Definition of "addling"

The familiar hatchery practice of agitating the eggs after they are eyed, called shocking or addling, ruptures the yolk membranes of the ever-tender sterile eggs. The result is a precipitation of the globulin and a whitening of the egg.

1980, Earl Leitritz with Robert C[onklin] Lewis, Trout and Salmon Culture (Hatchery Methods) , Oakland, Calif.: University of California Division of Agriculture and Natural Resources, page 24

Egg addling was important in several species, but it was not recorded what proportion of the unhatched eggs were fertile. Compared with the amount of egg addling in some other birds, the amount among raptors is often high. In part this addling is linked with food conditions, as mentioned, and perhaps with the nutritional state of the female.

1993, Ian Newton, “Causes of Breeding Failure in Wild Raptors: A Review”, in Patrick T[homas] Redig, John E. Cooper, J. David Remple, D. Bruce Hunter, editors, Raptor Biomedicine, Minneapolis, Minn.: University of Minnesota Press, pages 66–67

There are only two ways to remedy the mute-swan situation: Pay people to locate nests and addle their eggs (addling means shaking each egg hard to kill the embryo inside; if you smash the eggs, the birds will lay replacements, but swans will sit on addled eggs and not lay more), or authorized licensed hunters to shoot the birds. Addling is not only time consuming and expensive, but it's also dangerous because swans regard people who invade their nesting territory as just a larger kind of raccoon.

2002 July, George Reiger, “More Bad News on Big Birds”, in Field & Stream, volume CVII, number 3, New York, N.Y.: Times Mirror Magazines, page 56

[I]n 1999, we issued regulations for a special Canada goose permit to provide state wildlife agencies the ability to manage and control resident population Canada geese. These permits can authorize addling of eggs from March 11 through August 31.

2003 March 19, United States Congress, House of Representatives, Committee on Resources, Subcommittee on Fisheries Conservation, Wildlife, and Oceans, Fiscal Year 2004 Budget Requests for the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Fish and Wildlife Service: Oversight Hearing before the Subcommittee on Fisheries Conservation, Wildlife and Oceans of the Committee on Resources, U.S. House of Representatives, One Hundred Eighth Congress, First Session, March 19, 2003, volume 4, Washington, D.C.: Government Printing Office, page 47

Addling accounted for 1% of clutches laid, 1% of all nests, and 2% of all complete failures. […] In most addled clutches all the eggs remained intact, but in some, one or more eggs were broken during incubation. […] [W]hile some egg addling was due to pollutants, other addling was probably due to natural factors.

2010, Ian Newton, The Sparrowhawk, Calton, Staffordshire: T. & A. D. Poyser, page 347

Physical methods are sometimes used to reduce or eliminate fertility. Methods include physical addling and surgical sterilization. Meaning "loss of development," addling in the strictest sense is destruction of eggs by shaking. Addling has come to mean destroying eggs by any physical or chemical means – puncturing, freezing, or coating with vegetable oil.

2013, Russell F. Reidinger with James E. Miller, Wildlife Damage Management: Prevention, Problem Solving & Conflict Resolution, Baltimore, Md.: Johns Hopkins University Press, page 114