Ferruginous and Swainson's Hawk Abundance and Distribution in Relation to Land Use in Southeastern Alberta

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Abstract
Eighty 41-km2 (4.4% of total area) sample plots were selected at random in a 74,686-km2 area in southeastern Alberta and searched for nesting ferruginous (B. regalis) and Swainson''s hawks (B. swainsoni). The estimated number of nesting ferruginous hawks was 1082 pairs (.+-. 429) and the number of Swainson''s hawks 3879 pairs (.+-. 802). Ferruginous, but not Swainson''s, hawks declined in abundance as the proportion of land under cultivation increased. Swainson''s hawks nested in close proximity to human habitation; ferruginous hawks did not. The abundance of ferruginous hawks may be limited by the availability of grassland habitat, or by the survival of the hawks with only preferred habitat types occupied. The size and number of plots sampled was more than adequate to minimize sample variance but confidence intervals were wide because only 4.4% of the total area was sampled.