[Tweeters] Numbers of Birds

[Jim Betz via Tweeters]

Hi all,

   For the last month or more I've been going to Channel Drive. This is 
a superb habitat for

shorebirds and ducks ... and other birds as well.  There are easily 
several hundred birds

there "every low tide" with perhaps 80% ducks and the rest are 
sandpipers, dowitchers,

yellowlegs, etc.  There are a few gulls every day and several GBH.  The 
most common

raptors are peregrines, harriers, and the occasional eagle. Channel 
Drive is a long

inlet/slough - perhaps a couple of miles or more in length and an 
average of 50 yards

or so wide.  It covers in brackish water every high tide and uncovers 
perhaps 80% or

so of the mud every low.

   My question is "why don't the birds exhaust the food supply?". Even 
if the only

birds consuming the sticklebacks were the shorebirds - that's a lot of 
birds and

working every daylight tide.  It is not uncommon to see a yellowlegs 
catch and

down one of these small fish - and I'm guessing that it is at a rate of 
at least

one every 30 minutes (more is likely).

   Does anyone know the reproductive and growth rates of the small fish 
(such as

sticklebacks)?  What about 'life cycle' questions such as "do the small 
fish stop

reproducing in other seasons?" and the related "why aren't the 
shorebirds here

in large numbers year round?"

          - just trying to understand the inter-related aspects of the 
food and the birds ... Jim