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Platte River Status: An abundant migrant and common nesting species throughout the study area. Occurrence dates at the Mormon Island Crane Meadows, Hall County, range from 8 May to 10 September. Rosche (1979) recorded Northern orioles in the lower North Platte River Valley 14 May to 21 August.

Breeding Range: Locally common nesting species in the Platte River Valley west to Lake McConaughy, and in the Eastern Plain physiographic regions. Locally common to uncommon on the Dissected Plain and Western Plain regions. Highly local and uncommon on the Sandhills physiographic region. Short (1961) found "pure" Baltimore-type orioles at Hastings and Grand Island, and "pure" Bullock's-type orioles at Big Springs, Deuel County.

Breeding Population: The mean estimate of 56,000 breeding pairs made up about 2% of the nesting population in 1979-1980. Northern oriole ranked 17th in abundance among all species during the breeding season. Northern oriole was originally considered two species; Bullock's oriole was the western and Baltimore oriole the eastern forms. We found the Baltimore form commonly west to Ogallala on the South Platte River and Oshkosh on the North Platte River. Bullock's-type orioles occurred from about North Platte westward, but never approaching the abundance or frequency of the Baltimore form. Tout (1947) considered the Bullock's type rare in Lincoln County, whereas the Baltimore type was common wherever tall trees occurred.

Habitat: We found highest mean breeding densities in shelterbelt (157.7 pairs/km²), followed by lowland forest (42.0 pairs/km²), residential (19.7 pairs/km²), river channel island (6.2 pairs/km²), and upland native prairie (0.2 pairs/km²). The latter birds undoubtedly were foraging individuals recorded in native grasslands, rather than actual nesting individuals.

Effect of Habitat Alteration: De-watering of the Platte River system and the resultant increase in the distribution and abundance of forested vegetation has benefited northern orioles through encouraging the growth and development of mature lowland forest. Establishment of shelterbelts in agricultural areas has also proven beneficial as evidenced by the substantial nesting densities recorded there. Overgrazing of upland grasslands coupled with suppression of fires has contributed to expansion of forest growth suitable for Northern orioles in the western plains region.

Nesting Data: Five nests found on the Mormon Island Crane Meadows, Hall County, contained nestlings between 19 to 30 June 1984; the last fledgling departed the nest 3 July 1984. Tout (1947) reported a nest in North Platte on 13 June 1937. Egg dates in Kansas range from 11 May to 10 July (Johnsgard 1979). Rising (1974) reported egg dates in western Kansas between mid May and late June.