A Comprehensive Annotated List of the Butterflies
Sheyenne National Grassland Butterfly Survey
Study Area and Methods of Sampling
The site of this study was lands within the general extent of the Sheyenne National Grassland in southeastern North Dakota. Two sampling procedures were employed. These are referred to respectively as "Pollard transect" (or simply "transect") and "checklist" methods. In order to ensure adequate replication, only one Pollard transect was employed. It was an 800-meter rectangular transect at the southwestern end of the North Country Trail segment in the N 1/2 of Section 27, T134N R54W, beginning 5 meters north of the sign marking the trail's beginning. The rectangle, 300 x 100 meters, begins with a 300-meter leg on a bearing of 70 (magnetic), followed by a 100-meter leg on a bearing of 160 , another 300-meter leg on a bearing of 250 , and ending with another 100-meter leg on a bearing of 340 . This transect was marked at each 50 meters by an inverted metal electric fence post, the triangular anchor of which has been painted blaze orange, marked for distance and flagged with plastic ribbon. Owing to a lack of woody material for attachment of flagging and the omnipresence of cattle, 10-meter segments were not marked. The entire transect represented true native prairie, although it was lacking in the usual diversity of forbs one expects from prairies in this region of the state. This is no doubt due in part to invasion of Poa, which was represented intermittently throughout the transect. There were some patches of willow and drier, shorter prairie intermittently dispersed along the route. This site was selected to include native prairie skippers and satyrids as well as the FWS candidate Speyeria idalia.
The transect was represented schematically on the reporting form by a series of vertical linear scales, each divided into 10 segments corresponding to the 10-meter flagged segments on the ground. The first of these scaled sections (0-100 meters) appeared on the left of the front of the form, and the remaining segments were shown directly on the back so that using the sheet one could "walk" through the transect and spatially envision each recorded encounter. Date, name of reporter, start time, finish time, temperature, estimated sunshine (10% increments), wind direction (eight points) and wind speed (Beaufort Scale) were all recorded at the finish of each transect walk. A separate reporting form was used for each transect walk.
For the checklist sampling method, a hypothetical list of regularly breeding resident species was first compiled for the Sheyenne National Grassland. This list was derived from formal records for all adjacent counties. Excluded were the majority of occasional, non-overwintering immigrant species. Native species for which it seemed likely that the absence of records represented incompleteness of information rather than actual absence were included in the hypothetical list and likewise in this list on the assumption that they will likely be confirmed at some time in the future. Date, name of reporter, location on the site, start and finish time, temperature, estimated percent sunshine (10% increments), wind direction (eight points) and wind speed (Beaufort Scale) were all recorded at the finish of each episode of checklist recording. A separate checklist reporting formwas used for each episode of checklist surveying.
Counting procedures for the two methods were identical in all respects except one, namely that in the transect method the recorder walked only along the marked transect route, whereas in the checklist method the recorder was free to wander at will. Protocols for counting and recording generally followed Pollard and Yates (1993), Monitoring Butterflies for Ecology and Conservation:
- The sampling day extended from approximately 9 am until not later than 8 pm.
- At the beginning of the day, a coin was flipped in order to determine which sampling method was to be employed first (heads = transect; tails = checklist); methods were thereafter alternated throughout the day.
- The appropriate method was then employed as follows:
- a) For the transect method, a single pass through the transect was recorded. Butterflies were mapped for location along the transect schematic on the form with encoded designations that were later translated to the standard four-letter acronyms used for database management.
- b) For the checklist method, up to 90 minutes of surveying were completed, after which the recorder began the transect method at the start of the next hour. In this method, butterflies were merely tallied in a blank provided next to the name on the checklist.
- In no case were voucher specimens collected within 100 meters of any point on the transect.
- The walking pace in both methods was steady and regular at approximately 35 meters per minute.
- Only butterflies actually seen within an estimated 2.5 meters on either side of the recorder, within 5 meters above the ground, and within 5 meters to the front were counted; butterflies behind the recorder or otherwise outside these limits were never counted.
- No active pursuit was allowed in either sampling method, and no effort was made to find or to see butterflies hidden from view or perched out of sight of the recorder.
- A net was carried, and when problem individuals could be netted without undue difficulty or active pursuit, they were netted and released after identification had been made (in such cases, counting was stopped until the walk was resumed).
- Where distinction between two alternative species was not possible, the commoner of the two options (for that period of the season and the site in question) was recorded.
- For each case involving more than two such alternatives, identification was made to the lowest confident taxonomic level practicable.
- When individuals flew ahead of the recorder, when the recorder was certain that they had already been counted, they were ignored; if the recorder was uncertain, they were counted.
These two methods were employed exclusively by the author on the following dates:
Table I. Summary of butterfly counts in the
Sheyenne National Grassland, Summer 1995
No. transect No. checklist
Date counts counts
18 May 0 1
12 June 5 4
13 June 5 5
25 June 4 2
26 June 4 6
2 July 2 3
31 July 2 3
1 Aug 5 4
16 Aug 4 3
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