May Phenology: Flowers and Insects

by Carl Strang

Probably the best phenological comparisons between years involve plants. That is because plants respond to soil conditions, which average the weather for the year to date. Also, there are many species of plants, increasing the number of comparisons that can be made and reducing the chance for error. I focus mainly on first flower dates. This year I was able to compare 41 species to 2010, and 44 species to 2009. The continued cool spring has made this the latest of the 3 years for first flower dates in May. The median values for 2011 were a whopping 14 days later than in 2010, and 4 days later than 2009, which also was a remarkably late year.

The wild hyacinth did not closely match the overall pattern, blooming 7 days later than in 2010 and 6 days earlier than in 2009.

The final set of phenology data I record are first observations of insect species. Here the results are shakier, in part because the number of species is small for May, at around 10, and in part because of the possibility of missing representatives of the year’s first generation of a species.

I saw the first tiger swallowtail at Mayslake Forest Preserve 16 days earlier than in 2010, 8 days earlier than in 2009.

The median dates for 2011 were 7 days earlier than in 2010, and 12 days earlier than in 2009. However, if I leave out species with more than one generation in which I obviously missed the first in the earlier years, medians shift to 9 days later than in 2010, 5 days later than in 2009.

The four-spotted skimmer shows how wildly erratic the insect data can be. My first observation for 2011 was 9 days later than in 2010, but 61 days earlier than in 2009.

Adjusting the data in that way is sensible, and produces a result consistent with what we see in the plants.

1 Comment

  1. jomegat said,

    June 2, 2011 at 11:58 am

    I used to log dates of when I saw plants in bloom, but haven’t really done any of that this year. Bad me. Then the idea occurred to me that a researcher could mine photography blogs for phenological data. I think it would be better to extract dates from EXIM data rather than base it on the photographer’s recollection. EXIM data is probably more reliable than human memory. Now that many cameras come equipped with GPS receivers, a researcher could mine that data as well. I bet Flickr is full of unmined phenology.

    Of course… it’s not quite a random sample.

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