Predefinitive Plumage in the Golden Eagle (Aquila chrysaetos): A Signal of Aggression or Submission? Available to Purchase

In most species of birds, immature plumages are more cryptic than later plumages (Bostwick 2016). Possible explanations suggest that these immature plumages allow more efficient thermoregulation or provide camouflage to avoid predation (Kilner 2006). Alternatively, the submission hypothesis posits that immature plumage can signal lower competitive ability, and thus reduces direct aggression from adults (Montgomerie and Lyon 1986, Muehter et al. 1997, VanderWerf and Freed 2003).

Golden Eagles (Aquila chrysaetos) that are not adults (i.e., aged approximately 0.5 to 4.5 yr old; from their 1^st winter until their 5^th winter) have conspicuous white coloration on the basal half of the tail and white patches on the base of the inner primaries and secondaries (i.e., predefinitive plumage; Bloom and Clark 2001, Liguori 2004, Clark and Pyle 2015). These areas of white are lacking in adults, making...