The Accuracy of Fixed-Wing Aerial Surveys of Feral Horses on a Coastal Barrier Island

Abstract

An aerial census of feral horses on Assateague Island National Seashore was compared to a comprehensive ground count during April of 1988. Three low-level fixed-wing Rights resulted in a mean count of 125 horses, while the ground census produced 147 horses. The census was subdivided among three sections of the island with differing types and amounts of vegetation, and aerial counts decreased in accuracy from a high of 97.7% of the ground count at the north end of the island where woodland and shrub-succession vegetation was minimal to a low of 60.8 % at the southern end of the island, where these two vegetation types were more common and abundant. Two additional aerial counts conducted in June after vegetation leafed out resulted in a significant decrease in accuracy. The correction factor for the three April aerial counts ranged from 1.0 in the north to 1.4 in the south, with a mean of 1.17 overall.