In March 1998, we began locating and marking the intersection points. A map provided by base headquarters provided a scale with which we could measure our grid intervals. A starting point was chosen from this map, and grid lines drawn. In the field, a two-person team used a measuring tape and a compass to walk a magnetic course for a distance of 250 m from the chosen starting point. At the end point, the map was checked to verify that the location was correct by referencing recognizable landmarks such as fence lines, road intersections, and prominent tree stands. (The topography of the area was relatively flat with minor elevation changes arranged in ridges oriented north and south. Using a two dimensional approach resulted in some degree of distortion of actual ground distance between points, but we always maintained a minimum ground distance of 250 m.) A wood stake with a plastic identification tag was placed at each intersection point. The tag was labeled with the point’s (x, y) coordinates, with the (1, 1) point occurring in the southwest corner of the grid. A non-differentially corrected GPS fix was obtained for each point and written on the identification tag. Subsequent checks with an independent differentially corrected receiver showed that the accuracy of the original unit was acceptable with agreement to 0.05 minutes latitude/longitude.
Birds Point Counts Avian point counts were conducted at 90 grid intersections after the methods of Reynolds et al. (1980), Freemark and Rodgers (1995), and Ralph et al. (1995). The objective of the avian point count was to record all birds observed visually and aurally from a stationary position during specified hours. Several grid intersections occurred in areas inaccessible or inappropriate for conducting a point count, such as the middle of a lake or in a building. When this occurred, the point was relocated to the nearest suitable location, where the count and measurement of habitat variables were conducted. In all cases, the point of actual intersection could be observed from the displaced point. Each sample point was visited once during the first four hours of daylight beginning in late April 1998. Upon arrival at each point, a minimum of three minutes elapsed for acclimation prior to a five minute observation period. During acclimation, a field data form was prepared. For each avian observation, a bearing and range were estimated. In addition, any non-avian observations were recorded as incidentals on a separate section of the data sheet. Transit times between points averaged 12 minutes. Thus to remain within the allotted four hours of observation, we sampled 8-11 points each day. Point counts were conducted by lone individuals. Observers were experienced in field identification, and supplemented their background with study of tape-recorded bird songs and numerous field guides. Prior to the breeding season point counts, several sessions of general reconnaissance were conducted to familiarize the observers with species expected at the site. Point counts were repeated in December 1998 and early January 1999 to characterize wintering species diversity and abundance. The winter count was not time constrained as was the breeding count, but was restricted to periods when observations were not compromised by the weather. The point count was designed for passerines, but all birds observed were recorded. Additional survey methods concentrated on other avian orders.
Waterfowl Surveys Camp Rilea’s lakes, creeks, and certain wetlands were surveyed for waterfowl twice per month from late January through May 1998 and from September 1998 through March 1999. A field data form was prepared for each location. Surveys were conducted on foot and from vehicles. Observations were made using binoculars and a spotting scope. On occasion, multiple waterfowl surveys were conducted over two to three days, and a composite data form was prepared. Information on species diversity was totaled in the composite, while the number for each individual species was recorded as the highest number observed for any single observation. These composite waterfowl inventories enabled us to document species that may have been missed on a single day. In May, an inspection was conducted of nest boxes already in place along both East and West Neacoxie Creek. Boxes were accessed by foot and by boat, and inspection accomplished by using an extension ladder. Nest status and species occupancy were recorded.
Shorebird Surveys The area of open beach west of the foredune to approximately 100 m out into the breakers was treated as one linear unit and surveyed for shorebirds and other species independently from other surveys. All grid intersections in the open beach area were ignored. Surveys were conducted on foot and by vehicle, using binoculars, a spotting scope, and hand-held counters to identify and count species. Foot surveys were designed to target shorebirds inhabiting the interface between the high tide line and the vegetation of the foredune. Vehicle surveys were accomplished by driving the high tide line slowly in two directions. Emphasis was directed toward the surf line when traveling in one direction, and toward the vegetation interface on the return trip. Relative abundance by species was recorded by direct observation, and general activity noted. When flocks were moving up and down the beach, care was taken to only count birds once. Though listed as a shorebird survey, all species were recorded, including passerines, waterfowl, raptors, etc. Surveys began in late January 1998 and continued through early March 1999. During spring and fall, at least two surveys were conducted per month to increase detection of transient species. As with waterfowl, occasionally a composite survey of shorebirds was conducted over two to three consecutive days. A field data form was prepared for each survey period. Human/pet activity observed on the beach was also recorded after it became apparent that disturbance was highly variable day to day.
Incidental Observations Incidental avian observations were recorded throughout the study. Given the large amount of field time involved in tasks such as measuring habitat variables and small mammal trapping, a considerable amount of additional information was collected on many species.