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Platte River Status: A common migrant and nesting species across the study area. Dates of occurrence at the Mormon Island Crane Meadows, Hall County, range from 22 April to 22 September. Tout (1947) considered brown thrasher a common nesting species in Lincoln County, present 23 April to 25 November. Rosche (1979) recorded this species in the lower North Platte River Valley 6 May to 11 September.

Breeding Range: A common and widely distributed nesting species in the Platte River Valley and Eastern Plain; fairly common on the Dissected Plain; uncommon and local in the Sandhills. Brown thrasher is apparently absent from much of the canyon region of the Dissected Plain in southern Lincoln County.

Breeding Population: The population was estimated at 26,000 nesting pairs in 1979-1980. Brown thrasher made up nearly 1% of the total breeding bird numbers in the study area those years.

Habitat: We found the largest mean nesting density in shelterbelt (84.7 pairs/km²), followed by river channel island (8.7 pairs/km²), lowland forest (8.0 pairs/km²), residential (6.0 pairs/km²), domestic hayland (0.5 pairs), upland prairie (0.5 pairs/km²), alfalfa (0.2 pairs/km²), and wet prairie (0.2 pairs/km²). Brown thrasher makes extensive use of edge habitats on the study area including field borders and fence rows. Brown thrashers use a variety of habitat types, but highest densities are typically associated with hedgerows (Graber et al. 1970), forest edge (Stauffer and Best 1980), or mid-successional stage forests (Back 1979; Graber et al. 1970; Willson 1974). Faanes (1982) found brown thrasher on a central North Dakota study area most commonly in prairie thickets and in portions of shelterbelts supporting a dense shrub layer. Rising (1974) recorded brown thrasher in western Kansas primarily in rank riparian brush, where nests were usually placed in understory vegetation. Faanes (1983) found brown thrasher a fairly common nesting species in western North Dakota wooded habitats supporting high numbers of young trees, high shrub density, and low percent canopy cover. Graber and Graber (1963) found that hedgerows with a mean density of 471.7 birds per km² supported the largest brown thrasher population in central Illinois.

Effect of Habitat Alteration: Brown thrasher has benefited from the alteration of several habitat types on the study area, including the establishment of shelterbelts in areas previously supporting native grasslands. Excessive grazing of the understory in the riparian zone, and the continuous removal of brushy fence rows to accommodate expanding field sizes, pose the two greatest threats to this species during the nesting season in the Platte River Valley.

Nesting Data: We have located six active nests on the Mormon Island Crane Meadows during 4 to 25 June. Nestlings have been observed in nests there 14 June to 1 July. Fledged young were observed as early as 10 June 1984. Tout (1947) reported that mean clutch size among 35 nests in Lincoln County was 3.3 eggs. Lincoln County egg dates extend from 21 May to 17 July. Collister (1950) found one pair nesting in a lilac bush and another in Virginia Creeper near Brady, Lincoln County in 1949. Egg dates in Kansas extend from 1 May to 20 July (Johnsgard 1979).