SREL Reprint #0009

 

 

 

The Use of Mist Nets in Population Studies of Winter Fringillids on the AEC Savannah River Area

 

E. P. Odum and G. L. Hight

 

 

Summary
1. Winter fringillids inhabiting the abandoned fields of the AEC Savannah River Plant area may be divided into two ecologic groups: “herb sparrows” and “bush sparrows.”  Japanese mist nets proved effective for sampling populations of the former group which consisted of the abundant Savannah Sparrow and the less common Vesper Sparrow, Grasshopper Sparrow and LeConte Sparrow.

2. About 1600 “herb sparrows” were banded during a three-winter period, 1955-57, over 1000 of these in a single large field which was intensively studied during successive years; about 100 repeats and 112 returns were recorded in this field.

3.The dominant species, Savannah Sparrow, was found in both “forby” and “grassy” fields with both dense and sparse cover while the less common species exhibited distinct habitat preferences resulting in different proportions of species in different areas.  On the intraspecific level there was no evidence that the five subspecies of Savannah Sparrow (which breed in widely different geographical areas) were segregated into different habitats during the winter.

4. In the intensively studied field, No. 3-412, LeConte Sparrows were present only in 1955 and Savannah Sparrows increased somewhat in numbers in 1956 and 1957 as indicated by rate-of-capture indices and marking-recapture estimates.

5. Density estimates with appropriate confidence limits were calculated for 3-412 and one other area by the use of marking-recapture ratios, and the results in 3-412 checked with strip and quadrant counts made by Dr. Norris with reasonable agreement resulting.  In a small five-acre area of concentrated food in a “Carolina Bay” 1200 birds wintered, while about 1000 birds were estimated to utilize about 100 acres of field 3-412.  In the latter area birds concentrated their activities in a center portion where crabgrass was most common.

6. “True return” percentage as calculated from the actual number of returns and the estimated size of population “in contact with nets” was 38% in 1956, 41% in 1956 and 26% for the two-year span, 1955-57.  Thus, out of 100 birds wintering about 40 returned the next year and 26 of these survived to the third winter.

 

 

Odum, E.P. and G.L. Hight. 1957. The use of mist nets in population studies of winter fringillids on the AEC Savannah River Area. Bird-Banding 28:203-213.

 

 

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