A saltwater flotation technique to identify unincubated eggs

Devney, Carol A., Kondrad, Shannon L., Stebbins, Katherine R., Brittingham, Kevin D., Hoffman, David J., and Heinz, Gary H. (2009) A saltwater flotation technique to identify unincubated eggs. Journal of Fields Ornithology, 80 (1). pp. 88-93.

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Abstract

Field studies on nesting birds sometimes involve questions related to nest initiation dates, length of the incubation period, or changes in parental incubation behavior during various stages of incubation. Some of this information can be best assessed when a nest is discovered before the eggs have undergone any incubation, and this has traditionally been assessed by floating eggs in freshwater. However, because the freshwater method is not particularly accurate in identifying unincubated eggs, we developed a more reliable saltwater flotation method. The saltwater method involves diluting a saturated saltwater solution with freshwater until a salt concentration is reached where unincubated eggs sink to the bottom and incubated eggs float to the surface. For Laughing Gulls (Leucophaeus atricilla), floating eggs in freshwater failed to identify 39.0% (N= 251) of eggs that were subsequently found by candling to have undergone incubation prior to collection. By contrast, in a separate collection of gull eggs, no eggs that passed the saltwater test (N= 225) were found by a later candling to have been incubated prior to collection. For Double-crested Cormorants (Phalacrocorax auritus), floating eggs in freshwater failed to identify 15.6% (N= 250) of eggs that had undergone incubation prior to collection, whereas in a separate collection, none of the eggs that passed the saltwater test (N= 85) were found by a later candling to have been incubated prior to collection. Immersion of eggs in saltwater did not affect embryo survival. Although use of the saltwater method is likely limited to colonial species and requires calibrating a saltwater solution, it is a faster and more accurate method of identifying unincubated eggs than the traditional method of floating eggs in freshwater.

Item ID: 10491
Item Type: Article (Refereed Research - C1)
Keywords: aging eggs; egg flotation; embryonic development; incubation stage; saltwater flotation; zoology
ISSN: 1557-9263
Date Deposited: 14 Apr 2010 22:43
FoR Codes: 06 BIOLOGICAL SCIENCES > 0608 Zoology > 060899 Zoology not elsewhere classified @ 80%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060299 Ecology not elsewhere classified @ 20%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960599 Ecosystem Assessment and Management not elsewhere classified @ 60%
96 ENVIRONMENT > 9607 Environmental Policy, Legislation and Standards > 960799 Environmental Policy, Legislation and Standards not elsewhere classified @ 40%
Citation Count from Web of Science Web of Science 1
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