Re: [SBB] American Dipper in Stevens Creek

[Nancy Teater <[[email protected]]>]

Thanks, Les. After I posted my message about dippers being "early," I 
realized it was a mistake because I knew they didn't migrate. But the 
reports of interdrainage migration make sense for this species. A very cool 
bird.
Nancy

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>
ph 650-949-4335
fx 650-949-4137
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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--
Nancy R. Teater, Hamilton Communications
[[email protected]]
phone 650.321.0252  fax 650.491.3878


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