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Platte River Status: A regular migrant and nesting species. Occurrence dates at the Mormon Island Crane Meadows, Hall County, are 16 May to 9 October. Tout (1947) considered the dickcissel a common nesting species in Lincoln County, present during 15 May to 11 September.

Breeding Range: An abundant nesting species in the Eastern Plain, Dissected Plain, and in the Platte River Valley physiographic region west through Dawson County. Dickcissel distribution becomes spotty west of Dawson County, at approximately the 100o W longitude meridian. Dickcissel was reported as a summer resident near Omaha Beach on Lake McConaugh, Keith County, and along the North Platte River near Ash Hollow, Garden County in 1977 and 1978, but not in 1979 (Rosche 1979). Tout (1947) considered the dickcissel common on Platte River Valley farmland in Lincoln County, but not common in the Sandhills. Short (1961) found dickcissel commonly throughout the area west to Crook, Colorado.

Breeding Population: The estimated population in 1979-1980 was 69,500 pairs, which made up 2.3% of the breeding bird numbers in the study area. The polygynous mating system of the dickcissel suggests that our population figures are minimums. Fretwell (1977) reported that some male dickcissels may be mated with up to 8 females.

Habitat: A characteristic breeding bird of agricultural habitats and roadsides, we found dickcissel occupying most of the non-forested habitats in the study area. Highest mean breeding densities were in alfalfa (13.5 pairs/km²), followed by domestic hayland (8.7 pairs/km²), wet prairie (4.0 pairs/km²), wetland (3.5 pairs/km²), upland prairie (3.2 pairs/km²), lowland forest (1.0 pairs/km²), corn (0.7 pairs/km²), river channel island (0.5 pairs/km²), and wheat (0.2 pairs/km²). Stewart (1975) considered dickcissel especially characteristic of alfalfa in North Dakota. Von Steen (1965) reported that 60% of the dickcissel nests on his Phelps County study area were in wild rose and alfalfa; 10% of the nests were in smooth brome, summer cypress, wild lettuce and smartweed. Aspects of the polygynous mating system of the dickcissel may be related to habitat suitability. Zimmerman (1966) and Martin (1970) found forb coverage in fields was important to mating success. Harmeson (1974) found that the frequency of major forb species in fields was greater for bigamist territories than for monogamous or bachelor territories. Zimmerman (1971) found a positive correlation between the volume of vegetation and the number of mates acquired. Zimmerman also concluded that only at high male breeding densities were some males forced to include less suitable habitat in their territories. Von Steen (1965) observed that 60% of the dickcissel nests found at the Sacremento-Wilcox Wildlife Area, Phelps County were in wild rose and alfalfa. Smooth brome, fireweed, wild lettuce, and smartweed were each used by 10% of the nests.

Effect of Habitat Alteration: Dickcissels appear to have benefited by conversion of native grasslands to agricultural crops especially alfalfa fields. Most studies of dickcissel habitat use have shown overwhelming preference for hayland and native grassland. Hayfields in the Platte River Valley appear, at least outwardly, to be beneficial to dickcissel. However, alfalfa is a harvested cash crop, with three or four cuttings each summer. The continuous removal of nesting cover by farming operations must be having a negative impact on dickcissel nesting success. Parasitism by brown-headed cowbirds has a profound impact on dickcissel nesting success (Zimmerman 1966, 1971). Fretwell (1977) reported that mid June was a relatively safe period for nesting, falling between periods of cowbird parasitism and nest predation. However, mid June is a period of intensive alfalfa harvest in the Platte Valley. We have noticed an absence of dickcissels in wet prairie habitat on the Mormon Island Crane Meadows, Hall County, in early June, but a general influx to wet prairie after the alfalfa harvest intensifies in mid June. Our observations suggest that although dickcissels appear to prefer hayfield habitat to attempt nesting, after the vegetation has been removed, and nesting ceases, the birds move to native wet meadows to re-establish nesting territories. Thus, the remaining wet prairie habitat along the Platte River may serve as important refuge if this species is to nest successfully in the valley. This hypothesis also suggests, that encroachment of wooded vegetation on wet prairie will exert a negative impact on dickcissel numbers.

Nesting Data: Egg dates at the Mormon Island Crane Meadows, Hall County, are 23 June to 18 July. The latter was probably a renesting. Dickcissel often builds the first nest in alfalfa which usually is destroyed by crop harvesting machinery before the young fledge. Under these circumstances they will renest in adjacent areas which normally are grazed by livestock. Three of five dickcissel nests we have found on Mormon Island were parasitized by brown-headed cowbirds. Von Steen (1965) located eight dickcissel nests at the Sacramento - Wilcox Game Management Area, Phelps County during 15 to 25 June 1963. The nests contained 25 dickcissel eggs and 19 brown-headed cowbird eggs; hatching success was 24% and 34%, respectively. The mean nest height above the ground was 34.3 cm. Johnsgard (1979) reported that Kansas egg dates extend from 1 May to 10 July.