Using an 18-year dataset of arrival dates of 65 species of Maine migratory breeding birds, I take a deeper view of the data to ask questions about the shapes of the distribution. For each year, most species show a consistent right-skewed pattern of distribution, suggesting that selection is stronger against individuals that arrive too early compared to those that arrive later. Distributions are consistently leptokurtic, indicating a narrow window of optimal arrival dates. Species that arrive earlier in the spring show higher skewness and kurtosis values. Nectarivorous species showed more pronounced skewness. Wintering area did not explain patterns of skewness or kurtosis. Deviations from average temperatures and the North Atlantic Oscillation index explained little variation in skewness and kurtosis. When arrival date distributions are broken down into different medians (e.g., 5% median and 75% median), stronger correlations emerge for portions of the distribution that are adjacent, suggesting species fine-tune the progress of their migration. Interspecific correlations for birds arriving around the same time are stronger for earliest migrants (the 25% median) compared to the true median and the 75% median.
References
[1]
Pe？uelas, J.; Fillela, I.; Comas, P. Changed plant and animal life cycles from 1952 to 2000 in the Mediterranean region. Glob. Chang. Biol. 2002, 8, 531–544, doi:10.1046/j.1365-2486.2002.00489.x.
[2]
Cotton, P.A. Avian migration phenology and global climate change. Proc. Natl. Acad. Sci. USA 2003, 100, 12219–12222, doi:10.1073/pnas.1930548100.
[3]
Both, C.; Artemyev, A.V.; Blaauw, B.; Cowie, R.J.; Dekhuijzen, A.J.; Eeva, T.; Enemar, A.; Gustafsson, L.; Ivankina, E.V.; J？rviven, A.; et al. Large-scale geographical variation confirms that climate change causes birds to lay earlier. Proc. Roy. Soc. Lond. 2004, B 271, 1657–1662.
[4]
Crick, H.Q.P. The impact of climate change on birds. Ibis 2004, 146, 48–56, doi:10.1111/j.1474-919X.2004.00327.x.
[5]
Mason, C.F. Long-term trends in the arrival dates of spring migrants. Bird Study 1995, 42, 182–189, doi:10.1080/00063659509477167.
[6]
Sparks, T.H.; Carey, P.D. The responses of species to climate over two centuries: An analysis of the Marsham phenological record, 1736–1947. J. Ecol. 1995, 83, 321–329, doi:10.2307/2261570.
[7]
Bradley, N.L.; Leopold, A.C.; Ross, J.; Huffaker, W. Phenological changes reflect climate change in Wisconsin. Proc. Natl. Acad. Sci. USA 1999, 96, 9701–9704.
[8]
Sparks, T.H. Phenology and the changing pattern of bird migration in Britain. Int. J. Biometeorol. 1999, 42, 134–138, doi:10.1007/s004840050096.
[9]
Ledneva, A.; Miller-Rushing, A.J.; Primack, R.B.; Imbres, C. Climate change as reflected in a naturalist’s diary, Middleborough, Massachusetts. Wilson Bull. 2004, 116, 224–231, doi:10.1676/04-016.
[10]
Marra, P.M.; Francis, C.M.; Mulvihill, R.M.; Moore, F.R. The influence of climate on the rate and timing of bird migration. Oecologia 2005, 142, 307–315, doi:10.1007/s00442-004-1725-x.
[11]
Mills, A.M. Changes in the timing of spring and autumn migration in North American migrant passerines during a period of global warming. Ibis 2005, 147, 259–269, doi:10.1111/j.1474-919X.2005.00380.x.
[12]
T？ttrup, A.P.; Rainio, K.; Coppack, T.; Lehikoinen, E.; Rahbek, C.; Thorup, K. Local temperature fine-tunes the timing of spring migration in birds. Integr. Comp. Biol. 2010, 50, 293–304, doi:10.1093/icb/icq028.
[13]
Vitale, J.; Schlesinger, W.H. Historical analysis of the spring arrival of migratory birds to Dutchess County, New York: A 123-Year record. Northeast. Nat. 2011, 18, 335–346, doi:10.1656/045.018.0306.
[14]
Lehikoinen, E.; Sparks, T.H.; Zalakevicius, M. Arrival and departure dates. Adv. Ecol. Res. 2004, 35, 1–31, doi:10.1016/S0065-2504(04)35001-4.
[15]
Cox, G.W. Bird Migration and Global Change; Island Press: Washington, DC, USA, 2010.
[16]
M？ller, A.P.; Fiedler, W.; Berthold, P. Effects of Climate Change on Birds; Oxford University Press: Oxford, UK, 2010.
[17]
Knudsen, E.; Lindén, A.; Both, C.; Jonzén, N.; Pulido, F.; Saino, N.; Sutherland, W.J.; Bach, L.A.; Coppack, T.; Ergon, T.; et al. Challenging claims in the study of migratory birds and climate change. Biol. Rev. 2011, 86, 928–946, doi:10.1111/j.1469-185X.2011.00179.x.
[18]
Wilson, W.H., Jr.; Savage, A.; Zierzow, R.E. Arrival dates of migratory breeding birds in Maine: Results from a volunteer network. Northeast. Nat. 1997, 4, 83–92, doi:10.2307/3858406.
[19]
Wilson, W.H., Jr. Spring arrival dates of migratory breeding birds in Maine: Sensitivity to climate change. Wilson J. Ornithol. 2007, 119, 667–679.
[20]
Wilson, W.H., Jr. Variability of arrival dates of Maine migratory breeding birds: Implications for detecting climate change. Northeast. Nat. 2009, 16, 443–454, doi:10.1656/045.016.n311.
[21]
Wilson, W.H., Jr.; Kipervaser, D.; Lilley, S.A. Spring arrival dates of Maine migratory breeding birds: 1994–1997 vs. 1899–1911. Northeast. Nat. 2000, 7, 1–6.
[22]
McMahon, J.S. The biophysical regions of maine: Patterns in the landscape and vegetation. M.Sc. Thesis, University of Maine, Orono, ME, USA, 1990.
[23]
Ehrich, P.; Dobkin, D.S.; Wheye, D. The Birder’s Handbook: A Field Guide to the Natural History of North American Birds; Touchstone Press: Beaverton, OR, USA, 1988.
[24]
Sokal, R.R.; Rohlf, J.R. Biometry; W.H. Freeman Company: New York, NY, USA, 1981.
[25]
Sparks, T.H.; Barlein, F.; Bojarinov, J.G.; Hüppop, O.; Lehikoinen, E.A.; Rainio, K.; Sokolov, L.V.; Walker, D. Examining the total arrival distribution of migratory birds. Glob. Chang. Biol. 2005, 11, 22–30, doi:10.1111/j.1365-2486.2004.00887.x.
[26]
M？ller, A.P. Distribution of arrival dates in a migratory bird in relation to environmental conditions, natural selection and sexual selection. Ethol. Ecol. Evol. 2008, 20, 193–210, doi:10.1080/08927014.2008.9522522.
[27]
Butler, C.J. The disproportionate effect of global warming on the arrival dates of migratory birds in North America. Ibis 2003, 145, 484–495, doi:10.1046/j.1474-919X.2003.00193.x.
[28]
Hüppop, O.; Hüppop, K. North Atlantic Oscillation and timing of spring migration in birds. Proc. Roy. Soc. Lond. 2003, B270, 233–240, doi:10.1098/rspb.2002.2236.
[29]
V？h？talo, A.V.; Rainio, K.; Lehikoinen, A.; Lehikoinen, E. Spring arrival of birds depends on the North Atlantic Oscillation. J. Avian Biol. 2004, 35, 210–216, doi:10.1111/j.0908-8857.2004.03199.x.
[30]
Saino, N.; Szép, T.; Romano, M.; Rubolini, D.; Spina, F.; M？ller, A.P. Ecological conditions during winter predict arrival date at the breeding quarters in a trans-Saharan migratory bird. Ecol. Lett. 2004, 7, 21–25, doi:10.1046/j.1461-0248.2003.00553.x.
[31]
Gordo, O.; Brotons, L.; Ferrer, X.; Comas, P. Do changes in climate patterns in wintering areas affect the timing of the spring arrival of trans-Saharan migrant birds? Glob. Chang. Biol. 2005, 11, 12–21, doi:10.1111/j.1365-2486.2004.00875.x.
[32]
T？ttrup, A.; Thorup, K.; Rahbek, C. Patterns of change in timing of spring migration in North European songbird populations. J. Avian Biol. 2006, 37, 84–92.
[33]
Both, C. Comment on “Rapid advance of spring arrival dates in long-distance migratory bird”. Science 2007, 315, 598, doi:10.1126/science.1136148.
