The Arctic_shorebird_egg_float_tool.xls was developed by Rob Rankin (updated in 2021 by Sarah Saalfeld) to estimate hatch dates, nest initiation dates, nest incubation dates, and nest age based on egg floatation equations developed by 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 & S.W. Zack. 2007. Assessing the development of shorebird eggs using the flotation method: species-specific and generalized regression models. Condor 109: 32-47.
This tool can be found in the protocol folder.
This tool provides species-specific estimates for 10 species: American Golden-Plover (AMGP), Dunlin (DUNL), Pectoral Sandpiper (PESA), Red-necked Phalarope (RNPH), Red Phalarope (REPH), Ruddy Turnstone (RUTU), Semipalmated Sandpipe (SESA), Long-billed Dowitcher (LBDO), Buff-breasted Sandpiper (BBSA), and Western Sandpiper (WESA).
To use the tool, enter correct information for date eggs were measured (‘Date Measured’; dd-mon), species (4-letter acronym), number of eggs floated (1-4), number of eggs in nest, angle of each egg, whether eggs were above or below the surface (‘y’ or ‘n’), and mm above surface (if below surface = ‘n’). When less than 4 eggs are floated, information for egg angle, below surface, and mm above surface for those eggs should be entered beginning with egg ‘1’, followed by ‘2’, etc. until all information is entered, with fields left blank for eggs with no information. All other fields within the tool should not be changed. Note that egg angles < 21 or > 89 are not allowed.
The tool will then estimate days to hatch (DTH), hatch date, initiation date, incubation date, and nest age for 3 scenarios: ‘AVERAGE’: estimates based on the average number of days to hatch across all eggs, ‘Most Conservative’: estimates based on the egg with the greatest number of days to hatch, and ‘Median’: estimates based on the median number of days to hatch across all eggs.
The tool uses the following equations for its estimations:
Days to hatch: a + blogit of proportional egg angle for sinking eggs; a + bfloat height in mm + c*egg angle in degrees for floating eggs, where a, b, and c are taken from Liebezeit et al. 2007.
Hatch date: date eggs were measured + number of days to hatch.
Initiation dates: incubation date- number of eggs in nest + 1; assuming 1 egg is laid per day.
Incubation dates: hatch date - average incubation period for a given species.
Estimated age: date eggs were measured - estimated incubation period.
With the exception of Ruddy Turnstone and Buff-breasted Sanpdiper, average incubation periods were estimated from Weiser, E.L., S.C. Brown, R.B. Lanctot, H.R. Gates, K.F. Abraham, R.L. Bentzen, J. Béty, M.L. Boldenow, R.W. Brook, T.F. Donnelly, W.B. English, S.A. Flemming, S.E. Franks, H.G. Gilchrist, M.-A. Giroux, A. Johson, L.V. Kennedy, L. Koloski, E. Kwon, J.-F. Lamarre, D.B. Lank, N. Lecomte, J.R. Liebezeit, L. Mckinnon, E. Nol, J. Perz, J. Rausch, M. Robards, S.T. Saalfeld, N.R. Senner, P.A. Smith, M. Soloviev, D. Solovyeva, D.H. Ward, P.F. Woodard & B.K. Sandercock. 2017. Life-history tradeoffs revealed by seasonal declines in reproductive traits in Arctic-breeding shorebirds. Journal of Avian Biology 49 DOI: 10.1111/jav.01531. Incubation periods for Buff-breasted Sandpiper were based on Lanctot, unpublished data, while Ruddy Turnstones were based on Birds of the World (Rodewald and Schulenberg, eds. 20200. Cornell Laboratory of Ornithology, Ithaca, NY).
For detailed information on proper egg floating techniques see the Arctic Shorebird Demographics Protocol (Brown, S. C., H. R. Gates, J. R. Liebezeit, P. A. Smith, B. L. Hill, and R. B. Lanctot. Arctic Shorebird Demographics Network breeding camp protocol, Version 5, April 2014. Unpubl. paper by U.S. Fish and Wildlife Service and Manomet Center for Conservation Sciences. Available at https://www.manomet.org/sites/default/files/publications_and_tools/ASDN_Protocol_V5_20Apr2014.pdf).
The data providers have invested considerable effort in QA/QC, but it is possible that undetected errors remain. It is strongly recommended that careful attention be paid to the contents of the metadata file associated with these data to evaluate data set limitations, restrictions, or intended use. The originators of this dataset shall not be held liable for improper or incorrect use of the data described and/or contained herein.
