April Phenology

by Carl Strang

April is the first month when I can begin to make phenological comparisons between years. I look at three sets of data from Mayslake Forest Preserve: first flowering dates, arrival dates for migrant birds, and first appearances of insects. I continue to find new species, which of course can’t be used in this analysis. One example this year was the purple dead nettle.

Not really a nettle, the plant’s square stem and lipped flowers demonstrate its place in the mint family.

This is the third year of this study, and 2011’s April flower phenology fell between 2009 and 2010. There were 8 species that bloomed earlier than in 2009, and 5 later, placing this April fairly close to 2009’s very late season. That should surprise no one. Compared to 2010, there were 3 species that flowered earlier and 12 later.

Animals showed less distinction among years. For insects, 2011 brought the earliest arrival among the three years for 3 species, 2 species were latest, and 2 species appeared between their 2009 and 2010 dates. Likewise, bird arrivals in 2011 were earliest for 10 species, latest for 4, and in the middle for 8. Birds, governed more by photoperiod, are somewhat influenced by weather but not nearly as much as flower dates, which are tied to soil temperature.



  1. June 1, 2011 at 6:03 am

    […] dates of each species between years as part of my phenology study at Mayslake Forest Preserve. As I noted a month ago, birds are less influenced by weather than are insects and plants, which form the other two legs of […]

    • natureinquiries said,

      June 2, 2011 at 8:31 pm

      Also, it would depend on whether the photographer’s image is of the first plant encountered. Usually the first flower is not particularly attractive, and for a peak photo it would make sense to wait. The hyacinth photo in the post, for instance, is the first one I saw, but clearly a better photo will come later when more of the flower buds have opened.

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