GROWTH AND PLUMAGE DEVELOPMENT OF NESTLING LONG-EARED OWLS

• Published in: The Condor (Los Angeles, Calif.) Calif.), 2006-11, Vol.108 (4), p.981-985
• Main Authors: Seidensticker, Mathew T, Flockhart, D. T Tyler, Holt, Denver W, Gray, Kathy
• Format: Article
• Language: English
• Subjects: Animal nesting; Asio otus; Bird nesting; Birds of prey; Chicks; concealment; Developmental stages; down development; Eggs; Feathers; Growth and development; growth rate; Hatching; logistic growth function; Ornithology; Owls; Physical growth; Plumage; postnatal growth; prefledging period; Short Communication; Short Communications
• ISSN: 0010-5422; 1938-5129; 2732-4621
• DOI: 10.1650/0010-5422(2006)108[981:GAPDON]2.0.CO;2

We report the growth rates and plumage development of Long-eared Owls (Asio otus) in two developmental stages from hatching to fledging, the nestling period (1–22 days) and prefledging period (23–37 days). We used the logistic growth equation to model nestling mass gain. Mass gain was most rapid during the nestling period. Average mass gain per day was highest between seven and 13 days of age. At 16 days of age nestlings displayed defined facial disks and complete second down. Nestlings left the nest at 22 days of age. Mass gain slowed considerably after nest departure and continued to slow up to fledging. Appearance of defensive and concealment behaviors occurred nearly simultaneously with departure from the nest. To our knowledge this is the first detailed report of nestling growth rates and plumage development for Long-eared Owls in North America.