by Carl Strang
Today I conclude my review of early season phenology by considering arrival dates of migrant birds at Mayslake Forest Preserve. A few of these data are from late February, most are from March.
Bird arrival dates did not show quite the dramatic differences from previous years as did first flower dates or first insect appearances. Nevertheless, birds were showing up early in February and March. Relative to 2011, 16 bird species appeared a median 4.5 days early in 2012 (range 23 days earlier to 21 days later). The difference was larger in comparison to 2010: 15 bird species arrived a median 11 days earlier (range 0-31 days earlier). Finally, 16 bird species appeared a median 3 days earlier in 2012 than in 2009 (range 9 days earlier to 13 days later).
So far, the birds we are seeing are species that spent the winter in the southern U.S. They are expected to be much more responsive to weather conditions than the tropical migrants, which could not know about the early season. Therefore I expect differences in arrival dates to diminish as the migration season progresses.