The Odd Colored Primary Drops!

Last night when Ken and I were both away at meetings Alice finally dropped her odd-colored primary!! Now the detective work begins....

My original guess was that this feather was missing pigment because it had been injured as it was growing in. This was based on the fact that Alice was messing around with some itchy new feathers growing in on April 24, 2003, as well as on reading Peter Pyle's "Flight-feather Molt Patterns and Age in North American Owls" which concludes that it may take four or more years for Great Horned Owls to replace all primaries and secondaries.

After digging through bags of Alice's molted feathers, I can now say for sure that this hypothesis was wrong! She molted this feather in 2000 (I didn't record dates at that time), 1 January 2002, 1 June 2003, 26 July 2004, and yesterday, 28 June 2006. So she has molted this particular primary TWICE since the blood episode.

So where does that leave things? A mess!! I think I could do a whole study based on this. Uff da!

Apparently Alice is replacing this feather NEARLY every year, but not EVERY year. The 2002 date was likely so early because at that time we brought Alice downstairs to hang out with us in the evenings, exposing her to much more light than she would normally get in the winter. Other molt dates look more normal (June/July) since we no longer bring her downstairs in the evening but allow her to stay upstairs with the lights off.

Reading Pyle's write up on Great Horned Owl molt more closely now, a couple of statements really stick out. He mentions that Weller's concluded in his 1965 study of captive, known-age birds that "more questions concerning molting patterns were raised than were answered." Streseman and Streseman in 1966 suggested that ALL flight feathers were replaced every year. In talking to Kay McKeever of The Owl Foundation, she also says that her captive owls molt all flight feathers each year. But still Pyle concludes that based on his examination of specimens that Great Horned Owls can be reliably aged for their first few years based on the pattern of flight feather molt since not all are replaced every year.

Sometimes not having any preconceived notions is a very good thing. Laying the feathers out this morning, my husband noticed that the bars on the now-blank part of the vane were getting slightly shorter with each molt until this molt, where they were essentially dropped. This certainly appears to be the case if you look closely, although this last molt was quite a jump. (The feathers are arranged from the current feather on the left to the oldest feather on the right.)

Now I'm curious to see if other feathers are losing pigment over the years. White feathers can be a sign of age, but Alice is only nine as is capable of reaching 30-50 years of age in captivity. And it will be especially interesting to see what Alice's replacement feather looks like.

I can track Alice's tail molt quite easily, since she drops all tail feathers every year, and each is distinct enough from the next. But heck if I can manage to figure out which wing feather is which other than a few outer primaries (this one included). Bob Nero (Great Gray Owls) and Eric Forsman (Spotted Owls) both traced molts in owls by using spread wings of prepared specimens to compare feathers. I have yet to be able to do this even though the Houston Nature Center has several spread-wing mounts of Great Horned Owls. My problem is that Alice is MONSTROUS compared to all other Great Horned Owls around here, and no specimens I have even begin to compare to the size of her feathers.

So if anyone up in Canada ever runs across a nice, big, dead Great Horned Owl with an unflattened wing chord measurement in the 385mm range, I would jump at the chance to apply for permits to get it to the U.S. so I can do some proper comparisons!!