Re: [SBB] American Dipper in Stevens Creek

[Les Chibana <[[email protected]]>]

David's comment nudged me to pull out a copy of the Birds of North 
America account for the dipper, and it's good that I did. I had it 
backwards, in the dipper's range, where it freezes in winter, they move 
downstream. Of course, that shouldn't apply here.

The author, Hugh E. Kingery, says that there are 3 types of migratory 
behavior: nonmigratory, in-stream, and interdrainage. So, they either 
stay put, move within the same stream, or move between streams. I 
recall that in one major study in the Colorado Front Range they 
detected a dipper flying outside of its drainage only once. Kingery 
notes that there are only a few documented interdrainage flight 
movements and suggests that these generally occur at night. It seems 
that this is one of those species that are difficult to track for 
migrational data. It does not appear that there is much data if any 
from banding efforts to indicate movements outside of home drainages.

Among the dipper locations within the county, Stevens Creek seems to 
maintain a reasonable flow year-round, undoubtedly being augmented by 
outflow from springs. Doesn't Twin Creeks, upstream from Almaden Res., 
flow year-round? And Penitencia Creek in Alum Rock Park is perhaps a 
bit more intermittent.

I don't doubt that David has a good grasp of presence of most species 
in the areas he frequents. And as he asks, where do they go? 
Apparently, someplace that we don't check...

Les
---
Les Chibana
BirdNUTZ(tm) - Ornigasmic Birding
Palo Alto Baylands Birding Classes
em <[[email protected]]>
web <http://www.birdnutz.com>
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snailmail: SR2 Box 335, La Honda CA 94020


On Mar 8, 2005, at 8:48 PM, [[email protected]] wrote:

> In a message dated 3/3/05 4:14:04 PM Pacific Standard Time, 
> [[email protected]] writes:
>
>
> They may be
>  difficult to locate in winter because they are believed to move higher
>  into their drainage in winter. Or, maybe they aren't looked for much 
> in
>  winter and are under-reported.
>
>
>
>  FWIW, I believe that a significant portion of the dippers that nest 
> or are reared in the Santa Cruz Mountains go elsewhere by late summer. 
> Some are apparently year-round residents, but my take on the 
> population as a whole is that many depart from some streams entirely 
> or from large parts of streams when stream flow conditions deteriorate 
> by sometime in the summer. There are very few of our local streams 
> that provide suitable dipper habitat in late summer and early fall. 
> Without trying to lay out the case for this opinion, I'll just say it 
> is based on observations on a number of the local dipper streams at 
> various seasons, and especially during a transition period that spans 
> the nesting season into summer. But if I'm right that some depart, I 
> wonder where they go?
>
>  David Suddjian
>  Capitola, CA
>  [[email protected]]
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