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Platte River Status: An abundant migrant and nesting species; occasional winter resident. Tout (1947) described enormous flocks of common grackles in Lincoln County, stating that common grackle flocks were the largest of any bird species present there. Rosche (1979) reported common grackles in the lower Platte River Valley during 24 March to 6 November.

Breeding Range: Common grackle is especially numerous and well-distributed in the Dissected Plain, Eastern Plain and Platte River Valley physiographic regions. Their abundance here probably relates to the presence of extensive areas of agricultural land along with livestock feedlots that are exploited for foraging. In the Sandhills and Western Plain physiographic regions, common grackles are less numerous, and their distribution is more spotty than in areas further east.

Breeding Population: Common grackles ranked second in abundance among all species with an estimated mean population of 251,000 breeding pairs in 1979-80. Their breeding population made up 8.5% of the total number of breeding birds in the study area at that time. Because of the difficulties inherent in sampling colonial nesting bird populations, we believe our estimates are minimums.

Habitat: The common grackle has adapted well to the changes in the landscape brought on by the advance agricultural development in the Platte River Valley. We found highest mean breeding densities in shelterbelts (455.7 pairs/km²), followed by residential habitats (88.0 pairs/km²), river channel island (46.0 pairs/km²), lowland forest (26.7 pairs/km²), alfalfa (7.2 pairs/km²), domestic hayland (5.2 pairs/km²), wet prairie (4.0 pairs/km²), upland prairie (2.0 pairs/km²), corn (1.7 pairs/km²), and wheat (0.5 pairs/km²). Rising (1974) reported common grackles as a common summer resident near water in western Kansas, and found the largest number of breeding birds in the northwestern corner of that state.

Effect of Habitat Alteration: The positive response to the presence of large breeding densities in shelterbelts and residential habitats is indicative of the benefit that common grackles have obtained from the extensive alteration of native habitats in the study area. The practical exclusion of this species from such habitats as wet prairie and upland prairie suggests that during pristine times, the common grackle was probably a rare and local nesting species in the study area. Graber and Graber (1963) speculated that the habitats, particularly in northern Illinois, would contribute to future population increases in that state.

Nesting Data: Our records indicate that the peak of nesting season is during 15 May to 15 June. Common grackles are highly synchronous in their nesting activities (Faanes 1976), thus virtually all pairs in a colony are at the same stage of the nesting cycle during the same time period. Mean clutch size among 6 nests in Lincoln County was 2.8 eggs during 6 May to 19 June. Egg dates from Kansas range from 11 April to 30 June with peak activity in May (Johnsgard 1979).