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April 2007

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From:
Bill Whan <[log in to unmask]>
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Bill Whan <[log in to unmask]>
Date:
Thu, 12 Apr 2007 08:53:37 -0400
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        Not everyone on this list will have read this post from yesterday by
Julie Craves. It supplies a larger perspective on our local weather and
its effect on birds. Bob Royse's remarks from the previous day about the
lack of progress of migration even at an early-season hotspot like
Shawnee have a wider context. Insect emergences have been delayed, and
some perhaps wiped out. Here in town the winter's robin hordes have
stripped fruits from nearly everything. Which reminds me to ask if a
local photographer might be interested in helping me get some photos of
what appears to be a daughty Baltimore oriole that's used a feeder to
get through this crazy winter, a rare event; let me know. Anyway, here
are Julie's thoughtful remarks from the Michigan list-serve:

Subject: Reflections on the spring chill of 2007 -- long
From: Julie Craves <jcraves AT umd.umich.edu>
Date: Wed, 11 Apr 2007 13:12:52 -0400

I'm watching the snowflakes begin to fly, again. Lifelong Michigan
residents find this weather and its resultant pause in spring migration
annoying, but somehow 'typical,' although this is actually the longest
stretch of April cold in this region since 1982. This cold spell,
however, has extended all across the eastern United States, and will end
up being far more than inconvenient for migrant birds.  It is likely to
have a profound and long-lasting impact on bird populations.

Already, many insectivorous birds in the south have perished. Last
weekend in south Texas, a birder reported 'over a hundred swallows on
the windows, patio chairs, and palms just outside the door of [a
neighbor's] home.  I counted over 60 by the time I got there and took
photos of 20 or so on one palm branch...2 and 3 deep.  We  identified
barn, cliff, and bank swallows perched on the window sills, patio
chairs, all huddled together.'  These reports continued through
yesterday. The Chimney Swifts and swallows that are not succumbing to
cold and starvation are foraging very low to the ground, especially near
roadways where the pavement generates some warmth and attracts insects.
These birds are being killed in great numbers along highways.

My real concern is for the migrants that have yet to arrive.  Deciduous
trees that were leafed out and/or blooming have been devastated from the
Gulf coast northward. Oaks were in full bloom in the south-central
states, but the blooms are reported now to be brown and crumbling, so
acorn crops in those areas are likely to be nil.  In eastern Kentucky,
this was reported for black oaks. In central Kentucky, a wider variety.
Trees that had produced tender new leaf growth have had these leaves
blackened. In the Knoxville area, hickories, black gums, maples,
redbuds, locusts, and tulip trees are all brown.  Also in Tennessee, one
observer indicates that spring canopy foliage may be reduced 50-80%.  In
South Carolina, Bill Hilton gives a very sobering report (with photos)
of complete leaf kill on all shagbark hickories, hackberries, trumpet
creeper, winged sumacs, and oaks, and heavy freeze damage to walnuts,
mulberries, and above-ground foliage of Virginia creepers, wild grapes,
and poison ivy, among others
(http://www.hiltonpond.org/ThisWeek070401.html).

Beyond what insects were directly killed by freezing weather, the
reduction in leaves will also mean that there will be less foliage
available to insects, and therefore fewer insects available to birds
during migration.  This could have serious consequences for migrants if
they are unable successfully refuel during the journey north. If trees
used up reserves producing the spring flush of leaves, this foliage
reduction may persist throughout the summer; the concomitant reduction
in insects available for nesting birds will surely impact reproductive
success. For tree species in which even woody growth dies back due to a
prolonged freeze, reduced foliage growth or flowering could persist for
the next few years.  It is this reduction in foliage-consuming insects
that has me most concerned.

Birds that manage to make it through the migration and breeding seasons
will not have overcome their final obstacles.  Over much of the eastern
U.S., the fruit crop will be significantly diminished.  I've read
reports from Kentucky and Tennessee that dogwoods, wild plums,
spicebush, blueberries, black cherries, and other early bloomers will
probably set little or no fruit at all this year. In central Kentucky,
holly shoots have been burned back from frost, and may not produce
flowers and berries this year.

I don't mean to sound alarmist. Climate events like this are not
unprecedented in history, of course, and bird populations have had to
deal with them before. But so many species are facing other pressures
that they are not adapted to deal with large-scale habitat loss and
fragmentation in particular that it may be that the spring chill of
2007 could have very long-lasting effects.
Julie A. Craves
Rouge River Bird Observatory
University of Michigan-Dearborn
Dearborn, MI 48128
http://www.rrbo.org"


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