Raptor urbanites
Fri, 9 Apr 2004 08:31:25
-0700
From: Debbie Viess
I think that it's great that the accipiters have adapted so well to our urban landscapes. I sometimes have a Cooper's Hawk perch in my backyard fig tree, hoping for "escapes" from my aviary (I read a study once that said a major part of urban hawk pellets was comprised of cage bird bones) and one time I observed a juvenile Cooper's Hawk jump up and down on top of the aviary in frustration, that he couldn't tear thru the wire and eat my birds. He was so worked up, he wouldn't even flush when I went out there to shoo him away! The adults aren't quite so foolish. When I sunbathe in my backyard, the Cooper's Hawk will fly overhead, below my roof line. It's so nice when the birds come to you! Of course, it helps to live in a "birdie" neighborhood.
Debbie Viess
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Re: Early spring arrival records
Fri, 09 Apr
2004 09:35:38 -0700
From: Travis Hails
Global warming may be happening, but I don't think we can state it is a fact. It a hypothesis based on short-term weather records and climate models. It is true that the climate models do predict recent trends in climate. However, these models have somewhat arbitrary parameters have been "tweaked" to make the models conform with recorded history. After all, I could build a model showing that the probability of dying increases with the number of hamburgers eaten. We all know that most people who die have eaten a hamburger. If I add a factor that excludes people under 2 years of age, my model becomes more accurate. But is it reasonable to do this. Of course, people 80 years have eaten more hamburgers than those only 10, so it is all reasonable and logical, and my model "proves" it.
I know that the last 12 years have 9 of the warmest years on record. And if I remember correctly, the years shortly after the Mayflower had some of the coldest, with snow in August and crop failure. We may be in a short time period between ice ages, as some scientists suggest.
Only time will tell whether global warming is true. To quote from one source does not make it a fact. Science is interpretations of data, and review by others, thereby moving toward a generally accepted theory. Until it can be replicated, it can never become a fact.
In contrast to Orion, please see the review of The Discovery of Global Warming by Spencer R. Weart, reviewed in the American Museum of Natural History magazine Natural History, April 2004.
Until we know more, I will be amazed by birds who winter close to the equator to "predict" the weather in North America and arrive early. What clues in the tropics allow these birds to do that?
Travis Hails
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Re: Early spring arrival records
Fri, 9 Apr
2004 10:06:06 -0700
From: Debbie Viess
Point taken. We may not know what is causing the warming trend, but a warming cycle is apparently in effect, and as has been predicted, it shows up earliest and most strongly at the poles. The Blue Grosbeak is perhaps not the best example of changes in distribution, and certainly not due to arctic conditions, but it does seem to be an indicator of rapid changes afoot. Who knows what cues the birds are really using? I don't. I promise to read the Natural History article if you'll read the one in Orion. Perhaps we'll both learn something.
Debbie Viess
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Re: Early spring arrival records
Fri, 09 Apr
2004 11:07:14 -0700
From: Joseph Morlan
Travis Hails wrote:
Until we know more, I will be amazed by birds who winter close to the equator to "predict" the weather in North America and arrive early. What clues in the tropics allow these birds to do that?
I have heard that there apparently are some, as yet unpublished studies in the East and Midwest suggesting that some species of neotropical migrants are arriving earlier. Such studies need to be based on systematic monitoring of breeding areas on a daily basis over a long period of time. Otherwise it's easy to fall victim to the "birds arrive on the weekend" syndrome. Nevertheless this work remains unpublished and will undoubtedly remain somewhat controversial.
In contrast, there is apparently no evidence that neotropical migrants are arriving significantly earlier or later on the Gulf Coast. I believe that there is good evidence that migratory restlessness in these species is triggered by changes in the length of daylight. This should not change with global warming.
However when one looks at arctic breeding species, there does seem to be abundant evidence of a warming trend. E.g. a long-term study on Black Guillemots in northern Alaska found the ice melting much earlier and the birds arriving correspondingly earlier in recent years.
Joseph Morlan, Pacifica, CA 94044
California Birding & new rarities
http://fog.ccsf.edu/~jmorlan/
California Bird Records Committee http://www.wfo-cbrc.org/cbrc/
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Re: Early spring arrival records
Fri, 9 Apr
2004 16:08:50 -0700 (GMT-07:00)
From: Rich Cimino
I have also been reading about these studies attempting to record new timelines for neotropical migrants arrivals. These are interesting studies. Some baseline thoughts for the potential of early Black-headed Grosbeak and Blue Grosbeak arrival. Using the Blue Grosbeak I heard calling April 3rd and the bird Debbie Voss saw April 6th. Consider this: March 20 was the spring vernal equinox and a new moon ~ making night and day equal in length in the northern hemisphere. This vernal action pulls the sun across the equator going north (in 60 days it will be 20 hour day light in Nome Alaska = very good birding). Have you all noticed the strength of the new full moon beginning on April 5th? Wow, this moon may be a good indicator that we could have "an early spring migration" will this be the norm? This is where I agree with Joe. Studies need to documented via a systematic monitoring procedure over a very long time frame. This is where the record keepers need to have an open mind. Consider all the findings of Bob Richmond along the Hayward shore line, plus countless other which specialize in special areas of individual concern and fun.
Having said that. May I add that boy it sure is fun finding all those "birds that arrive on the weekend." Joe, thanks for all your support and energies that you give birding in Northern California!
Rich Cimino
Pleasanton
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Solitary Sandpiper in Tilden Nature Area, Berkeley
Hills
Fri, 9 Apr 2004 19:43:51 -0700
From: Ken Burton
This afternoon Kay Loughman and I found a Solitary Sandpiper at Jewel Lake in Tilden Regional Park Nature Area (Berkeley Hills). It appeared to be in prealternate molt and remained on a snag in the middle of the lake - not surprising as the shoreline was crawling with humanity.
Ken Burton
Mill Valley