Breeding Bird Distribution and Abundance in the Barren Islands, Alaska

Abstract

Tidal currents of considerable velocity occur in the Barren Islands with the flood current setting approximately northwestward and the ebb southeastward (U.S. Coast and Geodetic Survey 1964). Severe tide rips and strong winds occur in the vicinity of the islands and are frequently dangerous for small vessels. The wind and ocean currents among the islands are usually much stronger than a few miles away. Tide rips produce upwellings where food for marine birds and mammals is more readily available. Slack waters do not occur in the Barrens at the change of tides, and tidal vicissitudes exceed 20 feet at certain times of the year. Although Homer is only 55 miles from the Barren Islands, the climate in the Barrens is probably more similar to that of Kodiak, 80 miles distant. Homer is in the lee of the Kenai Mountains and thus receives an average of only 23.06 inches of precipitation compared to 56.71 inches per year in Kodiak. The annual mean temperature for the Barren Islands is probably about 40°F, as annual means for Kodiak and Homer are 40.7 F and 36.5 F, respectively. The annual mean wind velocity in the Barrens is surely considerably higher than that of Kodiak where it is 10.1 mph. The prevailing wind direction most of the year is northwest in Kodiak and northeast in Homer. Cloud cover, mainly fog, is most extensive in the Barren Islands region during spring and summer. Sky obscuration in Kodiak ranges from an average of 61 percent in January to 84 percent in May. Beach plant communities in the Barren Islands are composed mainly of Elymus arenarius mollis, Honckenya peploides, Mertensia maritima, Lathyrus maritimus, and Senecio