Determining Impact on Least Tern (Sternula antillarum) Breeding Colonies Along a Gradient of Human Disturbance
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Populations of seabirds and shorebirds are in steep decline. This includes the beach-nesting least tern (<i>Sternula antillarum</i>), which has decreased in number. This study examines the impacts of human disturbance as a possible cause of the decrease. Human disturbance was measured at ten colonies in southwest Florida by observing flushing of terns from their nests in response to different degrees of disturbance. I recorded all disturbance events during my observation periods, as well as the distance of any disturbance from the colony. The colonies were divided into 15 m sections to compare impacts of disturbance on core versus peripheral parts of the colony. Intercept surveys were conducted to assess attitudes and determine why people use the beach, if people value the birds, if people know of possible harm they can cause the birds, and if people might be willing to change their behavior. Different categories of disturbance included human, dog, crow, gull, other, and unknown. The different categories of disturbance events were significantly different in terms of percent of colony flushed and time spent away from the nest, with dogs and crows causing the largest response. There was no significant difference in the measure of response for the core versus peripheral parts of the colony, nor was there a significant correlation between the degree of disturbance and nesting success. Crow disturbances were typically at sites where trash was common on the beach. Responses to the surveys indicated that those surveyed valued the birds, but were not aware of negative impacts on them. Furthermore, people were not generally willing to change their behavior even if it meant more protection for the least tern. These results suggest keeping dogs away from the beach would benefit least terns, and it would benefit them to take action to deter crows from nesting areas.