The territorial behaviour of the enigmatic Dupont's Lark has been studied in detail for the first time, revealing how males react differently towards intruders based on the quality of their territory.
Territorial behaviour is widespread in birds, with many species defending a fixed area that enables access to food, mates and other resources. Active territorial defence, where intruders of the other or sometimes other species are seen off vocally or physically, can reflect the quality of the defending bird or the territory the occupy.
Dupont's Lark, which is found in steppe in Spain and North Africa, is a socially monogamous and globally Vulnerable ground-nesting songbird that breeds between late February and late June. Not only are Dupont's Larks sedentary, but males maintain their territory year-round, ramping up its defence during the breeding season.
Dupont's Larks stay in their territory year round, increasing defensive behaviour during the breeding season (Didier Vieuxtemps).
In a paper published in Ibis, a team led by Adrián Barrero assessed whether individual Dupont's Larks' territorial reponse, to a playback experiment, was related to habitat quality or the density of other individuals in the area. They looked at the body condition of the male birds, to see whether there was any relationship with the intensity of the defence.
Defence intensity was measured by looking at the amount of time it took for each bird to respond to the playback, the distance of the bird from the playback, and various singing performance parameters.
The team found that male Dupont's Larks responded more strongly in areas with higher densities or other males, and that males in higher-quality areas met the playback with higher vocal activity, singing more intensely. However, body condition was not related to the 'passion' behind the territorial response.
In poorer-quality areas, the male larks reacted quickly to the territorial intrusion represented by the playback, but they did so cautiously, often alarm calling without delivering intense bursts of song.
The findings suggest that male Dupont's Larks in better-quality habitat are more fervent defenders of their territory, while individuals in suboptimal areas behave as 'floaters', only tentatively answering back to potential intruders. The team said that future studies should incorporate data on the reproductive status of individual birds to investigate whether there is a link with territorial defence.
Reference
Barrero, A, Gómez‐Catasús, J, Pérez‐Granados, C, Bustillo‐de la Rosa, D, and Traba, J. 2023. Conspecific density and habitat quality drive the defence and vocal behaviour of a territorial passerine. Ibis, DOI: https://doi.org/10.1111/ibi.13295
