Rouge River Bird Observatory
Loon migration at Metro Beach, 1992-97
In 1995, RRBO took over the coordination of an informal spring Common
Loon migration survey that was started at Metro Beach Metropark in Macomb
Co. in 1992. Metro Beach lies along the western shore of Lake St. Clair
beween Lakes Huron and Erie. RRBO standardized the count methods to try
and better understand the migration of Common Loons in the lower Great
Lakes.
Over the 6 years, 4114 loons have been counted. Here is a summary of
our results:
Common Loon migration at Metro Beach, 1992-97
|
Year
|
Count days
|
Total hours
|
Loon per 10 hrs.
|
Total loons
|
|
1992
|
42
|
120.0
|
59.1
|
709
|
|
1993
|
40
|
100.5
|
47.7
|
479
|
|
1994
|
49
|
165.0
|
60.1
|
991
|
|
1995
|
56
|
268.0
|
21.8
|
583
|
|
1996
|
60
|
228.0
|
27.9
|
637
|
|
1997
|
31
|
121.5
|
58.8
|
715
|
Flight direction
Of the 2,952 loons whose flight directions were recorded over the six-year
period, 47% were traveling north, 37% northwest, and 12% northeast. Only
3% of the loons were flying in a direction with no northerly component.
Thus, the Common Loons observed at Metro Beach are clearly migrating.
Dates of passage
Peak flight between 27 April and 2 May: 47.9% of all loons are counted
between these days. Most days during the 25 March to 1 June field season
are dull, with 70% of the days having fewer than 10 loons.
Wind and weather conditions
Loons have an apparent strong preference for flying into head winds. Out
of the 65 days over the five-year period that had 15 or more loons counted,
64.6% of the days had winds with a northerly component. On those days,
83% of the loons were counted on days when winds were blowing from the
north (29.7%), northeast (36.1%), or northwest (17.2%). Weather conditions
were recorded daily beginning in 1995. During the peak migration period
from 27 April to 2 May during 1995-97, only 25% of the days had northerly
winds, yet 92.2% of the loons flew on those days. Thus, even though nearly
half of all loons will migrate during this 6-day window, the vast majority
of them will only fly into a head wind.
Time of passage
Prior to 1995, it appeared that the majority of the loons passed by between
0800 and 1000 EST. This was due primarily to lack of observation time:
from 1992-94, 17.75 hours were logged between 0600 and 0800 hours, and
about 9.5% of the loons were counted during this time. In 1995-96, 250.75
hours were logged in these two hours, and over 65% of the loons were seen
in this time period, a dramatic change. This may indicate that the early
loons are birds spending the night on Lake St. Clair (later loons may be
birds that spent the night on Lake Erie).
Percentage of Loons per 10 observation hours
|
Time (EST)
|
1992-94
|
1995-97
|
Total
|
|
0600-0700
|
1.5%
|
45.9%
|
29.1%
|
|
0700-0800
|
7.9%
|
22.0%
|
13.7%
|
|
0800-0900
|
33.5%
|
13.4%
|
19.5%
|
|
0900-1000
|
31.0%
|
5.4%
|
18.5%
|
|
1000-1100
|
10.8%
|
8.0%
|
8.5%
|
|
1100-1200
|
9.9%
|
5.3%
|
7.7%
|
|
1200-1300
|
5.3%
|
0
|
3.1%
|
Rouge
River Bird Observatory
Natural Areas
Dept.
University of Michigan-Dearborn
Dearborn, MI 48128
