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Platte River Status: A fairly common migrant and nesting species throughout the study area. Occurrence dates at the Mormon Island Crane Meadows, Hall County, range from 11 May to 14 August. Tout (1947) considered Bell's vireo a common nesting species in Lincoln County, present 8 May to 19 September. Bell's vireo is present in the lower North Platte River Valley 14 May to 2 September (Rosche 1979).

Breeding Range: Locally common in the Platte River Valley physiographic region; uncommon and local on the Eastern Plain and Dissected Plain; rare on the Western Plain and in the Sandhills. Short (1961) found Bell's vireo commonly along the Platte and South Platte rivers from Elm Creek west to Colorado.

Breeding Population: The population in 1979-1980 was estimated at 7,000 breeding pairs which made up about 0.2% of the total bird number on the study area. Our data suggest that Bell's vireo was the most numerous vireo nesting in the Platte River Valley those years.

Habitat: We found the largest mean breeding density in river channel island (27.0 pairs/km²), followed by lowland forest (2.2 pairs/km²), and upland prairie (0.1 pairs/km²). Tout (1947) reported that Bell's vireo in Lincoln County was found in streamside thickets (willow growth on river channel islands) and in adjacent canyonlands. Rising (1974) found that breeding densities of Bell's vireo were greatest along the Cimarron River in southwestern Kansas in deciduous thickets of Prunus sp., willow, and salt cedar.

Effect of Habitat Alteration: Bell's vireo has benefited from de-watering of the Platte River system and the subsequent encroachment of wooded vegetation within the river channel. The overwhelming abundance of this species in willow growth on river channel islands, along with their apparent exclusion from mature wooded habitats suggests that early successional stage vegetation within the channels is of considerable importance to this species.

Nesting Data: We have found eight nests containing an average of 2.8 eggs within the study area. Tout (1947) reported that among 17 Bell's vireo nests found in Lincoln County, egg dates ranged from 28 May to 19 June; mean clutch size was 2.6 eggs. Rising (1974) speculated that nest parasitism by brown-headed cowbirds was probably common in southwestern Kansas. Johnsgard (1979) reported that egg dates in Kansas ranged from 1 May to 20 July.