Interpopulation Comparisons of Antipredator Defense Behavior of the Thorn‐Tailed Rayadito (Aphrastura spinicauda)

Abstract

The high impact of predators on breeding success has favored the evolution of diverse behavioral strategies that enhance both individual survivorship and reproductive success. Self‐ and nest‐defense against predators are inter‐related behaviors that vary according to life history traits and the risks involved in defense. In addition, interpopulation differences in the composition of predator guilds, and hence predation pressures, may result in geographic variation in antipredator defense strategies. It is generally accepted that the absence of predators could drive the loss of antipredator behavior. However, it is unclear how species respond if one type of predator (e.g., a specialized nest predator) is absent but others are present. The multipredator hypothesis suggests that the absence of only a few predators is not sufficient to drive a change or loss of antipredator behavior in a species. We examined interpopulation variation in defense behavior in the thorn‐tailed rayadito (Aphrastura spinicauda), a suboscine bird inhabiting a wide latitudinal range in southern South America. In populations where nest predators were either present or absent, we examined the responses of rayaditos to an adult predator (an owl) and to a nest predator (a marsupial). Owl‐defense behavior involved more intense and longer responses than marsupial‐defense. This suggests that adult rayaditos may allocate more energy to defend themselves than their young. However, because the presence of adult predators near the nest also prevents parents from feeding the nestlings, owl‐defense may simultaneously represent a form of nest‐defense. No differences in marsupial‐defense were found among the three sampled populations, despite the absence of native mammalian nest predators in one population. The lack of variation in nest‐defense behavior provides some support for the multipredator hypothesis, although the high interpopulation gene flow in this species could also contribute to this behavior's maintenance.

Differences in measures of boldness even when underlying behavioral syndromes are present in two populations of the song sparrow (Melospiza melodia)

“…These studies suggest song sparrows show a greater mobbing response to a more threatening stimulus, similar to what has been found in studies of other bird species (Templeton et al 2005;Templeton and Greene 2007). Studies in several taxa have found that mobbing responses can be strong in animals even in populations where predators are absent (Ippi et al 2013;Owings and Coss 1977) and that animals can retain fear responses to absent or extinct predators Blumstein and Daniel 2002; Burns-Cusato et al -Jammes et al 2014). In addition, the correlation we observed between aggression and boldness (as measured by response to alarm calls) suggests that variation in response to alarm calls is strongly dependent on the personality of the responding individual-rather than the threat of predators in the habitat.…”

Exploratory behavior, but not aggressiveness, is correlated with breeding dispersal propensity in the highly philopatric thorn‐tailed rayadito

“…We tested each breeding pair three days after exploration experiments when nestlings were 15–16 d old. We placed a stuffed mount of a male rayadito at 3–5 m from the nestbox, and played back tape‐recorded songs of a male (see details in Ippi et al , ) during 10 min. A hidden observer at 10–15 from the nestbox recorded all behaviors on a Sony™ ICD‐BX700 ® digital voice recorder.…”

“…The same mount was used for all birds assayed and all experiments involved the same observer. Recordings were analysed with JWatcher to extract two variables: 1) alarm activity, measured as the total number of movements during the trial (Ippi et al ), and 2) the total number of aggressive interactions with the intruder, including pecking the intruder, flying over the intruder or hovering close to it. There was a moderate, positive correlation between the number of aggressive interactions and alarm activity (Pearson's r = 0.42, p = 0.08, n = 74).…”

Nestling Mortality as a Consequence of Interspecific Competition between Secondary Cavity Nesters in the Sub-Antarctic Forests of Chile

“…During November 2013, as part of a long-term study of the breeding biology of the Thorn-tailed Rayadito (Aphrastura spinicauda) at Isla Navarino (55u 569 S, 67u 399 W; see Ippi et al 2013, Quirici et al 2014, located in the Magallanes and Chilean Antarctic Region, we observed two Chilean Swallows (Tachycineta meyeni) entering an occupied nest box and attacking a 13-day-old nestling rayadito. A pair of breeding rayaditos initially occupied the nest box on 6 October 2013, and five eggs were laid between 10-18 October.…”

“…In both cases, only one swallow entered the box, while the other remained calling in flight nearby. Although breeding rayaditos are usually very aggressive towards any potential threat (see Ippi et al 2011Ippi et al , 2013, both adult rayaditos stayed away from the site during these interactions and emitted infrequent and faint alarm calls. This type of 'submission' behavior has never been reported in similar contexts, and its potential causes are difficult to explain.…”