tweets,

Well put Dennis.

Amy Schillinger
Renton, WA
schillingera at hotmail.com


From: dennispaulson at comcast.netSubject: Re: [Tweeters] very late migrant?Date: Tue, 17 Jun 2008 10:24:07 -0700To: tweeters at u.washington.eduDianne and Amy et al,

I think Pacific-slope Flycatchers are one of many species that breed in forested environments all around Seattle but probably don't breed in the city any more, except perhaps in our most spacious parks. We badly need continued censuses of birds in the city parks, just to see if I'm right. I'm certainly right about my yard and the well-wooded Thornton Creek ravine behind it, where I have never before detected a PSFL in the summer in 17 years of living here.

The city is losing birds, particularly migrant birds, especially those that migrate to the tropics. These are birds that have to arrive in migration and set up territories anew every spring. It is fairly well known that cities can be POPULATION SINKS, places where populations would decline, because mortality exceeds natality (production of young), if it weren't for continuing immigration from the surrounding natural habitats (which are POPULATION SOURCES). As we develop and expand the suburbs around the city more and more, we are essentially pushing the population sources farther and farther away, to the point at which certain species disappear completely from the city, even though there are appropriate habitats here and there. This really seems to affect migrants more than residents, which can make do with reduced habitat quality. One reason they do, I suppose, is because so many of the resident species are aided and abetted by bird feeders. Not so with Pacific-slope Flycatchers.

In some species, individual male birds continue to come into what seem like acceptable habitats in the city, sing their little hearts out, but fail to attract a female. Perhaps the females are better at assessing the value of habitats. If I were a female, I would certainly try to find the very best breeding habitat when I arrived from a winter in Mexico, and it wouldn't be a 10-acre patch of woodland in a city park surrounded by development.

We also need a lot more research on, for example, the density of insects available to an insect-eating bird in a wooded city park as opposed to a similar forest outside the city. I suspect there will be a substantial difference. Having wooded parks and green belts in a city is a great idea, and a wonderful amenity for both humans and some subset of wildlife, but we are kidding ourselves if we think these habitats will support the same biodiversity as the expanse of natural forest that used to be here.

Dennis



Date: Mon, 16 Jun 2008 10:37:10 -0700
From: Diann MacRae <tvulture at vei.net>
Subject: RE: [Tweeters] very late migrant?
To: amy schillinger <schillingera at hotmail.com>
Cc: Tweeters at u.washington.edu
Message-ID: <6.2.5.6.2.20080616103421.023c3620 at vei.net>
Content-Type: text/plain; charset="us-ascii"

Hi Tweets, Amy, and Dennis

I have lived in a very forested area of Bothell for over twenty
years. I have Pacific-slope flycatchers all summer, every year. They
are pretty vocal. I'm not sure why they would stay all summer and not
nest, especially when it goes on every year.

Cheers, Diann

Diann MacRae
Olympic Vulture Study
22622 - 53rd Avenue S.E.
Bothell, WA 98021
tvulture at vei.net

-----
Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382
dennispaulson at comcast.net

_________________________________________________________________
Need to know now? Get instant answers with Windows Live Messenger.
http://www.windowslive.com/messenger/connect_your_way.html?ocid=TXT_TAGLM_WL_Refresh_messenger_062008