Mortality and Nest Failure
One of the best ways to discover the challenges facing loon populations is to determine those things that are killing individual loons. For more than 35 years, LPC biologists have collected dead loons and non-viable loon eggs found by LPC volunteers, the public, and LPC staff. Since 1989, necropsies and toxicological analyses on dead loons have been performed in collaboration with the Tufts University Cummings School of Veterinary Medicine.
These necropsies have revealed that the ingestion of lead fishing sinkers and jigs, and subsequent lead poisoning, is by far the largest single cause of known adult loon mortality in New Hampshire. Swallowing a single lead sinker or jig can kill a loon or other waterbird.
Click here to read about LPC’s research on the effects of lead fishing tackle on loons in New Hampshire.
Loon chicks can be killed by an older sibling, or by an intruding adult loon. The largest single source of human-caused chick mortality is from collisions with fast-moving boats and personal watercraft.
Loon nests fail for a variety of reasons. The close approach of people can cause incubating loons to flush from the nest, sometimes resulting in predation of eggs by scavenger birds and mammals. The populations of some of these predators have increased to unnaturally high levels because of the availability of human refuse. Water level changes caused by rain events, or the wake from powerboats, can swamp a loon nest and chill the eggs or wash them out of the nest. LPC has found mercury and other contaminants like PBDE and PFOS in loon eggs at concentrations that have been shown to affect the health and reproductive success of other birds (see Loons as Biomonitors).
Non-viable loon eggs collected from failed nests are weighed, measured, opened and analyzed for embryo development. Egg contents are sent to laboratories that specialize in measuring mercury and other contaminants.
The results of all necropsies and analyses are made available to federal and state wildlife agencies. Egg shells, egg contents, and tissue samples from loon adults and chicks are archived to be available for future reference and research.