[Tweeters] Numbers of Birds

[Dennis Paulson via Tweeters]

Hello Jim,

The reason the shorebirds aren’t there all year long is because they are mostly migrants, passing through here on their way between breeding areas to the north and wintering areas to the south. Some of them may spend the winter in small numbers, e.g., Greater Yellowlegs and Long-billed Dowitchers, but most are migrants. Short-billed Dowitchers, for example, don’t winter, even though they are quite common in migration, nor do the vast majority of Westerns and Leasts nor species such as Baird’s and Pectoral and Stilt and Short-billed Dowitcher and phalaropes. It would be very interesting to monitor the area all year long to see if any individuals winter there and what happens in the spring. Has anyone observed shorebirds there in spring?

Sticklebacks can be very common. We must have seen a half-dozen caught and swallowed by Greater Yellowlegs while we were there for an hour the other day. There may be hundreds in the channel, so the predation may not take that much of a toll. It’s natural selection, weeding out the ones more likely to be caught. And the invertebrates in the mud that most of the sandpipers (remember, they are all sandpipers except for the Killdeers) eat are there in prodigious numbers. Mudflats are very rich places for burrowing invertebrates. That’s of course why all those shorebirds are there.

Dennis Paulson
Seattle


> On Sep 2, 2024, at 7:29 PM, Jim Betz via Tweeters <tweeters at u.washington.edu> wrote:

> 

> 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

> 

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