Seasonal Trends in Summer Diet of the Lapland Longspur near Barrow, Alaska

Custer, Thomas; Pitelka, Frank

Contents of Lapland Longspur stomachs and esophagi were sampled near Barrow, Alaska, from May to August, in 1969, 1971, 1972, and 1973. Data from stomach contents were corrected for differential digestion of prey items. Longspurs shift seasonally from larval to adult arthropods and back to larvae, responding to changes in the abundance of these prey items. Seeds are a vital supplementary food in late May and August, when arthropods are scarce or inaccessible. One species of crane fly is the major dietary component for longspurs during June and July. Its high abundance and substantial dry weight per individual may contribute to the success of longspurs at Barrow. The diets of longspurs and four common shorebirds (Calidris spp.) at Barrow are similar in the range of prey items taken except for seeds and tenthredinid larvae. Their diets overlap closely when feeding sites are restricted because of snow and surface water (chiefly at the beginning of the season) and when prey is abundant in early and mid-July. Competition is possible early in the season but unlikely in July when surface insects are superabundant. In addition to exclusive fractions of diet, habitat separation and the advantages of fringillid form apparently contribute to the success of longspurs in a tundra community of insectivores dominated by shorebirds.

Seasonal Trends in Summer Diet of the Lapland Longspur near Barrow, Alaska

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