AVIS-IBIS

Birds of Indian Subcontinent

Accuracy of Egg Flotation Throughout Incubation to Determine Embryo Age and Incubation Day in Waterbird Nests (Exactitud de la Flotación de los Huevos a lo Largo de la Incubación para Determinar la Edad del Embrión y el Día de Incubación en Nidos de

Publication Type:Journal Article
Year of Publication:2010
Authors:Ackerman, JT, Eagles-Smith, CA
Journal:The Condor
Volume:112
Issue:3
Date Published:2010
ISBN Number:00105422
Keywords:Himantopus, Himantopus mexicanus, Himantopus nigricollis, Laridae, Recurvirostra, Recurvirostra americana, Recurvirostra avosetta, Recurvirostridae, Sterna, Sterna forsteri
Abstract:Abstract. Floating bird eggs to estimate their age is a widely used technique, but few studies have examined its accuracy throughout incubation. We assessed egg flotation for estimating hatch date, day of incubation, and the embryo's developmental age in eggs of the American Avocet (Recurvirostra americana), Black-necked Stilt (Himantopus mexicanus), and Forster's Tern (Sterna forsteri). Predicted hatch dates based on egg flotation during our first visit to a nest were highly correlated with actual hatch dates (r = 0.99) and accurate within 2.3 ± 1.7 (SD) days. Age estimates based on flotation were correlated with both day of incubation (r = 0.96) and the embryo's developmental age (r = 0.86) and accurate within 1.3 ± 1.6 days and 1.9 ± 1.6 days, respectively. However, the technique's accuracy varied substantially throughout incubation. Flotation overestimated the embryo's developmental age between 3 and 9 days, underestimated age between 12 and 21 days, and was most accurate between 0 and 3 days and 9 and 12 days. Age estimates based on egg flotation were generally accurate within 3 days until day 15 but later in incubation were biased progressively lower. Egg flotation was inaccurate and overestimated embryo age in abandoned nests (mean error: 7.5 ± 6.0 days). The embryo's developmental age and day of incubation were highly correlated (r = 0.94), differed by 2.1 ± 1.6 days, and resulted in similar assessments of the egg-flotation technique. Floating every egg in the clutch and refloating eggs at subsequent visits to a nest can refine age estimates.
URL:http://www.jstor.org/stable/10.1525/cond.2010.090070
Short Title:The Condor
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith