ILLINOIS AUDUBON BULLETIN 31 
Nesting Trends and Habits of Northern Harriers at 
Goose Lake Prairie, Grundy County 
by DALE E. BIRKENHOLZ 
Since the preservation of Goose Lake Prairie in 1969, one of the 
memorable parts of the nesting season has been the frequent nesting of 
Northern Harriers (Circus cyaneus). Rather complete bird nesting surveys 
from 1971 through 1973 (Birkenholz 1972, 1973) and less intensive, but 
regular observations since that time have provided a six-year record of the 
species. This note summarizes the species’ status for this period and also 
reports on some facets of its nesting behavior. 
Nesting Trends 
A nest was first found in June 1971 at the southwest corner of Block 7 
(See Birkenholz 1973, 1975). Details of its success were reported earlier 
(Birkenholz 1975). In 1972 no birds nested on the preserve, but a male was 
seen foraging occasionally along the east border, in Blocks 6 and 8. | 
assumed that a nest might have been located east of the preserve where 
suitable habitat exists. In 1973, two pairs of harriers nested on the preserve. 
One nest was located at the site of the 1971 nest. The other was located one 
mile north-northwest, near the northwest corner of Block 5. 
In 1974 and 1975, again no birds nested. On two occasions in 1974 a 
male was seen over Blocks 8 and 10, and once it disappeared toward the 
east. Hamerstrom and De La Ronde Wilde (1973) reported daily cruising 
areas of Wisconsin harriers to be 1% x 2%4 miles, hence this bird might well 
have been nesting east of the preserve. In 1976 two pairs nested, both in 
Block 5. These nests were located about 150 yards apart, both approxi- 
mately 200 yards south of the location of the 1973 nest. Brown and Amadon 
(1968) reported that the same general area often is reused year after year by 
this species. 
Social Behavior 
From 1971 to 1975, nesting harriers were monogamous and, when two 
nests were present, no overlap in hunting areas was observed. In 1973, the 
pair in Block 5 hunted into Blocks 2 and 7; the pair in Block 7 hunted into 
Blocks 8, 9, and 10 and the area west of Block 7. 
In 1976, the two nests in Block 5 were no more than 150 yards apart, 
but no overlap of hunting areas was observed. The male from the west nest 
hunted mostly over Block 2, while the male from the east nest confined his 
hunting activities to the east, in Blocks 3 and 6 and perhaps even further. 
Errington (1930) reported three grouped nests but stated that the respective 
