Date:         Fri, 31 Jan 2003 23:28:13 -0500
Reply-To:     Maryland Birds & Birding <MDOSPREY@HOME.EASE.LSOFT.COM>
Sender:       Maryland Birds & Birding <MDOSPREY@HOME.EASE.LSOFT.COM>
From:         Bill Ellis <billellis@ELLISLIST.COM>
Subject:      Comments on the Turkey Point Hawk Watch 2002 Results
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After seeing the counts for the Turkey Point Hawk Watch, provided by
Leslie Fisher in her MDOsprey posting of 12/28/02, a lot of questions
popped into my head.

1.  Is the decline in number because of the decrease in count hours?
2.  Did other hawk watches experience similar declines?
3.  How do the proportions of the individual species with large counts
compare with the nearby hawk watches at Hawk Mountain and Cape May?
4.  How do the proportions of counts of the hawk types (accipiters,
buteos, falcons, etc.) compare with other hawk watches?
5.  Based on the answers to #3 and #4, is the Turkey Point Hawk Watch
like nearby hawk watches, or unique?

I did some calculations to try to answer my own questions.  (An Excel
spreadsheet of these calculations is available directly from me by e-mail.)

My proposed answers, with commentary provided by Leslie, the
Count Coordinator, follow:

        1.  The decline in number is partly because of the decrease in count
hours, since the counts are not normalized for hours spent counting.  The
decrease in hours was about 10 percent, while the decrease in total hawks
counted was about 24 percent.  If the count for 2002 is corrected for the
decrease in hours counting, the decrease reduces to just 15 percent.  (See
the "01-02 Changes" page of the spreadsheet.)

Leslie noted that part of the decreased count hours was weather related,
such as rain days, and other count sites probably experienced this as well.
In general, it was a very wet fall, as well as poor weather patterns in
general for migration.

Parke John, an experienced observer at Turkey Point, also suggested that
the high proportion of novice counters at Turkey Point may cause a low bias
in the counts.

2.  Hawk Mountain did experience a decline from 2001 to 2002 in the total of
the 4 hawks reported to have significant declines at Turkey Point (SS,
RT, RS, AK).  Turkey Point's decline in the total count for the four hawks
was about 26 percent, while Hawk Mountain's decline was 21 percent.  For all
hawks, Hawk Mountain showed an increase, however, of 38 percent, while
Turkey Point's totals dropped as decribed in #1.

Leslie thought it was interesting that Hawk Mountain showed an overall
increase of 38%; perhaps weather patterns influenced the number of birds
choosing a mountain ridge flight path as opposed to a peninsular site such
as Turkey Point.

3.  The proportion of SS at Turkey Point and Cape May (for 2001; 2002 data
were not found) are similar: about 46 percent and 45 percent.  The
proportion of RT at Turkey Point and Hawk Mountain (for 2002) are similar:
about 17 percent and 16 percent.  (See the "Proportions" page.)  Turkey
Point seems to differ a lot from both of the other hawk watches in
proportion of TV.  I suspect that this may be a counting artifact, because
of the difficulty in differentiating migrants from locals at Turkey Point.

Leslie suspected that the latter might be correct.  She also thought it
interesting that Cape May has such a similar percent of SS. A high percent
of Turkey Point SS are immature birds.

Parke John agrees with Leslie about the TV numbers, and suggests further
that the BE numbers are also questionable for similar reasons and Turkey
Point's proximity to Conowingo.

4.  The proportions of hawk types are shown in the Proportions page.
Turkey Point resembles Cape May only for accipiters, and resembles Hawk
Mountain only in having a high proportion of buteos.  Buteos dominate the
count at Hawk Mountain because of huge BW counts; buteos are the second
largest group at Turkey Point, but because of large RT counts.

Leslie agreed that Turkey Point's negligible BW counts do put it way behind
other counts on buteos in general.

5.  Turkey Point is unique among the three counts, with few similarities in
count proportions.  I like that.  And Cheers! to Leslie - your effort and your
counting team's efforts are very worthwhile!

Bill Ellis
Eldersburg, Carroll County

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