Annual counts | Distribution (time of day, week) | Daily Mid-September |Changes (last 8 yrs) | Links | Articles | Sources | 2010 totals| 2017 totals

The former Chimney Rock Hawk Watch, founded by Christopher Aquila is now called the Washington Valley Hawkwatch since Chris left in 2017.

Most of the birders who were part of Chris' team are still there counting hawks in September and October on days with favorable weather for migration.

It is located at the eastern side of Washington Valley Park on the first range of the Watchung Mountains. It is accessible via a paved trail from the parking lot at the end of Miller Ln. off of Vosseller Ave. just north of Rt. 22 in Martinsville.

  On Sunday, Sept. 16 2017 the Somerset County Park Commission had a naturalist and park ranger there to help identify hawks. (tapinto.net article)

Counts are now reported at:
Washington Valley Hawkwatch - Month Summary | Hawk Migration Assiciation of North America's (HMANA) | hawkcount.org
and Somerset | eBird.org - look for "Chimney Rock Contingent" postings.
  Email: crhwatcher@gmail.com

  In 2017 after 26 years, Christopher Aquila, the founder of the Chimney Rock Hawk Watch, announced he was leaving to help his son, Gavin, establish a New Jersey Avian Migration Project Hawk Watch at Merrill Creek , which is nearer his home. So the name which was associated with Chris was changed.

It was one of the more significant sites in North America. Chris was the director of the hawk watch maintained by the Foundation for Avian Research and Education of NJ (FARE of NJ) Avian Migration Project. During it's heyday about 20 birders regularly staff the site from September 1st to November 1st. There are another 10-20 part time helpers. You can learn a lot by just standing around and listening to them call out sightings.

Old pages:
Chimney Rock Hawk Watch (www.crhw.org)
Chimney Rock Profile | Hawk Migration Assiciation of North America's (HMANA) | (hawkcount.org)

Maps: Martinsville, Washington Valley Park

These raptors (Hawks, Falcons and Eagles) are migrating from Canada and the Northern U.S. to destinations from Mexico to South America for the winter. See map at HawkMountain.org.

Many head south along the coast over Cape May NJ. Others turn west and fly over the Watchung Mountains where favorable wind currents assist them, then turn south when they get to eastern Pennsylvania. See migration below.

You will usually get 2-3 days between September 13th and 25th, where Large kettles of broad-winged hawks form over Chimney Rock, occasionally with 1,000 or more birds at a time and more than 7,000 in a day.
Hawks form "kettles" (called "boils" in NY) in thermal updrafts during migration. When they find a column of warm, rising air they stretch out their wings to rise with it. Other hawks see the kettle forming and join the crowd. The kettle grows and grows.
  As each hawk reaches altitude at the top of the thermal he sets his wings and glides away toward his destination.

Birds are usually more spread out during the Spring migration which peaks in early May. There is no Spring watch at Washington Valley.
See Birding | Visit Somerset County NJ

There are local groups of turkey vultures which just circle around the area; Novices frequently mistake them for hawks. The vultures are just hanging around, while the hawks and eagles are moving NE to SW.

There are several resident (nesting) red tail hawks, a coopers hawk and several peregrine falcons that over winter here. They do not migrate. You may see them occasionally.
There are also nesting eagles around (e.g. Duke Farms).

 
See other pictures in hobbies/bird_watching

Cumulative Total Sightings Excluding vultures
Year Total*  Year Total*
1993 20,727 2005 8,693
1994 17,184 2006 10,060
1995 19,545 2007 9,411
1996 31,564 2008 12,275
1997 18,127 2009 15,007
1998 18,727 2010 14,979
1999 23,075 2011 13,012
2000 28,379 2012 22,274
2001 9,763 2013 22,309
2002 13,241 2014 11,930
2003 6,214 2015 6,139
2004 10,635 2016 5,216
* Total includes migrating vultures starting in 2005.
Counts for the 3rd week in September
Most of the variability comes from Sept 14-25 which usually accounts for 40-70% of the total.

Sightings on any given day will vary considerably (from only a few to 4,000 or more) depending on wind direction. See wind below.
The median number of sightings for this time was 160; The average is about 1,000 because of a few very high days.

Note: There was speculation that because 2015 had the longest drought in Aug-Sep since 1996 there would be a big flight in this period, however it appears most of the broad-winged hawks went west of Chimney Rock.

Sept 22 was the bigest day in 2017 with 528 birds including 341 broad-wings.
A number of hurricanes this year may have upset the normal migration according to some birders.
Year 09-13 09-14 09-15 09-16 09-17 09-18 09-19 09-20 09-21 09-22 09-23 09-24 09-25 09/26-
10/5
10/6-
10/15
2017 6 7 7 75 164 528 45 93 16
2016 41 38 254 13 43 9 135 270 15 118 787 1,011 18 49 57
2015 72 206 543 161 19 6 5 1,123 842 124 37 18 18 295 797
2014 8 1,958 155 320 550 2,344 170 8 2 1,068 906 51 0 656 437
2013 426 2,370 4,449 8,738 1,095 34 42 20 44 584 275 218 395 984 566
2012 9 9 1,404 7,346 423 13 3,201 187 33 23 1,454 902 90 774 1,256
2011 166 41 64 2,961 4,584 265 21 28 6 26 0 36 147 1,724 618
2010 41 681 1,809 36 1,045 350 281 4,029 764 26 69 33 113 1,652 1,654
2009 173 1,266 2,876 58 111 1,626 3,674 210 10 34 27 309 866 698 1,800
2008 56 10 613 1,818 703 4,484 377 35 39 83 105 302 19
2007 140 17 770 3,703 83 135 18 20 24 3 345 110 59
2006 4 158 363 42 13 858 1,619 156 11 59 1,301 2,218 726
2003 0 10 7 160 113 59 26 51 296 27 32 154 163 2,627 1,255
2000 442 287 469 1,421 1,314 68 16 803 2,633 7,450 5 1,024 6,163 2,658 1,987
1996 7 704 668 144 449 5,018 17,491† 561 488 246 288 1,317 1,615
† There were 12,642 broadwings recorded in one hour on 9/20/1996. (SpeciesRecords | chimneyrock.s5.com)
The second highest day was Sept 10 in 1998 and Sept. 9 2017.

Year as of 9/25 Total for
year
Broad
winged
All
Others
Total Broad
winged
All
Others
Total Broad
winged
% of Total
1996 24,509 2,182 26,691 24,648 6,822 31,47078%
2000 20,140 2,299 22,439 21,558 6,821 28,37976%
2003 361* 1,077 1,438 1,938 4,647 6,585 29%
2007 4,424 4,942 9,366 47%
2010 8,041 1,950 9,991 8,337 6,755 15,092 55%
2011 7,403 1,304 8,708 7,639 5,373 13,012 59%
2012 16,130 1,950 18,080 16,392 5,882 22,274 74%
2013 17,895 4,414 22,309 80%
2014 6,260 1,700 7,960 6,472 5,458 11,930 54%
2015 2,413 948 3,361 2,420 3,719 6,139 39%
2016 1,879 1,231 3,110 3,804 1,412 5,216 73%
2017 1,180 414 1,594
(Including Vultures 2005-2010)
* In 2003 there were 1,487 broad-winged hawks between Sept. 30 and Oct. 3.

Note: Broad-winged hawks do not not like to fly over water so head west across ridges accounting for the large numbers here, (60-80% of the total). Broad-winged hawks are only 3% of the total in Cape May. Depending on wind patterns they may turn off north of Chimney Rock resulting in low broad-wined counts and low total counts.

Totals 1 thru 1996 1998 2000 2002 2003 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 20172
Sep 08 108 550 289 178 178 119 148 112 248 170 7696 412 286 62 211 -
Sep 15 1,574 4,354 1,542 874 357 754 1,269 990 4,609 3,165 634 4,408 7,696 2,541 1,008 631 494
Sep 25 26,691 11,859 22,439 8,810 1,438 5,176 5,769 8,955 11,534 10,000 8,708 18,080 19,141 7,960 3,361 3,032 1,320
Sep 30 27,399 12,909 24,711 10,125 2,768 6,843 6,486 9,405 11,850 10,379 9,246 18,646 19,737 8,160 3,452 3,110 1,533
Oct 15 29,623 15,416 27,075 11,603 5,320 8,101 8,291 10,826 14,032 13,104 11,050 20,110 20,691 9,113 4,453 3,901 1,801
Oct 31 30,984 18,195 28,175 13,107 9,110 11,424 14,474 14,544 12,791 21,337 21,664 11,1555,771 4,808
Nov 15 31,470 18,632 28,368 13,241 6,585 9,835 9,366 11,824 14,943 15,092 13,01222,274 22,309 11,9306,1395,216
Nov 30 § 31,564 18,727  
Highest two days 1996 1998 2000 2002 2003 2006 2007 2008 2009 2010 2011 2012 2013 2014 201520162017
Day Sep 20Sep 24Sep 22Sep 179/309/219/16Sep 18Sep 19Sep 20Sept 17Sep 16 Sep 16 Sep 18 Sep 20Sep 24 Sep 22
Count 17,923 5,353 7,450 4,128 1,151 1,619 3,703 4,484 3,674 4,029 4,584 7,346 8,738 2,344 1,123 1,011 528
Day Sep 19 Sep 10Sep 25Sep 2410/019/259/15Sep 16Sep 15Sep 14Sep 16Sep 19 Sep 15 Sep 14 Sep 21 Sep 23 Sep 10
Count 5,018 990 6,163 1,453 562 1,301 770 1,818 2,876 1,809 2,961 3,201 4,449 1,958 842 787 278
The second highest day was Sept 10 in 1998 and Sept. 9 2017.
§ Count stoped on Nov. 15 in recent years
1. Less vultures
2. Counts were spotty in 2017. They didn't start until Sept. 10. There were counts on the days with favorable weather.

Average hawks per day (2009-2013)

Note: The median number of sightings in the 3rd week of Sept. was 160; The average is about 1,000 because of a few very high days. See the daily totals above.


Flight Distribution (crhw.org)

Distribution by time of day

(For a day with 100 sightings)

5 Year average sightings per day (1997-2001)
WeekMedian/
Day
LowHigh
Sep. Wk1 26 2 203
Sep. Wk2 126 1 1933
Sep. Wk3 213 8 7450
Sep. Wk4 194 0 6163
Oct. Wk1 145 3 566
Oct. Wk2 77 1 448
Oct. Wk3 106 0 492
Oct. Wk4 44 0 419
Nov. Wk1 29 0 156
Nov. Wk2 7 0 354
Numbers vary widely depending on
weather. see below.

One day count distribuition for
Sep. 15-30
(Av. 1997-2001)
Count Days
1-19 1
20-49 2
50-99 2
100-199 3
200-499 2
500-999 3
1000-1999 2
2000-7500 1
Probabliliy
1-99 1/3
100-499 1/3
500+ 1/3

Wind:
Typically winds will be favorable the day after a front moves thru.
Winds blow counter-clockwise around an area of low pressure in the Northern Hemisphere. With this in mind, the wind direction before a cold front passes would usually be out of the south or southwest. After the cold front passes, the winds would shift to out of the west or northwest.
See Finding Cold Fronts Using Wind Direction: shift from south-southwest to west-northwest

The stronger the wind, the closer the hawks will fly to the treetops where substantially less air turbulence occurs, and the more easily the hawks will be seen.
A textbook viewing day for hawk watching will occur in Pennsylvania, New York, and New Jersey under the following conditions: the passage of a low pressure system to the north over the New England states; an advancing cold front moving south from Canada; the northwest winds for a few consecutive days. Under these conditions migration would occur along northerly facing slopes along the ridges.
When a high pressure system is positioned in the area, hawks disperse over large areas often resting and hunting while awaiting an increase in windspeed and thermals. As the high moves eastward, a southerly airflow moves in and hawks return using updrafts along south facing slopes.
Note: At Chimney rock, even with the south facing first range of the Watchung mountains, the counts are low with a south wind.
Source: Autumn Raptor Migration by Bill Streeter
Falcons (Peregrine, Kestrel, Merlin), with their sleek profile are not adapted for soaring flight, so are not affected by wind direction.

Counts by Wind Direction (Birds/Hr.)
W 65
WNW 92
NW 103
NNW 146
N 19
NNE 16
NE 159
E 285
SE 4
SSE 4
S 4
SSW 2
SW 6
WSW 34
Note: The table to the right above was created from data in early 2000 and shows higher counts with an east wind, however current common knowledge is that a NW wind is best.

Counts by Species: (thru 2005) (see changes below)
Species Highest 2000 Peak Dates Peak Hrs.
Broad-winged 24656 21588 9/14-9/25 9-5
Sharp-shinned 4597 3303 9/24-10/19 10-6
Am. Kestrel 2000 1514 9/23-10/19 10-6
Red-tailed 908 127 10/29-11/10 10-4
Osprey 945 598 9/15-9/28 9-6
Cooper's 564 395 10/10-10/19 10-5
N. Harrier 474 199 9/13-10/10 10-5
Red-shouldered 401 109 10/10-11/2 10-3
Merlin 338 277 9/13-10/11 11-7
Bald Eagle 110 94 9/13-9/20 9-6
Peregrine Falcon 113 64 10/3-10/10 10-5
Golden Eagle 18 9 10-19-22 12-5
N. Goshawk 15 1 10/20-11/7
Rough-legged 3

Decline - Trends

Species
Chimney Rock (Average birds per year)
Cape May *
1996-20002004-2008 Decline/
Increase
% of total
(2004-8)
Decline/
Increase
Average # % of total Average # % of total
Broad-winged 15,688 65.6% 5,980 53.5% -62% 3% -54%
Sharp-shinned 3,876 16.2% 2,458 22.0% -37% 45% -47%
Am. Kestrel 1,724 7.2% 779 7.0% -55% 13% -48%
Osprey 733 3.1% 468 4.2% -36% 6% -49%
Cooper's 475 2.0% 467 4.2% -2% 15% 32%
N. Harrier 278 1.2% 213 1.9% -23% 3% -40%
Merlin 276 1.2% 197 1.8% -29% 5% -25%
Red-shouldered 242 1.0% 184 1.6% -24% 1% 4%
Red-tailed 271 1.1% 155 1.4% -43% 5% -48%
Bald Eagle 90 0.4% 129 1.2% 44% 0.8% 46%
Peregrine Falcon 77 0.3% 98 0.9% 27% 4% 0%
Golden Eagle 11 0.05% 14 0.13% 31% 0.05% -19%
N. Goshawk 7.0 0.03% 2.4 0.02% -66% 0.1% -48%
Rough-legged 1.2 0.01% 0.6 0.01% -50% 0.002% -82%
Unidentified
Raptor 86 0.4% 16 0.1% -82%
Acciptor 42 0.2% 11 0.1% -75%
Buteo 19 0.1% 5 0.0% -72%
Falcon 12 0.1% 5 0.0% -58%
Total 23,909 11,182 -53% 33,511 -39%
* Cape May % of total: 2004-2008; Decline: 1996-2000 vs 2004-2008. See Cape May page
Sources: chimneyrock.s5.com by John Kee
      Hawk Migration Assiciation of North America's (HMANA) hawkcount.org

The declines vary by species.
Broad-winged hawks, Sharp-shinned hawks, American Kestrels, Osprey and Red-tailed hawks had the largest declines of 44-60%.
Cooper's hawks increased. Bald eagles have increased by about 45% as they continue to recover from their decline due to DDT (1946-1972), loss of habitat and hunting.
Osprey's are frequently hunted in Mexico.

Most others declined in the 25-25% range.

There are a variety of factors which more experienced birders have proposed to account for the decline. I couldn't find any definitive studies.

See:
- Species trends at chimney rock
Bedford Audubon Society - Chestnut Ridge Hawk Watch 2001 - Species Accounts
2013 Regional Trend Summaries and Conservation Assessments | Raptor Population Index (RPI)
Raptor Population Index (rpi-project.org/2009report/)
- Species Records thru 2005 by John Kee
- A Five Year Analysis of Autumn Hawk Migration at Chimney Rock, Martinsville, N.J. (1990-1994) , by Christopher D. Aquila & Steven B. Byland
"Using Autumn Hawk Watch to Track Raptor Migration and to Monitor Populations of North American Birds of Prey" - Article on Sharp Shinned migration decline - USDA Forest Service Gen. Tech. Rep. PSW-GTR-191. 2005

Demography and Populations -- Sharp-shinned Hawk -- Birds of North America Online at Cornell says:. (Requires subscription: $5/mo, $42/yr)
"Sharp-shinned hawks are the most difficult accipiter and among the most difficult birds to census in North America."
"Declines in counts at migration watchsites in e. North America from 1940s to early 1970s almost certainly due to widespread use of DDT."
"Declines in the 1980s and early 1990s initially were attributed to various factors acting singly or in concert: environmental contaminants (mainly organochlorines), migratory short-stopping, natural population cycles, depressed populations of Neotropical migratory prey species, and the aging of eastern forests. Recent analyses of concurrent Christmas Bird Count data from the region, however, have revealed significant increases in numbers of Sharp-shinned Hawks overwintering in areas north of the watchsites in question (i.e., e. Canada and the ne. U.S.), strongly suggesting that the declines are due to migratory short-stoppingÑperhaps the result of increased use of bird feeders as hunting habitat by sharp-shinsÑand not to an overall decline in eastern populations (Dunn and Tessaglia 1994, Duncan 1996, Viverette et al. 1996)."
Viverette, C. B., S. Struve, L. J. Goodrich, and K. L. Bildstein. 1996. Decreases in migrating Sharp-shinned Hawks at traditional raptor-migration watchsites in eastern North America. The Auk 113:32-40.

Conservation Status Report - Sharp-shinned Hawk, 2007 at HawkMountain.org states:
"From 1974 to 2004, migration counts declined a statistically significant 1.1 % per year at Hawk Mountain Sanctuary, Pennsylvania and 4.5 % per year at Cape May Bird Observatory, New Jersey."
"The decline in numbers at Cape May might indicate declined reproductive success, as most individuals counted at Cape May Point are juveniles."
"The discrepancy between migration trends (lower) and those from CBCs (Christmas Bird Counts) (higher) may be due to migratory short-stopping."

Fall Raptor Migration over Lake Erie Metro Park (increasing)
State of the Birds - The 2009 Report from the Interior Dept. shows that Wetland birds are increasing while Grasland and Aridland birds are declining.

Saving Migratory Birds for Future Generations: The Success of the Neotropical Migratory Bird Conservation Act, Compiled by American Bird Conservancy, May 2009

A Feb. 2009 Audubon Society study found that more than half of 305 birds species in North America, a hodgepodge that includes robins, gulls, chickadees and owls, are spending the winter about 35 miles farther north than they did 40 years ago.
Over the 40 years covered by the study, the average January temperature in the United States climbed by about 5 degrees Fahrenheit, which they speculate may be the reason. (Hawks were not mentioned in the summary I saw.)

Potential Impacts of Global Climate Change on Bird Communities of the Southwest by Charles van Riper III, Mark K. Sogge, and David W. Willey Biological Resources Division U.S. Geological Survey

Species mix Chimney Rock vs Cape May:
Buteos (Broad-Winged hawks in particular) like to exploit updrafts off of ridges, hence the large numbers at Chimney Rock on the first range of the Watchung Mountains.
Falcons (Peregrine, Kestrel, Merlin) rely more on their own powers of flight and do not need mountain updrafts.
Accipiters (Sharp-shinned, Coopers Hawks, ...) and falcons tend to follow the shorelines, hence higher counts at Cape May.

Other Hawk Watch Sites:
Counts are for Fall only.
Site Location Median
Fall
Totals
2002
Total
Cape May Cape May, NJ 50,00035,267
Hawk Mountain Kempton, PA 20,00021,708
Chimney Rock Martinsville, NJ 19,00013,241
Montclair Montclair, NJ 12,00011,340
Militia Hill Fort Washington State Park, PA 9,000  
Wildcat Ridge Hibernia, NJ 9,000 7,011
Racoon Ridge Blairstown (Hemlock Glen), NJ 15,000 * 4,238
Scotts Mountain, Merrill Creek Washington, NJ 9,000 8,737
Sunrise Mountain Stokes State Forest, Branchville, NJ   * 4,678
Bake Oven Knob Germansville, PA 20,778
(Median 1998-2002)
* Racoon Ridge only counted for 9 days in Sept. 2002
* Sunrise Mountain only had counts for 13 days in Sept. 2002
Some sites keep Spring totals also (Feb-May) which are about 1/3 of Fall totals.
Other New Jersey sites at: New Jersey Sites, Hawk Migration Assiciation of North America (HMANA)
and the JerseyBirds mail list.

Scherman-Hoffman Wildlife Sanctuary (New Jersey Audubon Society)
Bernardsville, (908) 766-5787






Migration:
TyBroad Broad-winged hawks migration:
Sept. 10 - Lake Ontario
Sept. 15 - Mass.
Sept. 17 - NJ and PA
Oct. -1   - Texas
They may not fly on some days because of weather or the need to refuel so the average from above is 65-90 miles per day.
Red-Tails and others tend to be later.

Hawks will fly around 10 hours per day and travel from 100 to 250 miles. Ducks and geese might travel as much as 400 to 500 miles per day.
Many species of wading and swimming birds are able to feed at all hours, they migrate either by day or night. Soaring birds such as broad-winged hawks only migrate during the day to take advantage of thermals.

In some species of raptors, every individual migrates. In other species, only part of the population migrates and some individuals remain on the breeding grounds. Other species are completely sedentary. Overall, about 45 percent of all raptor populations migrate.

Raptors fly from 29-40 MPH at an elevation of 700 - 4,000 ft.

Migration may have as much to do with availability of food as weather.
See also Migration Path | Hawk Mountain Sanctuary

Wintering locations:
Broad-wings Central America and N. South America
Sharp-shinned Southern US, Central America
Coopers Gulf coast, Mexico to Honduras
Kestrel Coastal Mexico, Central America
Ospreys, Peregrine falcons Pacific coast of S. America & Bolivia
See:
Flyways And Byways at 10000birds.com
New Jersey Osprey Project
Tails of Birding: Where Do the Hawks Go?
Random House Atlas of Bird Migration: Tracing the Journey's of the World's Birds, 1995

Terms:
BBS - Breeding Bird Survey
CBC - Christmas Bird Count

Articles
- John Kee - Species Records thru 2005
- Christopher D. Aquila & Steven B. Byland - A Five Year Analysis of Autumn Hawk Migration at Chimney Rock, Martinsville, N.J. (1990-1994)
- Kyle McCarty and Keith L. Bildstein - "Using Autumn Hawk Watch to Track Raptor Migration and to Monitor Populations of North American Birds of Prey", USDA Forest Service Gen. Tech. Rep. PSW-GTR-191. 2005
- Robyn Worcester, Ron Ydenberg - Cross-Continental Patterns In The Timing Of Southward Peregrine Falcon Migration In North America, 2008,
- Johnd Elong, Stephen W. Hoffman - Differential Autumn Migration Of Sharp-Shinned And Cooper's Hawks In Western North America

Links
Other Links:
Current Counts at Hawk Migration Assiciation of North America's (HMANA) hawkcount.org (NJWMP at Chimney Rock)

Bird Watching Here
Cornell Lab of Ornithology
  Cornell's All About Birds
The Hawk Conservancy Trust
Data entry overload? Learn eBird tricks and tips! - eBird.org
Binoculars,
Birding and Raptors in Northwest New Jersey at www.njskylands.com
Bird Watching in hobbies
Squirl Proof Bird feeders
Autumn Raptor Migration
NPWRC :: Migration of Birds

Sources:
chimneyrock.s5.com John Kee.
www.crhw.org, chimneyrock.s5.com

2017 counts:
8, 9, 10, 11, 12, 15, 16, 17, 20, 21, 22, 8/21, 9/22,

See also:
Washington Valley Park Hawk Watch | SomersetCountyParks.org
Chimney Rock Quarry
25 Nature Spectacles in New Jersey, by Joanna Burger and Michael Gochfeld

Hawk Watch | Somerset Co. Park Comission


Return to: Martinsville Information

last updated 25 Oct 12. 2017