Variegated Fritillary

Variegated Fritillary

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Butterfly Research in Boulder County 2004 - 2007


In 2007, surveys recording the numbers of butterfly species and individuals were performed on a total of 39 survey days in 15 different locations within Boulder County. These surveys were conducted in a variety of habitats, ranging from prairie grasslands to upper montane forests. In addition to extending previous multi-year studies in areas such as Heil Valley, Caribou Ranch, and Cal=Wood Education Center, this year's research included butterfly inventories in an area not previously surveyed by our team, the productive Southeast Buffer prairies managed by Boulder County Parks and Open Space (BCPOS). Specifically, this year's research was conducted to extend the county butterfly database generated in previous years, determining butterfly species’ locations and population numbers, flight periods, and host or food plant interactions. Locating rare or uncommon butterfly species for this county was an additional objective of our group.

A notable phenomenon this year was the appearance of many migrant species that took advantage of the county's wealth of rich nectar sources resulting from heavy rainfall in April and plentiful groundwater. Three migrant butterfly species not previously reported by our team were observed in 2007, including: Southern Dogface, a county record discovered in 2005 by this research team, was again located in 2007. Two rare skippers – Arogos (Atrytone arogos) and Ottoe (Hesperia ottoe) – remain elusive, providing a compelling reason to continue the search in 2008. 

Some of the significant trends observed from this year’s surveys include an increase in the number of Variegated (Euptoieta claudia) and Aphrodite (Speyeria aphrodite) Fritillaries, as well as Black Swallowtails (Papilio polyxenes), in a variety of locations and habitats; a decrease in the number of Hoary Commas (Polygonia gracilis), Field Crescents (Phyciodes pulchella), and Western Pine Elfins (Callophrys eryphon) in appropriate habitats; and a record high number of butterfly species and individuals reported at the annual Cal-Wood 4th of July butterfly count, along with a record number of human participants in this public educational event.


In 2007, the Boulder County Nature Association (BCNA) generously funded our annual butterfly research project. This grant helped to extend the butterfly inventory an additional year, allowing us to continue to build a valuable long-term database. We are very grateful for BCNA’s support. Our research team has conducted butterfly surveys on Boulder County Parks and Open Space (BCPOS) lands for six consecutive years (from 2002-07). BCPOS, through their Small Grant Program, provided funding to support this research from 2004-06. Special permits were granted that allowed our researchers the privilege of access into BCPOS lands. We gratefully acknowledge the support and assistance of the BCPOS managers and staff. (There are more acknowledgments in the full report.)