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, 106 (22), 8959-62

Urban Mockingbirds Quickly Learn to Identify Individual Humans

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Urban Mockingbirds Quickly Learn to Identify Individual Humans

Douglas J Levey et al. Proc Natl Acad Sci U S A.

Abstract

Practically all animals are affected by humans, especially in urban areas. Although most species respond negatively to urbanization, some thrive in human-dominated settings. A central question in urban ecology is why some species adapt well to the presence of humans and others do not. We show that Northern Mockingbirds (Mimus polyglottos) nesting on the campus of a large university rapidly learn to assess the level of threat posed by different humans, and to respond accordingly. In a controlled experiment, we found that as the same human approached and threatened a nest on 4 successive days, mockingbirds flushed from their nest at increasingly greater distances from that human. A different human approaching and threatening the nest identically on the fifth day elicited the same response as the first human on the first day. Likewise, alarm calls and attack flights increased from days 1-4 with the first human, and decreased on day 5 with the second human. These results demonstrate a remarkable ability of a passerine bird to distinguish one human from thousands of others. Also, mockingbirds learned to identify individual humans extraordinarily quickly: after only 2 30-s exposures of the human at the nest. More generally, the varying responses of mockingbirds to intruders suggests behavioral flexibility and a keen awareness of different levels of threat posed by individuals of another species: traits that may predispose mockingbirds and other species of urban wildlife to successful exploitation of human-dominated environments.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Responses (means ± SEM) of incubating mockingbirds to intruders approaching the nest on 5 consecutive days. Black points and lines show responses to the same intruder over the first 4 days; gray points and lines show responses to a novel intruder (control) on the fifth day. Asterisks indicate significant differences (P < 0.05) between indicated day and first day.
Fig. 2.
Fig. 2.
Distance from approaching intruder at which incubating mockingbirds flushed from their nest as a function of number of pedestrians per hour that pass within 5 m of the nest (slope = −0.4; t22 = −2.2; P = 0.036). Points show average flush distance (± SEM) for each incubating bird over the 5 days of the experiment. The fitted line represents the effect of pedestrians on the flush distance on the third day of the experiment. The negative relationship remains significant if the 2 right-most points are removed (slope = −0.1; t20 = −2.7; P = 0.014). Birds nesting near busy sidewalks are more tolerant of humans, yet still respond strongly to repeated visits by the same human (Fig. 1).

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