I've paddled the Arboretum frequently enough the past month to say
with confidence that there have been no Pied-Billed Grebe chicks in
the areas where I saw four nests. So the failure would be a failure
to hatch, not a failure for chicks to thrive. By the way, I still see
about the same number of adults PBGR's in the area, and assume
they're the same pairs that were nesting earlier.

I don't know if the floating nests have the ability to rise with
water levels., nor do I know if the water levels have gone up
appreciably. I do know that I've been unable to find the three nests
that were there a month ago, so a rising water level might account
for that. Anybody know where to research Lake Washington's water
levels over the past two months or so? I found data on levels at the
locks for June, and variation was about four inches. Couldn't find
data for earlier months.

On Sunday, I found a newer PBGR nest with four eggs and will try to
monitor it. Unfortunately, it's considerably more exposed to canoe
traffic than the nests that are now missing.

One thing I wonder about is predators. Nutria are said to be strict
vegetarians (can anyone confirm this?). Muskrats are primarily
herbivores but occasionally carnivorous. I imagine Great Blue Herons
and crows could be a big problem for the grebes. Predation would not
account for the disappearance of existing nests, however.

Marc Hoffman
Kirkland, WA
http://www.dartfrogmedia.com
mailto: tweeters at dartfrogmedia dot com


At 07:21 AM 7/1/2008, you wrote:
>I've visited sewage treatment plants in the U.S. and Mexico. The
>birds are drawn to them! I doubt that human fecal contamination
>threatens birds as much as accumulated bird droppings on platform
>feeders, which can incubate Salmonella, etc. However, human sewage
>is laced with household chemicals and other bad stuff routinely
>flushed down the drain, and that is bad for all living things. The
>major sources of harmful pollutants are stormwater runoff from our
>highways and industrial chemicals that concentrate in food stocks
>(fish) and make their way up the food chain.
>Gene Bullock
>Poulsbo
> ----- Original Message ----- From: <notcalm at comcast.net>
>To: "Tina Blade" <tinablade at comcast.net>; "'Tweeters'"
><tweeters at u.washington.edu>
>Sent: Monday, June 30, 2008 11:23 PM
>Subject: Re: [Tweeters] Fate of nesting pied-billed grebes in the Arboretum
>
>
>>Hello,
>>
>>Was there any study of nesting birds during and following the sewage spill?
>>Some of the marshes and ponds at Montlake (UBNA) were posted as
>>contaminated for a period of time. Are very young birds vulnerable
>>to this type of pollution?
>>
>>Dan Reiff
>>Mercer Island
>>
>>
>>-------------- Original message ----------------------
>>From: "Tina Blade" <tinablade at comcast.net>
>>>Hi Tweets,
>>>I'm wondering whether any of you can explain what's happened to the many
>>>Pied-Billed Grebes who were nesting in the Arboretum this spring.
>>>
>>>About a month or so ago, I saw many of them nesting there, and eagerly
>>>awaited the arrival of their babies. I've gone back several times since, and
>>>have not seen any Pied-Billed mamas with babies either in tow or on their
>>>backs.
>>>
>>>I'm wondering if they couldn't handle the stress of the human traffic in the
>>>area.
>>>
>>>Thanks,
>>>
>>>Tina Blade
>>>Kirkland, WA
>>>mailto:tinablade at comcast.net