Loon numbers decreasing
Many associate the call of the wild with the haunting lament of the loon, whether it be by forest lakes, or in the cottage country of Canada and the US.
We see common loons with only their heads showing above water, or watch them run across lakes to take flight. Although over 94 percent of the world’s loons breed in Canada, they are also found in the lakes and coasts of the US, Mexico, and along the Atlantic coasts of Europe.
Loons hunt by diving underwater to feed on amphibians like frogs, fish, salamanders, crayfish, and crustaceans, and nest near the shore. Once the ice melts, two olive and brown-spotted eggs are laid in May or June. Then eggs are incubated, by both the male and female, for about a month. Adults feed and protect the chicks until they fledge at about 75 days.
Male loons defend their territories with their lives to be able to keep their domains. Thus, the same females can return from migration to the same territory and breed with the same male.
Due to the placement of a loons’ legs, they are not graceful on land. The feet are at the end of their bodies, rather than in the center. To enable them to escape from predators, they nest close to the water. The word loon comes from the word lummox in Old English, or lum Scandinavian meaning lame and clumsy.
Predators like large birds (eagles), are a threat to young chicks. While skunks, raccoons, foxes, otters, crows, and ravens eat loon eggs. A baby loon is able to run, and jump into a lake for cover, within hours of birth.
Pollution problems affecting Loons
Unfortunately, the IUCN (International Union for Conservation of Nature) estimates the number of loons worldwide is decreasing.
While common loons have been good at raising their young and the chicks have survived. Traditionally, success comes because they live on clear lakes. Thus, they can see their swimming fish, and bring them back to their chicks.
Birds Studies Canada has been tracking loons for over 40 years, and has discovered that a complex web of factors is causing loons to have a successful reproduction rate of less than one percent. “Half a chick per year—it’s a really strange number,” says Kathy Jones of the non-profit organization, Birds Studies Canada.
Sadly, a 0.48 percent reproduction rate is not a promising number.
Studies near Sudbury reported in the research paper ‘The Legacy of regional industrial activity’ in Biological Conservation, have zeroed in on acid rain and concluded that although lakes can recover from acid rain, the revival of lakes after acidification is “not always straightforward. Many lakes remain too acidic to support acid-sensitive organisms despite improvements.” Declines in other chemicals like calcium that affect the thickness of birds’ eggs, also are important, and do not recover at the same rate as the sulfates studied, as well.
Another concern is that heavy metals deposited on the shore can be released back into a water source if there is a flood or high water levels. This pollution means that there are fewer fish for loons to eat, and fewer chicks survive.
In the end, according to the study, “long-term monitoring data suggest that loon productivity is declining in Ontario and across Canada and that breeding success is lower and temporal declines in productivity are steeper in more acidic lakes… It is therefore likely that the biological effects of lake acidification are continuing to negatively impact loon reproduction.”
Lakes polluted with mercury have also been found to affect loons. Ecotoxicology has “measure[d] potential negative impacts from Hg [mercury] body burdens on behavior, physiology, survival, and reproductive success… Increasing Hg body burdens reduced the number of fledged chicks per territorial pair, with highest risk loons producing 41% fewer fledged young”.
The unpredictability of climate change has also been shown to cause further stress for loons. Increasing temperatures earlier in the season mean more chicks, but not more food to feed them with. A cooler spring can result in greater numbers of a pest nicknamed the ‘Loon Black Fly’ that harass parents to the point that they stop incubating their eggs. Hotter summers have also been linked to more bird disease outbreaks like Botulism E.
Increasing areas of human habitats, boating, and fishing also have directly influenced bird numbers. Poisonous lead fishing weights are just the right size for the birds to consume, and more cottages along the shoreline mean abandonment of loon traditional nesting sites. Lead weights are also used by hunters to hold down decoys.
Sources
Canadian Lakes Loon Survey: New Report Helps Explain Mysterious Declines. (2021, August 21). Bird Studies Canada. https://www.birdscanada.org/canadian-lakes-loon-survey-new-report-helps-explain-mysterious-declines
Loon. (2023, August 27). Wikipedia. https://en.wikipedia.org/wiki/Loon
Are loons another species under threat. (2019, April 13). Radio Canada International. https://www.rcinet.ca/en/2019/04/23/are-loons-another-species-under-threat/
The world's most endangered loons. (2012, August 8). Mongabay. https://rainforests.mongabay.com/endangered/charts/birds-loons.html
Common Loon (Gavia immer). (2015, August 19). Government of Canada. https://wildlife-species.canada.ca/bird-status/oiseau-bird-eng.aspx?sY=2019&sL=e&sM=a&sB=COLO
What’s Happening to Canada’s Common Loons. (2019). Love Your Lake. https://loveyourlake.ca/whats-happening-to-canadas-common-loons/
Loon reproduction is on the decline in Canada. (2019, April 4). Cottagelife: Blue Ant Media Canada Network. https://cottagelife.com/outdoors/loon-reproduction-is-on-the-decline-in-canada/
The legacy of regional industrial activity: Is loon productivity still negatively affected by acid rain? Evers, David C.; Savoy, Lucas J.; DeSorbo, Christopher R.; Yates, David E.; Hanson, William; Taylor, Kate M.; Siegel, Lori S.; Cooley, John H.; Bank, Michael S.; Major, Andrew; Munney, Kenneth (1 February 2008). Ecotoxicology. 17 (2): 69–81. doi:10.1007/s10646-007-0168-7. ISSN 1573-3017. PMID 17909967. S2CID 17769869.
Adverse effects from environmental mercury loads on breeding common loons. Evers, D.C., Savoy, L.J., DeSorbo, C.R. et al. Ecotoxicology 17, 69–81 (2008). https://doi.org/10.1007/s10646-007-0168-7