Using data from Liebezeit et al. (2007), the graphs and calculation panels presented below allow you to estimate the incubation stage of shorebird eggs. You may either use the graphs (e.g. prints for use in the field) or you may use the panels, in both cases after having digitised the average incubation period (days from 17 to 28) for the species in question. When using the graphs for floating eggs, we recommend that you put most emphasis on float height rather then float angle. The best accuracy can be obtained by using the functions at the bottom of the page. Descriptions of errors associated with these functions based on regression can be found in the following paper:

Liebezeit, J.R., P.A. Smith, R.B. Lanctot, H. Schekkerman, I. Tulp, S.J. Kendall, D.M. Tracy, R.J. Rodrigues, H. Meltofte, J.A. Robinson, C. Gratto-Trevor, B.J. McCaffery, J. Morse and S.W. Zack 2007: Assessing the development of shorebird eggs using the flotation method: species-specific and generalized regression models. – Condor 109: 32-47.