Mobbing of the top predator: a correlation between avian community richness and the number of mobbing species

Abstract

Mobbing is an anti-predator strategy initiated by one or more members of prey species aiming at driving away a predator that is not undertaking an attack. Because of a continuous dispute as to whether mobbing of a top predator may indicate species richness, we tested the correlation between the number of species engaging in mobbing and avian community richness. In the boreal forest of central Norway, we conducted a series of 83 bird census trials in 2014 and 2015. Each census trial consisted of two 5-min phases. In the first phase an ordinary point count was performed as a control; in the immediately following second phase either a stuffed Eagle Owl or Capercaillie female decoy was presented to study mobbing of a top avian predator and non-predatory species. Mobbing was more likely to occur, and the number of species that engaged in mobbing was higher, in habitats richer of bird species. Our study showed that the cumulative effects of being mobbed increase with richness of the local avian community. We did not find any support for the notion that mobbing is triggered by mobbing activity of the two most active and abundant species. No support was provided for an assertion that using an owl decoy would result in higher number of detected species during a census. Our study urges the need for identification and quantification of costs of mobbing for an avian predator.

Anything for a quiet life: shelter from mobbers drives reproductive success in a top‐level avian predator

“…More research is needed to quantify bird functions and services in agrarian systems as well as evaluate their effectiveness and economic value (Wenny et al 2011). Our findings suggest that mobbing, an anti-predator strategy seen mostly in birds (Caro 2005, Pawlak et al 2019, can be a research avenue for bird services, and that avian mobbers can be exploited to protect some sensitive domestic prey from raptor attacks.…”

Mobbing in animals: A thorough review and proposed future directions

“…These shortcomings inflate the occurrence of false negatives, for example, the number of species that are classified as non-mobbers when, in fact, the conditions were not ones in which a focal species mobs (e.g., the type of predator used, time of year, degree of cover). Thus, studies conducted during a single season risk excluding any species that mob only during the breeding season or the non-breeding season but not both (Lima, Casas, Ribeiro, Souza, & Naka, 2018;Motta-Junior & Santos-Filho, 2012;Pawlak, Kwieciński, & Hušek, 2019). Similarly, if only one type (e.g., hawk or owl) or size (e.g., small raptor or large one) of predator (Lima et al, 2018;Pawlak et al, 2019) is presented, then species that mob predators of different types or sizes may also be mis-categorized.…”

“…Thus, studies conducted during a single season risk excluding any species that mob only during the breeding season or the non-breeding season but not both (Lima, Casas, Ribeiro, Souza, & Naka, 2018;Motta-Junior & Santos-Filho, 2012;Pawlak, Kwieciński, & Hušek, 2019). Similarly, if only one type (e.g., hawk or owl) or size (e.g., small raptor or large one) of predator (Lima et al, 2018;Pawlak et al, 2019) is presented, then species that mob predators of different types or sizes may also be mis-categorized. If a predator is a risk for only some species but not others (da Cunha et al, 2017a), then those species at less risk may be classified as non-mobbers, even if they do reliably mob a predator that is more risky for them.…”

Mobbing in animals: a thorough review and proposed future directions

“…Second, while several studies do consider multiple sources of variation, few addressed enough of these possible sources of variation to thoroughly interrogate the entire system. This shortcoming inflates the occurrence of false negatives, for example, the number of species that are classified as non-mobbers when, in fact, the conditions were not ones in which that species mobs (e.g., the type of predator used, time of year, degree of cover Pawlak et al, 2019). As predators are only a risk for some species but not others (Cunha et al, 2017a), this limits a predator's likelihood to elicit a mobbing response from certain species and increases the chance they are classified as non-mobbers.…”