ADAPTIVE SIGNIFICANCE OF GROWTH-PATTERNS IN JUVENILE SPOTTED OWLS

We examined relative growth patterns of six morphological features of fledgling spotted owls (Strix occidentalis). Juvenile spotted owls exh ibit early nest desertion, possibly to avoid parasitism or detection b y predators or to reduce thermal stress. Because juveniles leave the n est before they are capable fliers, they primarily use morphological f eatures other than their wings and tail to move among roost locations. When juveniles fledged, mass, wing chord, and tail length were still increasing, whereas tarsus length and bill depth were near adult size. Moreover, juvenile bill length was greater than mean adult bill lengt h for nearly all time periods. Early growth in tarsi and bills may inc rease juveniles' ability to effectively locomote after they have fledg ed but before they can adequately fly.