RE: [SBB] Western Tanager & Spotted Sandpipers

["Alvaro Jaramillo" <[[email protected]]>]

Birders

  Spotted Sandpipers have very different breeding behaviour than most birds,
and they are much more like Phalaropes than anything else most birders are
familiar with. Spotted Sandpipers are sex role reversed, so the females are
larger and "compete" with each other for access to breeding males. The males
do all of the parental care, and females are known to have more than one
male mate (polyandry). Therefore once a female mates and lays a clutch she
moves on to another male, if available, and repeats the process. Thus, how
you define a pair is actually very complicated. 

Note that sex role reversed is the standard term in behavioural ecology to
refer to situations where males are the limiting sex in calculations of
reproductive success, a scenario that selects for inter-female competition
and usually larger size and ornamentation. It implies that this situation is
somehow incorrect (reversed) but really this just refers to the reality of
this breeding system being rarer than the one we are used to. Sex-role
reversal is moderately common in various shorebirds and other birds, and it
is also known in many amphibians and fish - mammals have about the most
conservative family values in the animal world, kind of boring in the wide
spectrum of behaviour. 

Cheers

Al

Alvaro Jaramillo
[[email protected]]
Half Moon Bay, CA

Field Guides - Birding Tours Worldwide
http://www.fieldguides.com/home.htm


> -----Original Message-----
> From: south-bay-birds-bounces+chucao=[[email protected]]
> [mailto:south-bay-birds-bounces+chucao=[[email protected]]] On
> Behalf Of Bill Bousman
> Sent: Wednesday, April 27, 2005 5:22 PM
> To: [[email protected]]; South-Bay-Birds
> Subject: Re: [SBB] Western Tanager & Spotted Sandpipers
> 
> Dear Randy and everyone,
> 
> At 12:24 PM 4/27/05, [[email protected]] wrote:
> >Hi Everyone,
> >
> >Another recent sighting has given rise to a question.  Yesterday,
> Tuesday,
> >I was birding along San Fransquito Creek at the end of Geng Rd in Palo
> >Alto.  I saw two Spotted Sandpipers foraging together.  Usually seen as
> >single individuals in the Bay Area, I was wondering if there have ever
> >been any evidence of breeding in or around the South Bay?  I think of
> them
> >breeding being more in the Sierras.
> 
> They nested along the Russian River at the end of the 19th century, but
> nesting further south appears more recent, at least if you look only at
> first nesting records.  In Santa Clara County our first record was in 1989
> and we found them nesting in scattered locations in four blocks during the
> atlas period of 1987 to 1993.  All nest locations have been in low-
> gradient
> streams on the valley floor.  Last year they nested at Almaden Lake.
> 
> We have irregularly had birds along the Bay edge in summer and we have
> discussed the possibility of breeding in some area with gravel, somewhat
> like the low-gradient stream beds they use now.  But our conclusion is
> that
> these are nonbreeding birds.
> 
> 
> >The next question would be, do they pair up prior to moving to breeding
> areas?
> 
> Good question.  Another question is how does one define a pair.  Breeding
> pairs in the county have been very active with lots of calling to each
> other and flight displays, jumping in the air, etc.  Really quite
> spectacular.  Two birds without courtship behavior may be just two
> migrants
> or nonbreeders.
> 
> Bill Bousman
> Santa Clara County records compiler
> 
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