Inter- and intraspecific competition for food in old world vultures

Associations of Avian Facial Flushing and Skin Colouration with Agonistic Interaction Outcomes

“…1992). Some authors have asserted that birds with flushed heads are dominant (König 1976; Mundy et al. 1992).…”

“…Agonistic interactions between lappet‐faced vultures apparently involve several distinct behaviours and visual characteristics. To initiate an interaction, the vultures adopt a threat posture (König 1976; Mundy et al. 1992) in which they stand upright with wings half‐open and chest feathers erect.…”

The colourful White-headed Vulture Aegypius occipitalis: enhancement of threatening signals for interspecific competition?

“…Although the White-headed Vulture lacks the Lappetfaced Vulture's imposing approach to the vulture crowd, it is quicker to jump in, with its more contrasting colouration displayed (e.g. Figure 6 in König 1976). Its appearance of a very excited Lappet-faced Vulture might work together with its sudden action to frighten busy vultures for the short time needed to secure its food -on the other hand, its conspicuousness would turn to disadvantage in case of longer stays with a piece of food near the griffons, hence the frequently observed attacks from them.…”

“…Given that several vulture species make the same colours more obvious during threatening displays (König 1976), it may be more than a coincidence that the dominant Lappetfaced Vulture is one of the most colourful vultures, with much contrast between white and dark on plumage and the ability to change the skin colour of naked areas into a deeper or paler pinkish red, depending on the degree of excitement. The White-headed Vulture not only shows a clearer-cut colour pattern than the Lappet-faced Vulture on the same parts of the body, but also those colours that depend on the motivational state of the bird are usually more vivid.…”

“…These considerations suggest that some colours are rather general signals for vultures. König (1976) sees the reddening skin and contrastingly white plumage as threatening colours and suggests that they might work not only intra-but also interspecifically. Negro et al (2006) propose the same among the possible functions of flushing colours.…”