Kevin D. Downs and Stanley H. Anderson, Wyoming Cooperative Fish and Wildlife Research Unit, University of Wyoming, Box 3166, University Station, Laramie, WY 82071
Common snipe (Gallinago gallinago delicata) numbers in North America are unknown, no survey technique to monitor their numbers has been developed and doubts exist about using the Breeding Bird Survey (BBS) to monitor snipe trends. In order to help solve these problems, this research project focused on four major objectives: (1) evaluate existing labor intensive techniques such as tape playback, territorial mapping, territorial/spot mapping, flush counts and nest searches; (2) develop and evaluate indices (call, winnow and call/winnow counts) that could monitor snipe numbers on a continental scale; (3) identify important habitat characteristics; (4) evaluate the effectiveness of the BBS for common snipe. Four labor intensive techniques were evaluated for effectively estimating the number of snipe or territories. Territorial/spot mapping was found to be the most effective technique because the results obtained accurately represented the number of territories present. Flush counts were the second best technique because they did not accurately estimate the number of snipe present in all snipe habitats. Flush counts worked best in long narrow strip habitats that could be easily covered by a few people. In large continuous habitats flush counts did not accurately estimate snipe numbers because snipe were harder to flush. Tape playback territorial mapping and nest searches did not accurately estimate snipe numbers due to varying snipe responses and difficulty in finding nests. An index that counts the number of different calling and winnowing snipe heard most accurately monitored snipe numbers because the probability of detection, percentage of snipe detected and the estimate of snipe numbers was the greatest, most consistent and most accurate. The index should be conducted during the 20 day time period before snipe begin to incubate and after the arrival of females. This 20 day time period usually falls after the full moon in April and before the first quarter in May. Transects should be established in the habitat with points spaced 1 km apart. A minimum of seven points should be used to conducts surveys from in order to obtain good results. The survey is conducted at dusk approximately 5 minutes after most of the snipe become active and should be discontinued when snipe cease or decrease activity. The survey period is short (only usually lasts 30-45 minutes), so only 3 points or less may be surveyed in one night. Each point should be visited at least 3 times during the 20 day time period. There are six factors (season, time of day, lunar cycle, wind speed, solar radiation, and temperature) that effect snipe winnowing and calling and should be considered or at least measured when conducting snipe surveys. Driving roads the season prior to actual surveying will help identify possible snipe areas. Those areas should also be searched for snipe nests the season prior to surveying, in order to have good phenological information about the snipe area in question, which will help identify appropriate survey times the following season. Surveyors should be standardized prior to conducting actual surveys if more than one surveyor is used. For more detailed information about surveying for snipe refer to Downs (1998). From our results, we identified four important characteristics (distance to nearest shrubby cover, water depth, soil moisture, the dominance of sedges and sedge heights) and used them to construct a ranking criteria for categorizing snipe habitats. We found the BBS is not conducted at the right time of day nor does it consider the variables (season, lunar phase, solar radiation and temperature) that affect snipe activity to be effective in detecting snipe trends. As a result, the numbers of snipe the BBS detects is low and the snipe activity detected could be related to nest success more than abundance. A final report by Masters candidate Kevin D. Downs will be completed during the spring of 1998. These results are from the last year of a 3-year study funded by the 1995 Webless Migratory Game Bird Research Program (U.S. Fish and Wildlife Service and the U.S. Geological Survey-Biological Resources Division), U.S. Fish and Wildlife Service (Migratory Bird Management Office), Wyoming Game and Fish Department and the Wyoming Cooperative Fish and Wildlife Research Unit.
Downs, K. D. 1998. Common snipe surveys, habitat and evaluation of the breeding bird survey. M.S. thesis, University of Wyoming, Laramie. 91pp.