WPBO Owl Research

Saturday, August 25, 2007

Welcome to the WPBO owl research blog! This blog is specifically for research topics that we have written about informally at WPBO. If you are looking for updates on our spring, summer, or fall owl programs, please go to our other blog: www.wpboowls.blogspot.com. The papers that you see here are not to be reproduced or copied in any way, but you may view to your hearts content.

Sexing Long-eared Owls

There is currently no way to sex Long-eareds using measurements. Some individuals may however be sexed by plumage, females have buffier colorations than do males. The two photos below represent the two extremes of plumage among approximately 550 Long-eareds I have seen in hand. In determing sex we consider coloration of the breast, facial disk, and underwing and undertail coverts. Notice also the color of the underside of the flight feathers, including rectrices. These birds were both captured in spring and were sexed solely by plumage, both birds were adults. There are many intermediate birds that we sex as unknown.

Feather wear and sun fade

There is often a high level of sun fade exhibited by Boreal Owls, and to a lesser extent by Saw-whet Owls. This is somewhat suprising in species that we think of as highly nocturnal and spending their days roosting in dense cover. The older the feather is the more significant the level of fade becomes. Among the primaries the effects of fade due to sun exposure is most obvious on the central pp’s, particularly pp 6+5 (figures 1+2). Many individuals show crescent shaped pale areas located on the tips of these feathers, and the contrast is best seen on the spread wing. By then closing the wing it is evident that the fade is occuring on the portion of the feather exposed beyond the tip of the shorter feather to the inside of the faded feather tip, e.g. the fade on P6 ocuurs were it is exposed beyond the tip of P5 when the wing is closed. In fig. 1 all feathers are the same age, in fig. 2 the fade is present on old feathers and the feathers in the upper right are new. The consequence of this to banders is that feathers with faded tips may be mistakingly detemined to be older than feathers of the same age that do not have faded tips. Both of these photos are of Boreal Owls.

Saturday, August 25, 2007

Blog Archive

About Me

Sexing Long-eared Owls

Active flight feather molt

Feather wear and sun fade