Patterns of Occurrence from Spring Bird Counts at Oak Lake Field Station, Brookings County, South Dakota

Over 400 bird species have been recorded from South Dakota. Many of these birds simply pass through to other habitats. Others take residence seasonally while a few species are permanent residents. Recent studies suggest that spring migrants may be arriving earlier than previously recorded and these shifting migration times may be reflected in annual spring bird counts. The objective of this effort was to summarize patterns in bird occurrence from spring bird counts held at the Oak Lake Field Station, Brookings County, South Dakota (mid-May from 1995 to 2008). Tallies of bird species seen along a regular route were made over a period of 3-4 hours by groups of 4-15 individuals. Since 1994, 16 orders, 41 families, 110 genera and 168 species of birds have been recorded from formal observations at the station. During the period 1996-2000, 64 bird species were recorded during the spring bird counts (average = 29/yr). Accounts from the same route during the period 2004-2008 yielded 86 total species (average = 48/yr). The Jaccard Coefficient of similarity in occurrence between these two survey periods was 48.5%. Woodpeckers, swallows, wrens, gulls and terns were noted more frequently from later surveys. Consistently implemented spring tallies together with data on dates of first arrival and warmth sum accumulations may be useful in detecting early biotic effects from global climate change