CONICET | Buscador de Institutos y Recursos Humanos

Numerous owl species exhibit small feathers on the head that resemble horns or ear tufts that are visible when individuals are resting. This plumage feature is mainly observed in species of the genus Bubo and Otus, but also occurs in other genera such as Asio, Ptilopsis, Ketupa, and Lophostrix (Duncan 2003, Owls of the world: their lives, behavior and survival. Firefly Books, New York, NY U.S.A.). Other owl species, however, have inconspicuous ear tufts that are not visible even when birds are captured and handled. Under stressful situations, these species erect lateral, post-ocular crown feathers up to a height that does not exceed the top of the head plane. These feathers are similar in length to the remaining head feathers and are erected in a continuous motion when birds change their body shape from rounded to oblong (Holt and Peterson 2000, in A. Poole and F. Gill [EDS.], The birds of North America, No. 494, The Academy of Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. survival. Firefly Books, New York, NY U.S.A.). Other owl species, however, have inconspicuous ear tufts that are not visible even when birds are captured and handled. Under stressful situations, these species erect lateral, post-ocular crown feathers up to a height that does not exceed the top of the head plane. These feathers are similar in length to the remaining head feathers and are erected in a continuous motion when birds change their body shape from rounded to oblong (Holt and Peterson 2000, in A. Poole and F. Gill [EDS.], The birds of North America, No. 494, The Academy of Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. survival. Firefly Books, New York, NY U.S.A.). Other owl species, however, have inconspicuous ear tufts that are not visible even when birds are captured and handled. Under stressful situations, these species erect lateral, post-ocular crown feathers up to a height that does not exceed the top of the head plane. These feathers are similar in length to the remaining head feathers and are erected in a continuous motion when birds change their body shape from rounded to oblong (Holt and Peterson 2000, in A. Poole and F. Gill [EDS.], The birds of North America, No. 494, The Academy of Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. survival. Firefly Books, New York, NY U.S.A.). Other owl species, however, have inconspicuous ear tufts that are not visible even when birds are captured and handled. Under stressful situations, these species erect lateral, post-ocular crown feathers up to a height that does not exceed the top of the head plane. These feathers are similar in length to the remaining head feathers and are erected in a continuous motion when birds change their body shape from rounded to oblong (Holt and Peterson 2000, in A. Poole and F. Gill [EDS.], The birds of North America, No. 494, The Academy of Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. in other genera such as Asio, Ptilopsis, Ketupa, and Lophostrix (Duncan 2003, Owls of the world: their lives, behavior and survival. Firefly Books, New York, NY U.S.A.). Other owl species, however, have inconspicuous ear tufts that are not visible even when birds are captured and handled. Under stressful situations, these species erect lateral, post-ocular crown feathers up to a height that does not exceed the top of the head plane. These feathers are similar in length to the remaining head feathers and are erected in a continuous motion when birds change their body shape from rounded to oblong (Holt and Peterson 2000, in A. Poole and F. Gill [EDS.], The birds of North America, No. 494, The Academy of Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. survival. Firefly Books, New York, NY U.S.A.). Other owl species, however, have inconspicuous ear tufts that are not visible even when birds are captured and handled. Under stressful situations, these species erect lateral, post-ocular crown feathers up to a height that does not exceed the top of the head plane. These feathers are similar in length to the remaining head feathers and are erected in a continuous motion when birds change their body shape from rounded to oblong (Holt and Peterson 2000, in A. Poole and F. Gill [EDS.], The birds of North America, No. 494, The Academy of Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. Natural Sciences, Philadelphia, PA and The American Ornithologists Union, Washington, DC U.S.A.). Although the ecological function of this display is unknown, it has been associated with concealment or camouflage that can disrupt bird coloration, making individuals less conspicuous. Holt and Peterson (2000) observed this reaction in Northern Pygmy-Owls (Glaucidium gnoma) when potential predators were placed before captive owls and in the wild when birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius funereus), and Northern Saw-Whet Owls (Aegolius acadicus; Catling 1972, Auk. birds of prey or flocks of passerines were present. Human presence was reported to produce concealment reactions in both sexes of Boreal Owls (Aegolius fu

enviar mensaje