Display site selection in a ground dwelling bird: the importance of viewshed

Abstract

We studied the effects of visibility, female and male distribution, microhabitat and distance to human infrastructure on display site selection in a ground-dwelling bird, the Canarian houbara bustard. Using a very high-resolution digital elevation model based on LIDAR technology, and a complete census of the breeding population, we compared 98 display sites with randomly generated sites through generalized linear models. Univariate analyses showed that males displayed at locations that increased their visibility, both at short and long distances. Interestingly, although numbers of females and males around sites did not differ between display and random locations, from display locations males could see more females and males at both distance ranges. The absence of vegetation and stones was also critical as it allowed males to perform display runs on a ground free of obstacles. The amount of trophic resources did not correlate with the selection of the display site itself, though an appropriate vegetation cover seemed to be important at a wider habitat scale. Finally, display sites were farther away than random sites from sources of human disturbance, such as urban nuclei, buildings and tracks. Logistic regression analyses confirmed the importance of viewshed, low stone and vegetation cover, and distance to urban centres and tracks, and model averaging identified short-range visibility and females visible in the long range as the most important visibility variables. These results are compatible with the sexual advertisement and predator avoidance hypotheses. We provide recommendations to ensure an appropriate management of the breeding habitat of this endangered subspecies.

Significant decline of an endemic bustard in the Canary Islands

“…As in numerous previous studies (Pettorelli et al 2006;Wiegand, 2008 Interestingly, previous studies also show that although male territories generally include enough vegetation where males can feed or hide, the amount of food resources is not greater at display sites than elsewhere in the vicinity (Abril-Colón et al 2022b; Ucero et al 2023). Moreover, food abundance may critically affect the breeding success of females, who must raise their chicks in places with su cient food.…”

“…Moreover, food abundance may critically affect the breeding success of females, who must raise their chicks in places with su cient food. Males of this species aggregate on exploded leks (Collins 1984;Hellmich 2003;Hingrat et al 2004Hingrat et al , 2008; Hingrat and Saint Jalme 2005), and sites with more abundant resources could serve to attract females (Ucero et al 2023). This would explain why display sites that have remained occupied show both, higher NDVI and higher density of houbaras than sites that have been abandoned.…”

“…Likewise, when repeated locations were available from both current censuses (2020 and 2021), we used data from 2021, when more males were seen displaying. Repeated use of the same display site, both within and between consecutive years, was also con rmed by GPS-tagged males (Alonso et al 2022a; Ucero et al 2023). We used the accelerometer sequences of a sample of display runs identi ed and veri ed in the eld through eld observations of some focal males during the 2020 breeding season to train the AcceleRater software (Resheff et al 2014), and later obtained display runs automatically for the 2021 breeding season (Abril-Colón et al 2023).…”

“…In addition, males select display sites with high visibility from where they can see and be seen by females and competing males (Ucero et al 2023), as described for Great bustard in the Iberian Peninsula (Alonso et al 2012). Therefore, males are more visible than females and so the occupation of display sites year after year can be relatively easily con rmed and has been used as a useful method to census houbara populations (Hellmich 1998;Alonso et al 2022a;Ucero et al 2023). In this study we used the number of males to assess the demographic trend over the last decades.…”

Anthropogenic mortality threatens the survival of Canarian houbara bustards

“…Between late autumn and early spring, males concentrate at lek areas where they display at specific locations of their territories, to which they generally remain faithful over the whole breeding period and also between years 83 . These sites are characterised by a high visibility and low stone and vegetation cover, and are far from human infrastructure 109 . Females visit displaying males for mating and later take over all breeding duties 110 .…”