HawkWatch Update Archive - 2005

Visitors search the sky for hawks.

Cadillac Mountain is a great spot to search for migrating hawks.

NPS/Lora Haller

October 9, 2005. HawkWatch officially ends on Wednesday, October 12, although it is unlikely that the weather will allow us to spend the last few days on the Cadillac summit. For the past week there have been days with severe wind gusts, driving rain, and zero visibility, and some days with warm, clear weather but a steady southwest wind. For these reasons, no migrating raptors were sighted this week from the HawkWatch site. Not one. From the birds’ perspective, they must fly thousands of miles in a short time, so it is probably worth the extra time to wait out a storm rather than exert too much precious energy in order to gain mileage.

If a migratory bird is constrained from normal migratory behavior (such as several weeks of poor weather or a captive wild bird), that bird will exhibit zugunruhe, a German term for restlessness, during this period. Many experiments have been conducted to better understand this phenomenon. One famous experiment involved indigo buntings in a bowl-shaped cage with an ink pad at the base, blotter paper along the sides of the bowl, and screen covering the cage so the birds could see. In a planetarium, a regular autumnal star pattern was projected and the birds consistently hopped toward the south, as shown by the black foot prints on that side of the paper. When the star pattern was artificially altered, the buntings would still hop towards the simulated southerly direction. This proves that some birds may use the stars as a map when they travel at night. Migrating birds may also employ geographic landforms such as mountain ridges or the Atlantic coastline, use the sun as a compass, or even possess an internal magnetic compass in order to find their way to a specific southern destination and return again in the spring. It is truly a remarkable feat that is not fully understood.

As HawkWatch comes to end, we reflect upon the few great days when several hundred birds were sighted, some flying close enough to see if they were carrying food in their talons. At Acadia, our HawkWatch believes in quality, not quantity. There were a number of slow days when not many raptors were flying, but this allowed us to reinforce our identification abilities and speak about the conservation aspects of these marvelous creatures. I would like to thank all the HawkWatch contributors: raptor ranger Lora Haller; volunteers Barb and Gerry Mulligan, Tony Linforth, and Jim and Kathy Zeman; and all of the ‘fair-weather birders’ on Cadillac. Thanks for a great season! May the sun always be on your face and wind at your back.

-Todd Larsen

October 2, 2005. The month of September ended on a high note with over one thousand migrating hawks spotted in the last week (we still like to boast about our record day of over 700 birds on Saturday, September 24). October, however, has had a slow start, mainly due to inauspicious conditions such as south winds and foggy days. These winds may redirect many raptors farther inland as they fly south, and these raptors are not visible from the HawkWatch site on Cadillac Mountain. If these conditions persist, most of the migrants will pass us by during this peak period.

In comparison to previous years, we have exceeded the average number of migrating hawks seen during the fall HawkWatch with over 2,500 hawks compared to the average of approximately 2,400, and there is still over a week and a half until it concludes! HawkWatch at Acadia typically runs from August 22 until October 12, which is when the greatest number of birds are passing through this area. However, there are still several dedicated people that come up Cadillac later in the fall to catch the stragglers. Last year in late October, a couple of experienced birders observed a golden eagle (very rare in Maine) and a rough-legged hawk, which is an occasional winter resident.

All of the data we collect is entered into a database along with data from many other HawkWatch sites in North America. These statistics can show trends over several years and help ornithologists with population censuses. For example, numbers of bald eagles and peregrine falcons have increased due to protection and the ban of pesticides such as DDT. American kestrels, on the other hand, have faced a small decline in numbers due to the loss of their nesting habitats in tree cavities because many private woodlot owners cut down dead trees. Check to see if there is a HawkWatch site near your hometown and, if so, what species and quantities they are seeing. The best place to be now is at the Acadia HawkWatch site on the North Ridge Trail near the Cadillac summit—lots of hawks, great company, beautiful view, and warm weather.

-Todd Larsen

September 25, 2005. Do birds of a feather flock together? Not necessarily, unless you are referring to broad-winged hawks and more specifically those hawks flying on the historic date of September 24, 2005, when the fortunate few people on Cadillac Mountain were witness to a record number of migrating raptors at Acadia. An average day at HawkWatch in Acadia may yield approximately 60 birds…On Saturday, 713 birds were sighted in seven hours! This breaks the previous one-day record of 671 birds set in 1995 when HawkWatch just started. This huge number was mainly influenced by a great amount of broad-winged hawks—483 in one day!

Broad-wingeds belong to the buteo family of hawks, characterized by a heavy body, a short tail, and large, broad wings. This body shape allows these birds to easily exploit thermals, updrafts, and wind currents as they commonly soar to gain altitude. Flocks of migrating broad-wingeds may consist of a couple of individuals or several thousand birds as they seek out energy-saving thermals, which they circle up in like a spiral staircase, then glide down to the next updraft. Although 500 of this one species is considered a big day in Maine, HawkWatches farther south encounter much larger numbers, such as Hawk Mountain in Pennsylvania with thousands of birds, or Corpus Christi, Texas, with hundreds of thousands of broad-wingeds in a single day!

Saturday was a great hawk-watching day because after a lull of a couple of weeks due to rain, fog, and southerly winds, many migrating birds were simply waiting for a strong north wind and clear skies to help them along their way down south. This bottleneck created a large concentration of raptors when the conditions were fit for flying. The last half of September is usually the best time of year to observe this amazing migration pattern, so this week should also be productive if the winds are right.

HawkWatch is situated on the North Ridge Trail, 200 meters from the Cadillac Mountain summit. If you haven’t already checked it out, come see what you have been missing!

-Todd Larsen

September 18, 2005. During the past five of seven days, from September 12 to 18, HawkWatch was not conducted on Cadillac Mountain due to rain, fog, and low visibility. On days like that, the birds are probably not migrating because of the inclement weather. Instead, they may rest in a sheltered valley and increase their energy and fat reserves by hunting for food. Since hawks may lose 40% of their weight or more during this long and arduous journey, it is important that they stock up well before the trip and do not unnecessarily waste their energy.

Since these raptors are flying primarily from north to south, a strong wind from behind them helps to push them along. If the prevailing winds are blowing from the south or southwest, the birds may decide to “hunker down” for a few days and wait for more optimal conditions. However, some birds will fly into the head-winds, but usually along a less direct route. Smaller species such as sharp-shinned hawks and American kestrels will follow ridgelines and treetops to avoid the stronger winds. At the HawkWatch site on Cadillac, we see these birds flying low in the valley as they adhere to topographical features on their way around the mountain, much like a tacking sailboat as it maneuvers around islands. As a general rule, we expect to see more birds when the wind is blowing from the north than the south.

Although this past week had a low bird count of 63 (in two days), this time of year has historically been the most successful. At Acadia National Park, the last few weeks in September are the time when most of the migrating hawks are passing through. The highest recorded hawk count last year was on September 21 with 497 raptors sighted. Maybe we can beat it this year! Join us every nice north wind day from 9 a.m. to 2 p.m. at the HawkWatch site, 200 meters down the North Ridge Trail from the top of Cadillac Mountain.

-Todd Larsen

September 12, 2005. This has definitely been an exciting year for birding enthusiasts at HawkWatch on Cadillac Mountain. In the last three weeks, we have counted almost 1,300 individual birds of prey as they migrate south for the winter. Last year at this time, only 350 birds had been sighted! In an average year in Acadia, from August 22 to October 13 between 2,500 and 3,000 birds are seen. Although this number is much lower than more famous hawk observatories such as Cape May or Hawk Mountain, we feel that quality is more important than quantity. We often see birds within 30 feet of the HawkWatch site, and for many of the sightings binoculars are not needed (but do indeed help) for noticing the red tail and wing “lights” on the American kestrel, or distinguishing the fine details between sharp-shinned and Cooper’s hawks. The view of Bar Harbor and Frenchmans Bay is also astounding.

Our biggest day of the year was on September 10, with 307 birds seen in seven hours. A large kettle of 30 broad-winged hawks was seen on this day, as well as a large quantity of American kestrels. This week, sharp-shinned hawks were again the most frequent migrants with 285, followed closely by kestrels at 202, as well as 112 broad-winged hawks, 55 osprey, and 20 northern harriers.

These raptors are mostly migrating between the hours of 9 a.m. and 2 p.m. when thermals of rising air are most prominent and tail winds are strongest. They may hunt along the way, but most are probably feeding in the morning or late afternoon. Raptors as a whole have a wide variety of food preferences, from the insect-loving kestrel, to the bird-eat-bird world of the peregrine falcon. Osprey are principally fish eaters, the accipiter family (including the sharp-shinned hawk) and falcon family are bird eaters, and the buteo family (including the broad-winged hawk and red-tailed hawk) are generalists, eating insects, reptiles, birds, and/or mammals. Remember to keep your birdfeeder well stocked this fall because it not only feeds small migrating song birds, but also the larger raptors that require a quick and easy meal.

The Acadia National Park HawkWatch site is on the North Ridge Trail, only 200 meters from the summit of Cadillac Mountain. Feel free to bring a chair, lunch, and binoculars to enjoy this marvelous exodus.

- Todd Larsen

September 5, 2006. As summer at Acadia begins to wind down, the fall raptor migration flourishes! During the week of August 29 to September 5, there was a rapid increase in the number of hawks counted up on Cadillac Mountain. After Hurricane Katrina’s last breath blew through here from the south, the winds gradually switched directions in order to give the migrating raptors a tailwind to ride on from the north. Since the birds had been waiting out the storm, there was a build-up, and we saw higher concentrations as the winds became more favorable for the southbound flight.

The most common raptor seen from the HawkWatch site is the sharp-shinned hawk, with over 200 individuals spotted in the last five days! “Sharpies” are about the size of a blue jay and, even with binoculars, can only be spotted if they are within about a mile of the observer. Think of how many slip by out of visual range! However, we do get amazingly close looks at these normally reclusive birds as they fly low over the treetops and ridgelines. Their “flap-flap-glide” flight pattern is characteristic of these accipiters because of their small, rounded wing shape.

Another frequent species is the American Kestrel, with almost 60 seen in two days. These falcons often travel in pairs. The male is especially colorful with a red tail, grayish-blue wings, and a black face mask.

The weather is definitely the best indicator of the numbers of hawks to expect for the day. On a warm, sunny day with a steady northerly wind, many hawks will most likely grace the skies. In the past two days, there were over 250 migrating raptors taking advantage of these optimal conditions.

The Acadia HawkWatch site is on the North Ridge Trail, only 200 meters from the summit of Cadillac Mountain. Feel free to bring a chair, lunch, and binoculars to enjoy this marvelous exodus.

- Todd Larsen

August 29, 2005. The raptors from the north have begun long annual journeys to their wintering grounds. HawkWatch officially started on Monday, August 22, on the North Ridge Trail of Cadillac Mountain. From this site for the past week, more than one thousand visitors have had life-altering experiences (or just came to look at the pretty sailboats) as they watched in awe while majestic birds of prey soared effortlessly over their heads.

It truly has been exciting, as we have seen 109 individual raptors from 10 different species (11 species if turkey vultures are considered raptors). Of these, the most commonly seen birds were sharp-shinned hawks with 37 individuals sighted, 31 turkey vultures, 7 osprey, and 7 red-tailed hawks. As the days become shorter and colder, we expect these numbers to increase dramatically.

Although we never know what may blow over the mountains of Acadia, past experience shows that a steady wind from the north/northeast “pushes” the greatest concentration of migrating birds. Raptors travel great distances during the day when tail-winds are stronger and when the heat of the sun creates updrafts (thermals) of warmer, rising air. These thermals are not visible, but fluffy, flat-bottomed cumulus clouds are usually created due to rising warm air that condenses at colder and higher altitudes. You can often see several soaring birds taking advantage of these vertical updrafts to gain elevation without expending energy by flapping their wings.

Please join Raptor Ranger Lora Haller, Tony Linforth, Jim Zeman, Gerry and Barbara Mulligan, and myself on the North Ridge Trail (200 yards north of the Cadillac Mountain summit) every good visibility day from 9 a.m. to 2 p.m. until mid-October to witness a fraction of the amazing journey that these birds endure as they head south. You can check the weather beforehand (remember, good visibility and NE winds) at the National Weather Service website. The Acadia hazecam shows the latest visibility levels. We input our HawkWatch data at www.hawkcount.org. But nothing beats seeing these birds as they soar high over Bar Harbor and Acadia National Park.

- Todd Larsen

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