Date: 4/29/18 8:04 am
From: Nick Bolgiano <nickbolgiano...>
Subject: 2018 Tussey Mt hawk watch summary
2018 was the 18th season of the spring hawk watch at Tussey Mt, staffed Feb
20-Apr 25. The watch site is located on the boundary between Centre and
Huntingdon counties in the western Ridge-and-Valley province. Our primary
focus is to monitor the spring golden eagle migration that is concentrated
in this region.

The official hawk watch counter was Henry Hvizdos from the Cleveland area.
Counts were conducted on 55 days, with 408.5 hours of watching. Our effort
was very good and on par with previous seasons.

For the second consecutive year, some of the season’s warmest temperatures
were experienced in February. The temperature on Feb 20-21 reached 70
degrees Fahrenheit, a level not encountered again until Apr 13.
Temperatures during March and most of April were considerably below
average, with persistent W and NW winds. There were only a few days with
favorable S or SE winds. The reason for this weather regime was a
persistent high pressure system in NE Canada, causing the jet stream to
form a southern-bending trough in the NE United States. I believe that this
weather explained much of our 2018 observations.

Season totals are shown below, along with 10-year averages (2008-2017):

*Species*

*2018*

*10-year average*

Golden eagle

150

198

Osprey

53

85

Bald eagle

84

44

Northern harrier

25

28

Sharp-shinned hawk

99

180

Cooper’s hawk

7

48

Northern goshawk

0

2

Red-shouldered hawk

32

49

Broad-winged hawk

381

585

Red-tailed hawk

174

368

Rough-legged hawk

0

4

American kestrel

34

40

Merlin

4

5

Peregrine falcon

1

2



The 150 golden eagles were 76% of the 10-year average (although 2008-2017
included eight of the top nine GE season totals). Previous season totals
included 150, 152, and 156 golden eagles, so the 2018 total was at the low
end of the normal range. The most notable aspect of the golden eagle flight
was its scattered nature. The Feb total of 31 was the second highest for
the month. The 15 golden eagles on Mar 30 was by far the lowest and latest
daily maximum in our 18 years.

In the fall, the vast majority of golden eagles observed at Pennsylvania
watch sites primarily use wind updrafts off a ridge, as their migration
concentrates well after the fall equinox when thermals are weak. Reliance
on ridge updrafts is true in the spring when it is cloudy, but on sunny
spring days, golden eagles use thermals to a much greater extent than in
the fall, as spring migration is around the spring equinox. They become
much more difficult to find when they rely on thermals. One such day when
we may have missed many was Feb 27, when we observed 12 high-flying golden
eagles late in the day. I suspect that this was the biggest flight day of
the season, but most were too high to see.

The 84 bald eagles exceeded the previous season high of 65 (2015); the
number of local bald eagles also increased substantially over previous
years. The numbers of other migrating raptors were mostly below average,
particularly for sharp-shinned and red-tailed hawks. This was only the
second year that we missed rough-legged hawk.

Thanks to all those who contributed, including Shaver’s Creek Environmental
Center, the State College Bird Club, and individuals for funding.
Nick Bolgiano
State College
 
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