The developmental explanation for mobbing behavior is one that has been extensively studied in scientific literature. There is a clear scientific consensus that mobbing is a behavior that is learned through an individuals development and lifetime (Curio et al., 1978). This hypothesis, known as the 'cultural transmission hypothesis,' proposes that the perception of other birds mobbing an object/predator teaches an individual to fear that object and subsequently avoid it or mob it more strongly (Curio et al., 1978).
Curio et al. (1978) were able to test this developmental hypothesis directly by experimenting with captive jackdaws. In their experiment, an ‘observer’ bird was isolated but directly adjacent to a ‘teacher’ bird (the two birds were 1 m apart). A rotating box with 4 chambers was placed in between the birds so that two opposite chambers were either exposed to two birds or just one. A stuffed frairbird was used as the conditioned object, as it is novel, resembles no genuine blackbird predator, but is of a similar size to some of its actual predators. To condition the observer bird to mobb the frairbird, a stuffed owl was presented to the teacher at the very moment the rotation of the box revealed the frairbird. This was then followed by revealing empty chambers to the two birds. Curio et al. were able to substantiate the cultural transmission hypothesis: there was a statistically significant increase in response strength of the observer blackbird to the frairbird while the conspecific mobbed the owl compared to when the frairbird was shown without conspecific mobbing (p = 0.001) (Figure 2). This experiment demonstrates that the ‘nongenetic transfer of information’ functions to increase the fitness of the observer (Curio et al., 1978). While this research was done almost 40 years ago, this seminal finding nonetheless substantiates developmental aspects of mobbing behavior.
Curio et al. (1978) were able to test this developmental hypothesis directly by experimenting with captive jackdaws. In their experiment, an ‘observer’ bird was isolated but directly adjacent to a ‘teacher’ bird (the two birds were 1 m apart). A rotating box with 4 chambers was placed in between the birds so that two opposite chambers were either exposed to two birds or just one. A stuffed frairbird was used as the conditioned object, as it is novel, resembles no genuine blackbird predator, but is of a similar size to some of its actual predators. To condition the observer bird to mobb the frairbird, a stuffed owl was presented to the teacher at the very moment the rotation of the box revealed the frairbird. This was then followed by revealing empty chambers to the two birds. Curio et al. were able to substantiate the cultural transmission hypothesis: there was a statistically significant increase in response strength of the observer blackbird to the frairbird while the conspecific mobbed the owl compared to when the frairbird was shown without conspecific mobbing (p = 0.001) (Figure 2). This experiment demonstrates that the ‘nongenetic transfer of information’ functions to increase the fitness of the observer (Curio et al., 1978). While this research was done almost 40 years ago, this seminal finding nonetheless substantiates developmental aspects of mobbing behavior.
Figure 2. The strength of mobbing a honeyeater (stuffed bird conditioned to be mobbed). In Experiment 1, the honeyeater was show to an observer blackbird (no history of mobbing) while a conspecific blackbird mobbed an owl; in Experiment 2, the honeyeater was shown without conspecific mobbing; in Experiment 3, nothing was show (acts as a control). From these results it is clear that the response strength of an observer blackbird is influenced by conspecific mobbing (p < 0.001) - i.e., this behavior is one that is learned. Taken from Curio et al., 1978.
This hypothesis has been recently examined in American crows, chickadees, marmosets, and meerkats (Graw and Manser, 2006; Clara et al., 2008; Nolen and Lucas, 2009; Cornell et al., 2012).