Re: [SBB] Black Skimmers

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

Disclaimer: I'm just guessing
Theory: We have a sink population because our weather continues to be mild 
and the birds wander up from the south. No really cold days yet this 
winter, for example. Chick mortality suggests something in our environment 
doesn't support breeding success.
Whatever the reason, seeing skimmers is delightful.
Nancy
-------------------------
At 09:31 PM 12/30/2005 -0800, Bill Bousman wrote:
>Folks:
>
>This is a great question.  Is the San Francisco Bay breeding population a 
>source or sink population (or is it too early to tell)?  That is, are the 
>birds nesting here sustaining the population (a source) or are the small 
>increases that we see all from recruitment from the southern populations 
>(therefore, the S. F. Bay area would be a sink).  There are two bits of 
>evidence that I've seen.  Locally, we have noticed fairly high chick 
>mortality.  Skimmers often produce three eggs and often only one chick 
>survives to fledgling.  But there have been a number of local observations 
>of fledged young dying shortly after they've left their nest island.  As 
>many breeding spots are not surveyed regularly, it is difficult to say how 
>regular the pattern is.  Secondly, we have seen banded adult parents in 
>recent years and these have been from southern California, which suggests 
>that southern birds are still moving north and augmenting our breeding stock.
>
>It is interesting to note in the case of a distantly related larid 
>invader, the California Gull, that Shuford and Ryan have concluded that 
>even after 25 years of nesting in the South Bay and a population of more 
>than 25,000 birds, the increase we have seen is largely due to 
>recruitment, that is birds moving in from the interior, rather than local 
>production.
>
>Bill
>
>At 08:35 AM 12/29/05, Nancy Teater wrote:
>>Having seen a couple of reports of 25+ groups of Black Skimmers, does 
>>this mean our area population is growing via local breeding success? 
>>Anyone know?
>>Happy New Year, and good birding,
>>Nancy Teater
>>
>>
>>At 07:50 PM 12/20/2005 -0500, [[email protected]] wrote:
>>> From the Adobe Creek Trail today at 10:20-10:30 a.m., I watched 25-28 
>>> BLACK SKIMMERS just north of "Skimmer Island" in the Charleston Slough, 
>>> across from the pump house and bleachers.  They were not there when I 
>>> walked past the same spot at 9:15 a.m.  This is the first time I have 
>>> seen them back at this location since June.  As I was about to leave, 
>>> Dave Weber came along and counted 28 BLACK SKIMMERS.
>>>Good Birding!
>>>Dotty Calabrese
>>
>>--
>>Nancy R. Teater, Hamilton Communications
>>[[email protected]]
>>phone 650.321.0252  fax 650.491.3878


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