本文发表在 rolia.net 枫下论坛Q. How do you tell the whether the bald eagle is a male or female?

A. As with any birds where the genders have non-distinct plumages, the only ways to tell differences in sex are through size dimorphism (i.e., size differences) or in internal examination called a laparoscopy . Bald eagles exhibit size dimorphism; females on the average about 1/3 larger than males. Data compiled by Mark Stalmaster (1987 - "The Bald Eagle" pg. 16) found that 2 size measurements, beak depth and hallux (toe claw) length, show the greatest separation in sexes. These measurements can be used in the following equation: sex = (bill depth x 0.392) + (hallux length x 0.340) -27.694 (measurements in millimeters). If the answer is positive, the eagle is a female. If the answer is negative, the eagle is a male. See if you can figure out the sex of this eagle -- it is 1 of the 4 birds we are tracking in the western study: bill depth = 34.5 mm; hallux length = 43.0 mm.

Practically, I can guess the sex of most birds when they are on the bait and certainly in hand just by general size differences. Birds in the overlap area of the measurements are more uncertain; a subjective way to sex these is by temperament; females are docile and don't bite or squirm...males are very aggressive in hand. I also sex the birds prior to capture by listening to their calls-- the fluting calls of males is almost a scream, females is pitched much lower.更多精彩文章及讨论，请光临枫下论坛 rolia.net