This is indirectly related to birds, in that the insects the birds are feeding upon (such as leafrollers, or Tortricidae moth larvae, which may have irruptive cycles), may predominantly be found on the leaves of certain species of hawthorns. If one could identify the species of hawthorns in your back yard, neighborhood, town park, or birding patch, and if we had a better understanding of the insect ecology or lifecycle, or other external factors such as weather, we may better be able to predict which hawthorns may be a desirable foraging species for neotropical migratory birds on any given year.
On the topic of identifying different species of hawthorns, I recently stumbled upon an excellent reference guide to identifying hawthorn tree species. While visiting the Collectors’ Corner at the Friends of the Library Book Sale in Ithaca, I found and purchased a signed copy of Haws: A guide to Hawthorns of the Southeastern United States. This book is an amazingly detailed 518 page one-of-a-kind field guide with various dichotomous keys, tons of color photographs, full of species descriptions and the natural history of hawthorns. This book does wonders toward dispelling the myth and previous notion that hawthorns are only a complex mass of cross-bred and unidentifiable hybrids. If interested, I found the author’s main site where you can obtain a hard copy: http://www.floramontivaga.com/about-us.html E-books are available from various sites, including Amazon (Kindle): https://www.amazon.com/Guide-Hawthorns-Southeastern-United-States-ebook/dp/B00OPNWFEM Hopefully this guide may be useful to those who wish to tease apart the hawthorn ID mystery, as it relates to neotropical migratory bird foraging strategies. Good birding! Sincerely, Chris T-H -- Chris Tessaglia-Hymes PO Box 488 8 Etna Lane Etna, NY 13062 607-351-5740 -- Cayugabirds-L List Info: http://www.NortheastBirding.com/CayugabirdsWELCOME http://www.NortheastBirding.com/CayugabirdsRULES http://www.NortheastBirding.com/CayugabirdsSubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/cayugabirds-l@cornell.edu/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/Cayugabirds 3) http://birdingonthe.net/mailinglists/CAYU.html Please submit your observations to eBird: http://ebird.org/content/ebird/ --
