The Importance of Visual Cues for Nocturnal Species: Eagle Owl Fledglings Signal with White Mouth Feathers

Abstract

Complex begging display by bird offspring has predominantly been investigated in diurnal species, which have conspicuous gape colours or plumage features. In nocturnal species, in contrast, such visual communication has received little attention because the assumption is that they exclusively rely on vocal communication. Here, we use a field experiment to investigate whether eagle owls, Bubo bubo, communicate through visual signals at night. We artificially decreased the brightness of the white feathers surrounding fledgling eagle owls’ mouths during the post‐fledging dependence period, and investigated the effect of this treatment by comparing the condition of these birds to that of birds who received a control treatment. Several physiological parameters considered in our analyses indicate that control owlets were in better condition than owlets with brightness‐reduced mouth feathers, which suggests that they received more or better food from feeding parents who discriminated between those young. Brightness‐dependent reactions of parent owls suggest that visual signalling may be more widely employed than previously thought, and studying birds at night may reveal sophisticated strategies of animal communication.

Social status influences microhabitat selection: breeder and floater Eagle OwlsBubo bubouse different post sites

“…Such a value was calculated when, after a triangulation, we needed to locate the individual exactly to manipulate it during field experiments (e.g. Penteriani et al. 2007b) or to record the cause of mortality if it died.…”

“…2008c). Breeding owls select precise plucking and defecation sites within their nesting sites (Penteriani & Delgado 2009b,c), territory holders repeatedly use call‐posts during vocal and visual communication (Delgado & Penteriani 2007, Penteriani et al. 2007a,b) and breeders and floaters tend to be faithful to the same diurnal roosting sites when ending their nocturnal activities (Delgado et al.…”

PCR-based detection and genotyping of haematozoa (Protozoa) parasitizing eagle owls, Bubo bubo

“…Although some aspects on the ecology of this host-parasite system have been recently studied (Ortego and Espada 2007;Ortego et al 2007a;Penteriani et al 2007), no information is available on the genetic characteristics of this parasite. On the light of recent evidence for cryptic speciation in several avian blood parasites, leucocytozoids parasitizing eagle owls could be constituted by a complex of genetically differentiated lineages or even different good species that may be confined to a single host species or shared with other Strigiformes (e.g.…”

Do adult eastern bluebird, Sialia sialis, males recognize juvenile-specific traits?

“…Functional explanations regarding the appearance of juvenal plumage have been few (Penteriani et al 2007; Tanner & Richner 2008; Galvan et al 2008), possibly because drab juvenal plumage is presumed to represent an ancestral appearance with no current functional significance (Maley & Winker 2007). …”