lakes, decreased availability of potential nesting sites, reduced hatching success of loon pairs in close proximity to developed areas and increased susceptibility to scavenging predators that are attracted to human refuse. Currently, many local and regional studies are being conducted in order to assess the impacts of shoreline development and increased recreational activity on the reproductive success of loons.
Botulism & Oil Spills:
Type E Botulism (Clostridium botulinum) has been responsible for massive and devastating epidemics of piscivorous waterbird mortalities on the Great Lakes during fall migration periods. During 2000-2001, an outbreak of Type E botulism on Lake Erie produced high mortalities for many fish and waterbird species, including an estimated 3,000-4,000 Common Loons. Common Loons and other species of waterbirds contract botulism, which grows under anaerobic conditions, through the consumption of infected prey species, such as alewives and gobies.
Within hours of ingestion, weakness, inability to fly, respiratory distress and muscular paralysis of the impaired bird sets in and most individuals drown due to an inability to hold their head upright. Scientists are currently working to identify the specific biological and ecological connections between waterbird mortalities and the sources of botulism, which will aid in the development of management strategies and response plans during Botulism Type E outbreaks.
The ecological price of a single marine or inland oil spill is evident in the many immediate and long-term injurious effects to the affected ecosystem and its aquatic inhabitants. Common Loons and many other wildlife species are extremely vulnerable to the toxic effects of oil. Accidents occurring during spring and fall migration in Common Loon staging areas can be especially devastating to the regional population. Many federal, regional and local organizations deploy trained response teams and employ a variety of management strategies for responding to the impacts of an oil spill on the affected habitat and its wildlife species.
Water Level Fluctuations:
Loon nests are constructed along the shoreline, on islands or small hummocks of vegetation in the water. If the water level drops, the adults may abandon a nest, because it may become too high above the water for them to easily reach. On the other hand, if the water level rises, the nest may become flooded, resulting in chilling of the eggs and failure to survive to hatching.
Water level fluctuation also causes stirring of the sediments at the bottom of a water body. This results in increased levels of methylmercury accumulating up the aquatic food web in that water body.
Fishing line entanglement:
The incidence of injured loons related to fishing tackle in the Adirondacks and the Northeast increases dramatically during the summer fishing season, when the birds are more likely to eat a fish that has broken a line and still has line or tackle attached. If a bird ingests lead fishing tackle which is still attached to a fish, the loon will endure a slow death from lead poisoning as the tackle breaks down in its stomach. And if there is still fishing line attached when a loon swallows a fish, it will fling the line around and around its head and bill in a futile effort to get it off, thus entangling itself even more. Such a loon will likely suffer an infection as the line cuts into its flesh, may be unable to eat, and it may experience a prolonged and debilitating death.
Lead fishing tackle:
Lead is toxic to animals and humans when ingested. Loons, swans, herons and other waterbirds can die from lead poisoning after swallowing lead fishing tackle inadvertently lost by anglers. Research in the northeastern United States and Canada, where loons breed, has found that lead poisoning from ingestion of lead sinkers and jigs accounts for 10-80% of dead adult loons found by researchers. This research indicates that, in most areas, more loons die from lead poisoning than from tumors, trauma, fractures, gunshot wounds, infections, or conflict between loons.
Sport anglers attach lead weights to fishing lines to sink the hook, bait, or lure into the water. Some anglers use lead-weighted hooks, called jigs. A sinker or jig may accidentally detach from a line and fall into the water, or the hook or line may become tangled and the line may break or be cut.
Many lead sinkers and jigs are similar in appearance to the small stones and grit that birds swallow to help digest food in their gizzards. Loons and other waterbirds may also eat fish that still have a hook and sinker attached that was broken from an angler’s line.
Lead poisoning causes physical and behavioral changes in birds, including loss of balance, tremors, and impaired ability to fly. The weakened bird is more vulnerable to predators, and may have trouble feeding, nesting, and caring for young. It becomes emaciated and dies within 2-3 weeks after eating lead fishing tackle.
Mercury and Loons:
Mercury is an environmental pollutant released through a variety of industrial processes, such as coal burning, waste incineration, and metal production. Mercury emitted into the atmosphere can travel great distances on air currents before being deposited in aquatic systems. Once in waterways, this contaminant is taken up by fish, which makes it a problem for all fish-eating species, including loons and humans alike.