Kejimkujik National Park and National Historic Site of Canada

Common Loon Research

Canadian Wildlife Service Loon Survey

The Canadian Wildlife Service conducted a study of common loons on 40 lakes in Kejimkujik National Park from 1988 to 1997. Dr. Joseph Kerekes determined that loons utilize lakes with a surface area of at least 20 hectares and usually breed successfully on lakes of 40 or more hectares. The results showed that the total loon population remained stable, with 39 resident pairs, while the number of chicks fledged varied considerably (average of 11 chicks per year, range from 5 to 18 chicks).

An adult loon on its grassy nest
© Parks Canada / J. Steeves

Kerekes noted that so many loons come to Kejimkujik that even marginal lakes are occupied. He commented that the relative closeness of the seacoast, where many juvenile loons live for several years until they mature, ensures a large recruitment of loons. He further noted variables, such as water level changes, predation from gulls and other species, plus possible human disturbance, that could contribute to the annual variations in the number of chicks fledged.

Common Loons and Mercury

Kejimkujik's common loons have a lower reproductive success compared with that of other North American populations. Blood samples show mercury to be the only contaminant present in unduly high levels in Kejimkujik's loons. Analyses of loon blood mercury levels in 1995 and 1996 revealed that Kejimkujik's loons have among the highest blood mercury concentrations of any loon population in North America. Since mercury is a known neurotoxin that can affect behaviour in vertebrates, it is thought that these high mercury levels are related to the loons' low reproductive success.

In 1996, the Canadian Wildlife Service-Atlantic Region and the Atlantic Cooperative Wildlife Ecology Research Network (ACWERN) of Acadia University launched a study to determine the effects of mercury on the behaviour and reproduction of loons. Joe Nocera, an Acadia University graduate student, compared the behaviour of Kejimkujik's loons to that of a population of loons demonstrating higher productivity and much lower mercury levels. Generally, as mercury levels in their blood rose, the amount of time chicks spent brooding (by back-riding) decreased and the time spent preening increased. This increase in energy expenditure was not compensated for by an expected increase in feeding rate or begging.

The results of this study showed an association between variation in time spent back-riding and changes in fledging rates. While adult behaviour did not vary significantly with mercury, results suggested an association may exist. This research confirmed the hypothesis that loons and other upper level predators could be at risk from elevated levels of bioavailable mercury.

Reference:

Nocera, J.J. and P.D. Taylor. 1998. In situ behavioural response of common loons associated with elevated mercury (Hg) exposure. Conservation Ecology 2(2):10.

Loon Population Monitoring

The current Kejimkujik common loon monitoring program, coordinated by Park staff, began in 1998. To determine loon population trends, 18 lakes were selected which represent different water conditions and on which monitoring can be continued. A number of complementary survey approaches are used to document resident pairs, breeding pairs and determine the fledging success. When a chick is fledged it is able to fly, usually when it is 11 weeks old.

Loon observations are incorporated from several sources. Regular reports are submitted by backcountry patrol staff, whose duties include surveys on many of the study lakes. Random loon observations are received from various park staff for all of the study lakes.

Trained volunteers assist park staff in special loon surveys, called Loon Watch, held twice each year. Volunteers are stationed on the study lakes and record all loon observations within a three hour observation period beginning at noon. The first Loon Watch takes place in early June with the purpose of documenting resident pairs of loons as nesting season is about to begin. The second Loon Watch, held during the third week of August, reports on broods and the distribution of non-breeding adults.

Loon Observations at Kejimkujik National Park and National Historic Site
	1984	1998	1999
Resident Pairs	24+	25 - 26	26 - 27
Breeding Pairs	15	14	15
Broods (Chicks)	14 (18)	13 (19)	11 (15)

Reference:

Hope, Peter 1999. Monitoring the common loon, Gavia immer, population on 18 lakes in Kejimkujik National Park in 1998 and 1999. Parks Canada internal report.

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