RE: [SBB] American Dipper Temporal Distribution

[Jim Yurchenco <[[email protected]]>]

         Reply to:   RE: [SBB] American Dipper Temporal Distribution
Just to add my two cents to this discussion:  we always have had several AMDI on visits to Smith Creek/Arroyo Hondo on the relatively few trips where we walked substantial portions of the creek downstream from Smith Creek Fire Station, no matter what time of year (and we did all these walks from late spring until just before the first rains).  The lower reaches of this creek have always had significant lengths of flowing water, even in late summer.  However, Coe is a different story. Most of Amy's and my birding time in SCC has been spent at Coe so we are extremely familiar with the place at all times of the year.  At Coe, none of the creeks remain flowing, except in very short localized stretches, during the summer and fall.  As a result, we have almost no AMDI records from Coe and they are certainly not resident there or breeders.  Coe and Smith Creek are just a few dipper air miles apart with some very similar stream-side habitat; the flowing water makes all the difference.

regards

JRY
Bill Bousman wrote:
>[SBB] American Dipper Temporal Distribution
>Folks:
>
> This is an interesting thread--thanks, David, for your valuable comments on
> dipper temporal distribution in Santa Cruz County.
>
> The county notebooks have 25 years of data.  To look at the temporal
> distribution I make plots of sightings per year and sightings per
> week.  Then, with plots in hand, I get out my ouija board and interpret
> what I see.  The plot of sightings per year is a way of looking at
> long-term temporal changes (and observer bias, that is, there are more
> active birders here in 2005 than there were in 1985).  Interestingly,
> although there is a lot of year-to-year variance, there does not seem to be
> any long-term trend in the data, once processed on the ouija board.
>
> The sightings by week plot assumes that I break each month up into a "week"
> of either 7 or 8 days--that way I always get four weeks in a month.  If one
> bird is seen four weeks in a row, then this counts as four
>"sigthings".  Looking at this temporal distribution there is not very much
> variation over the year, although there appears to be a downturn from June
> to early September.  This sort of distribution seems to my ouija board to
> be typical for residents.  That is, we detect a lot of birds in the spring
> and early summer months as they are nesting, but once they are over nesting
> and they are starting their prebasic molt, they tend to become secretive
> and quiet.
>
> There are a number of factors that make it difficult to know the temporal
> status of American Dipper in Santa Clara County with accuracy.  First, most
> of the streams they use in the county are not easily accessible (good for
> dippers, by the way), so it is difficult to census them.  Second, breeding
> pairs tend to be noisy, but when breeding is over, pairs do not share
> territories, so one or both move on.  Three, they are rare.
>
> Some example summer records that may be of interest, from that intrepid
> pair of hikers, Jim Yurchenco and Amy Lauterbach:
>         22 Jul 1984     8, Arroyo Hondo, near Joseph Grant CP
>         25 Aug 1985     7, Smiths Creek, near Joseph Grant CP
> It looks like this drainage, in the 1980s, had substantial numbers, all
> spaced out, of course.
>
> Bill Bousman
> Santa Clara County records compiler
>
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> Subject: [SBB] American Dipper Temporal Distribution
> Date: Thu, 10 Mar 2005 09:23:19 -0800
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