Hourly Variation in Morning Point Counts of Birds

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Abstract
We studied hourly variation in measures of the abundance of individual species and the species composition of bird assemblages in different habitats and seasons in the western Sierra Nevada of California, using 8- and 10-min point counts. Results failed to show clearly that any one of the first 4-5 h after sunrise is better than another. The advantages of more counts or more sites sampled, or both, gained by counting over several hours outweigh any advantage that might result from restricting counts to periods that give counts with lower variance. Species richness was better measured by sampling over a period of several hours than by sampling an equal period of time during any single hour.