Defending as a unit: sex- and context-specific territorial defence in a duetting bird

Abstract

Behaviours such as territorial defence represent functionally integrated traits that underlie multiple behavioural variables such as physical and acoustic responses. Characterizing the multivariate structure of such traits is fundamental to understand their evolution. In bird species that form stable pair bonds and are territorial year-round, both sexes are expected to defend their territory; however, the role that each sex plays in defending their shared territory remains largely unknown. Evidence for the sex-roles during territorial defence is mixed and sex-and context-specific characterizations of territorial defence embracing the multivariate nature of the trait are currently lacking. Here we investigated sex-and context-specific variation in a hypothesised latent variable called "territorial defence" and tested whether duets were part of territorial defence in a wild population of rufous hornero (Furnarius rufus). To do so, we combined a simulated territorial intrusion approach during nest building and provisioning contexts with a structural equation modelling approach. Our results showed that, in males and females, the six measured behavioural variables were linked by a single latent trait, territorial defence, in both contexts. Flights over the decoy and duet songs were equally good proxies of territorial defence. Although males were defending more the territory than females, pair members showed a positive correlation in their behaviour. The structural equation modelling framework enabled us to capture a complex correlation pattern among behavioural variables, expanding upon a classic body of research on territorial defence. Thus, the combination of classical behavioural approaches with sophisticated statistical analyses brings new exciting possibilities to the field of behavioural ecology.

Conspecific density and habitat quality drive the defence and vocal behaviour of a territorial passerine

“…We measured three variables related to bird movement and presence (Bollen 2003, Mentesana et al . 2020): response (yes/no); latency or time to test response (seen or heard), defined as the time elapsed (in seconds) since the test started until the male appeared; and minimum distance (in metres) of approach to the sampling station (Table 2). In addition, we measured five variables related to the acoustic response of males to the playback: vocal activity rate, singing rate, calling rate, alarm rate and clucking rate (Table 2).…”

“…Behavioural variablesEight variables were considered characteristic of the territory defence behaviour of male Dupont's Larks. We measured three variables related to bird movement and presence(Bollen 2003, Mentesana et al 2020): response (yes/no); latency or time to test response (seen or heard), defined as the time…”

The causes and implications of sex role diversity in shorebird breeding systems

“…The social environment may also influence display patterns (Pitelka et al 1974). Territoriality and territorial displays often form a key component of bird reproduction before and after pair-formation as a result of their association with better access to food, nesting sites or mates (Brown 1969, Mentesana et al 2020. As local competition for mates and resources may increase with the number of conspecifics, variation in local densities is likely to drive differences in territoriality between populations and species.…”

Nuthatch (Sitta europaea) responses towards simulated territorial intrusion (STI) vary in strength during the non-breeding season — a matter of temperature and photoperiod?

“…Most research has focused on territorial behaviour of males during the breeding season in temperate zones and northern latitudes (Barnett et al, 2014;Billerman & Carling, 2016;Byers, 2017). Studies in year-round territorial aggression (both during and outside the breeding season in both sexes) have been conducted mostly in tropical birds (Greenberg & Gradwohl, 1983;Stutchbury & Morton, 2001;Fedy & Stutchbury, 2005;Dowling & Webster, 2016;Odom et al, 2017), but also in the temperate zones of the southern hemisphere (Fraga, 1980;Ippi et al, 2017;Mentesana et al, 2020). Interestingly, a growing body of evidence indicates that some species exhibit year-round territoriality in northern latitudes (Wingfield, 1994;Goymann & Landys, 2011;Landys et al, 2013;Randler & Randler, 2020).…”