HawkWatch Update Archive - 2006
October 10, 2006. The official hawk-watching season here in Acadia is drawing to a close. The last day we will be up there this year is Wednesday, October 11, 2006. Some hawks will still be passing through after that date, just generally not in concentrations as high as earlier in the season. Also, more northern species, such as the northern goshawk and the rough-legged hawk, tend to migrate later in the fall, so a few more of those would be coming through as well. On average we see nearly 2,500 hawks pass through in a season, and this year has been no different with 2,443 total migrants as of today. However, some species numbers have been drastically different from their seasonal averages. Both sharp-shinned hawks and American kestrels are below their seasonal average here by around 200 birds. On the other hand, we saw almost double the number of broad-winged hawks that we usually do. And peregrine falcons were up as well, with 23 darting past—nearly double their typical average! We also saw an exciting seven peregrines migrating past on September 16, which is a new daily record! We have further seen our first (and perhaps only!) northern goshawk of the season on October 5.
It may be nearing the end of hawk-watching here in Acadia, but more southern HawkWatch sites should still have lots of action going on. For instance, yesterday at the famed bird-watching locale of Cape May, New Jersey, 1,239 hawks (mostly sharp-shinned and Cooper’s) migrated through. In Kiptopeke State Park in Virginia, they saw 3,957 migrants yesterday. Their count was comprised primarily of sharp-shinned hawks, but also of hundreds of Cooper’s, broad-wings and kestrels, along with some other species. These numbers also demonstrate how the numbers of migrating raptors seen daily increases almost exponentially the further south you are. Here in Acadia we only see some of the birds that are summering north of us, which doesn’t comprise an extensively large area. But more southern HawkWatch sites are seeing a greater accumulation of birds coming from a larger part of North America. Perhaps the most incredible place to see raptors is in Veracruz, Mexico, at the ‘River of Raptors’ HawkWatch. At this location, hawks that have been following the coastline south and are continuing to Central and South America are literally funneled over the relatively small strip of land at the southern tip of Mexico. On October 7, almost half a million raptors were seen passing through in just one day! Usually at least half of their numbers consist of broad-winged hawks on their way to South America. Swainson’s hawks also make up a large percentage, as do turkey vultures. They also see hundreds of kestrels, osprey, sharp-shinned and Cooper’s hawks, and a bunch of hawks that we don’t see this far north—kites like the Mississippi kite and swallow-tailed kite. So if you still have an itch to see more birds of prey, a great place to check for a HawkWatch location near you or wherever you are traveling is at www.hawkcount.org. That is also the site where we report our migration numbers, and visitors are able to check out our data as well as data from HawkWatch sites around the country.
Well, it has been a great season here in Acadia, and I’ve truly enjoyed watching not only the hawks but also the other wildlife and the beautiful scenery here in this spectacular place. This is the last edition of Riding the Winds for the year, but whether you are a tyro just learning the ropes or a seasoned regular identifying specks in the distance, hopefully you can join fellow hawk-watchers on Cadillac next fall for HawkWatch 2007!
October 3, 2006. There have certainly been some memorable moments during this hawk-watching season on Cadillac. Unlike many other HawkWatch locations, we are often granted intimate views of these beautiful aviators. There is nothing like watching a gorgeous male kestrel dart past, with its red tail and blue wings gleaming in the sun. We have seen a sharp-shinned hawk dash after a songbird not 50 feet from us. One day, a stately adult bald eagle soared right overhead. Its magnificent size and contrasting colors were amazing to observe so close. Many osprey have offered equally thrilling views as they glide past, occasionally flapping their great wings and hardly giving us a passing glance with their fierce yellow eyes. Although perhaps not as impressive as at more southerly HawkWatch locations, it is still incredible to see kettles of soaring broad-winged hawks rising up on a thermal. With sometimes 20 to 60 birds circling up in a column of warm air, they look like a little tornado of hawks! We have seen feisty merlins antagonizing kestrels and stunning northern harriers that have come so close we can see their owl-like face. It is not too late to witness some of these breathtaking displays, so be sure to stop in at the HawkWatch site before the migration winds down for the year!
Featured raptors of the week:
Osprey – The osprey eats fish almost exclusively. The underside of its talons has barbed pads that are akin to coarse sandpaper, which make it easier for the osprey to grasp slippery fish. When the osprey flies with its prey, it usually holds the fish headfirst to make it more aerodynamic. The osprey builds huge stick nests in conspicuous places, such as on telephone poles that are often visible along highways. They also use trees, platforms,and even channel markers, and usually nest near water. People often confuse their nests with those of the bald eagle, but bald eagles use large trees almost exclusively and would not use a platform or telephone pole. Bald eagles tend to nest in more forested areas, but also near water.
Tips for in-flight identification: The osprey is a large bird with a 5-6 foot wingspan. Its long wings look almost droopy in flight. It tends to bend its wings back slightly at the wrist so that when soaring overhead, it appears to fly in an M-shape. It is very dark above, with a whiteface and belly below, and the dark eyestripe may also be visible. Underneath,its wings are white with dark patches and dark wing tips.
Northern Goshawk – The northern goshawk is the largest accipiter, and its name stems from ‘goose hawk.’ We have yet to see any northern goshawks migrating through, but this is not unusual. Goshawks are a more boreal species and can be found in Canada,the northern U.S., and the Rockies year-round. Some do migrate, however, though not even as far as the southern United States. We only see a handful migrate past on average each year, although a few more probably migrate through after the official end of our HawkWatch season. Still, we do have pairs that live and nest in the park. Goshawks are known for their vigorous defense of their nests and aggressive behavior. They do not hesitate to attack people and other animals that venture too close to their territory, and unwary visitors and park employees have been harassed occasionally by a couple of this year’s juveniles.
Tips for in-flight identification: The goshawk is large, with a fairly long tail, and may appear butte-like when soaring. Adults are very gray, but darker gray above and lighter below. Juveniles look similar to juvenile Cooper’s hawks, with brown backs and streaked under parts.
September 26, 2006. Last week was not particularly favorable for hawk-watching due to the weather. However, on Monday, September 25, we made up for it with an exciting 376 migrating birds of prey! Although watching hawks is awe-inspiring, we also conduct the HawkWatch annually to census the raptor populations. Of course there is major variation between years, due in part to the weather and whether or not the migrants fly within our range of view. This means that the numbers at a particular HawkWatch site would be different from year to year even if the raptor populations were exactly the same. However, we enter our data into a database maintained by a non-profit organization Hawk Migration Association of North America (HMANA), which collects data from numerous HawkWatch sites around the country. Using the data from all of these sites, biologists and statisticians are able to determine regional and national population changes over time.
Most of the raptor populations seem to be either stable or increasing since the major population reductions between the 1940s and early 1970s due to the use of DDT. By the late 1960s people realized there was a problem with some raptor populations—and it was almost too late. Therefore, it is important for us to continue to monitor the numbers of hawks that we see, so we are better able to prevent the loss of species.
Featured raptors of the week:
Peregrine Falcon – Peregrines are most likely the fastest animal on earth. In normal flight, they often obtain speeds of around 60 mph (most songbirds fly at speeds of 20-30 mph). And when they are diving after their prey, they may reach speeds of up to 200 mph! Peregrines are well adapted to fast flight. Not only is their body compact and aerodynamic, but also they have a special structure in their upper mandible or beak called a baffle. It is a little peg in the nostril that is thought to deflect the air stream slightly so that the birds are able to breathe when diving at such a high velocity.
Tips for in-flight identification: The peregrine is a ‘chunky’ falcon in comparison to the merlin and American kestrel. It is not as dark as the merlin and does not get knocked around in the wind like the kestrel. They have a dark head and mustache. Juveniles exhibit vertical streaks on the underside, while adults have a light-colored breast and vertical barring.
Northern Harrier – The northern harrier hunts for its prey both by sight and sound. It has an owl-like head with a facial disk and stiff feathers around its face to help transmit sound. Also, while most raptors have only one mate for a breeding season, male harriers may mate with up to five other females and provide most of the food for all of those females and the young in each nest.
Tips for in-flight identification: The harrier tends to hold its wings in a slight dihedral (upward angle) when soaring. It has a long tail and a bright white patch on its rump. Males are light gray above, while females and juveniles are brown. Underneath, males are almost entirely white, except for black wing tips and trailing edge of the wings. Females and juveniles have streaked bellies and barred wings.
September 19, 2006. Well, the season’s migrating raptor total is up to nearly 1,500 birds so far! It is incredible to think of that many birds of prey flying past us in only a month. As we watch these beautiful raptors soaring overhead, heading to their southerly destination, visitors often want to know where they are going. The answer is as varied as there are species and individual birds. In general, some species, like the American kestrel and red-tailed hawk, only go as far as southern New England. Others, like the merlin and osprey, go a bit further, to Florida and the Caribbean. At the extreme end, most broad-winged hawks over-winter in the tropical forests of South America.
So how do these birds find their way over such a great distance? In many instances it seems that the raptors are following major north-south land formations, such as the coastline, the Mississippi River, or mountain chains like the Appalachians. This results in major flyways, or migration routes, which are great places to watch for migrating raptors. Some other bird species (not necessarily raptors) have the mineral magnetite in their heads and can use the earth’s magnetic field as a compass to direct their migration. Night-flyers, like most passerines and geese, may rely on the position of stars and constellations to guide their way, while in other cases it is a learned or instinctual route. However they do it, migrating hawks are an exciting sight to observe!
Featured raptors of the week:
Merlin– The merlin breeds primarily in Canada, northern Maine, and the northwestern United States. They are one of few raptor species which will make long water crossings during migration. This species was nicknamed the pigeon-hawk, not only because it may prey on pigeons, but because its “rowing” flight resembles that of a pigeon.
Tips for in-flight identification: This falcon is very dark in comparison to the other falcons, although males are lighter than females and juveniles. It is heavily streaked below, with checkered underwings, a pale throat, and banded tail. They are usually solitary and go out of their way to harass any other raptor that may be occupying its airspace. Merlins are not buffeted by the wind like kestrels.
American Kestrel – This is the smallest and most abundant falcon in North America. However, the American kestrel has suffered a population decline in recent decades, even after the “DDT era.” One explanation is that there has been an increase in Cooper’s hawks, which prey on kestrels, since the 1970s. Also, in the northeast, much of the farmland where the kestrels hunt has been reforested or developed, so the continued decline may be due to habitat loss. This species is able to hover in the air and drop on its prey, which usually consists of large insects, reptiles, small mammals, and occasionally birds.
Tips for in-flight identification: A small falcon with long, pointed wings, its underside appears very pale. The distinctive mustache and sideburn markings may be visible in flight. This is one of the only raptors that exhibit different plumages for the sexes. Males are the most colorful, with a reddish back and tail and blue-gray wings. The females are rusty all over, with a streaked underside and fine barring on the tail. Kestrels often migrate in small flocks of a handful of birds. Their flight often appears accipiter-like, since they have fluttering flaps, but also glide considerably more than the other falcons.
September 12, 2006. We’ve had large numbers of raptors come through in the last few days! Many days this week had totals in the hundreds, with 295 migrants on September 10 the highest total to date. Traditionally, the middle two weeks of September are the peak migration period for this site, and combined with favorable weather conditions, we have started the week off with strong numbers.
How do birds decide when to migrate? It is probably related to changes in temperature and daylight. In the fall, as the days get shorter and cooler, migrating species get antsy. These external cues cause premigratory restlessness and birds become extremely active and may be unable to sleep. They focus this extra energy toward eating and building up the fuel supply they will need for the trek.
Favorable wind and weather conditions also dictate the timing of a raptor’s migration. Sunny weather is essential. As the sun heats the earth, different surfaces (such as parking lots, granite mountain tops, forested valleys, etc.) heat unevenly. A difference of only one degree Celsius in an area is enough to create a thermal, a warm column of rising air. Many raptors, especially the buteos, have wings that allow them to take advantage of thermals. They will soar around in a thermal, rising in the air until the thermal starts to cool off. The raptors then simply glide to the next thermal. In this manner, they can migrate hundreds and thousands of miles with very little effort. Additionally, if they have a north wind at their backs to help push them south, the trip becomes even easier. Thus, sunny days with a good north wind, such as we have had recently, are when we see the most raptors migrating through.
Featured raptors of the week:
Broad-Winged Hawk – Broad-winged hawks tend to form huge kettles (groups) when migrating. Because these hawks are adapted to take advantage of thermals, one hawk that finds a good thermal is quickly joined by others. At southern HawkWatch sites, such as in Texas and Mexico, it is common to see thousands of broad-winged hawks in a day. Here at Acadia, kettles of 40-50 are the maximum number encountered last year. Broad-winged hawks migrate all the way to South America, following the coastline the entire way. Like most raptors, they are unwilling to fly over the ocean where there are no thermals. They migrate west for a while, from the coast of Florida to Texas (bypassing the Caribbean) and follow the Central American coastline to their destination.
Tips for in-flight identification: Underwings have a dark border; adults have a wide white tail band. They tend to soar in tight circles.
Red-Tailed Hawk – The raspy scream of this raptor is infamous. Film-makers often use the distinctive scream of the red-tailed hawk anytime they need a hawk vocalization—no matter what species they are actually portraying. In contrast to broad-winged hawks, which have one of the longest migrations of any of the raptors, red-tailed hawks may migrate the shortest distance. Red-tailed hawks from eastern Canada and Maine may only go as far as southern New England or the Mid-Atlantic States for the winter.
Tips for in-flight identification: Dark patch on leading edge of wing, may have a dark belly band. Wing-tips tend to curve upward in flight.
September 5, 2006. In just the first two weeks of our hawk-watching season we have seen about 400 migrating raptors! The most common species thus far is the sharp-shinned hawk. Other common species include red-tailed hawks, broad-winged hawks, northern harriers, osprey, and our smallest falcon, the American kestrel.
We are often asked about the difference between a hawk and a falcon. The term “hawk” is often used to describe any diurnal bird of prey, excluding eagles, but especially the buteo and accipiter genera of raptors. Buteos may be considered the quintessential hawk, characterized by broad wings and relatively short tails. They are the real soaring birds, often seen wheeling in the sky, riding thermals, and scouting for prey. Broad-winged and red-tailed hawks are the most commonly seen buteos in this area. Rarely, a red-shouldered or rough-legged hawk may migrate through. Accipiters tend to be woodland hawks and are notoriously difficult to identify in the field. With short, rounded wings, and long, rudder-like tails, they are able to zip in and around trees after their fleeing prey, although they sometimes soar like buteos as well. Sharp-shinned, Cooper’s, and northern goshawks are accipiters that frequently pass through here; sharp-shinned hawks are by far the most numerous. Less closely related to buteos and accipiters, falcons are placed in their own family. With long, pointed wings, these raptors are built for speed. Three species of falcons regularly migrate past the coast of Maine: peregrine falcons, merlins, and American kestrels.
Ospreys are placed in a separate subfamily from the buteos and accipiters. The other common migrants that we observe, bald eagles and Northern harriers, are in the same subfamily as the accipiters and buteos, but are categorized as distinct genera because of their unique features. Turkey vultures are distantly related to the diurnal birds of prey.
Featured raptors of the week:
Sharp-Shinned Hawk – In most birds of prey the females are larger than the males (known as reverse sexual dimorphism). However, the sharp-shinned hawk is one of the most dimorphic species, with females nearly twice the size of males. The “sharpie” often migrates past our site, with an average of 950 seen each season.
Tips for in-flight identification: Discerning sharp-shinned hawks from Cooper’s hawks is a constant source of frustration in the field. Experienced ornithologists often disagree with each other when faced with a fleeting glimpse of one of these accipiters. A commonly-used clue is the speed of the wing-beats. Often described as “flappity-flappity-glide,” the sharp-shinned hawk has quick wing-beats that are almost too fast to count. This relatively small bird may also seem to get “knocked around” a bit in the wind.
Cooper’s Hawk – A recent study found that 23% of Cooper’s hawks examined had healed bone fractures in the chest. Darting through the woods at high speed is a dangerous way to make a living! Cooper’s do not bite their prey to kill it like falcons; they squeeze prey to death with their sharp talons, or sometimes drown their prey.
Tips for in-flight identification: Larger than the “sharpie,” the Cooper’s hawk appears to have more stable flight and slightly slower wing-beats—more of a “flap-flap-glide” pattern to its flight. Sometimes it appears to have a rounded tail, in contrast to the sharp-shinned’s more squared-off tail. It has a wider terminal white tail band than the sharp-shinned hawk. In flight, the Cooper’s hawk appears to have a straight leading edge to its wings, with the head extending well beyond the wrists. The sharp-shinned appears more hunched, tending to hold its wings more forward so its head does not extend much past the wrists. Truly, time and experience in the field is the best way to successfully identify birds in this genus.
August 29, 2006. Welcome to this year’s first edition of Riding the Winds and HawkWatch 2006! Since 1995, Acadia rangers, volunteers, and visitors have helped count and identify migrating raptors. These data are entered into a national database of counts from HawkWatch sites around the country. Monitoring the numbers of raptors moving through each year allow researchers to identify changes in population levels and detect population declines early enough to take action before a species becomes endangered. The 2006 HawkWatch season on Cadillac Mountain runs from Tuesday, August 22, until October 11. Riding the Winds will provide a weekly update on the HawkWatch season and general information relating to raptor migration, as well as commonly seen migrants, natural history information, and tips for identifying them in flight. Be sure to stop in at the HawkWatch site (near the summit of Cadillac Mountain, about 200 yards down the North Ridge Trail) every day from 9 a.m. to 2 p.m., weather permitting, for a first-hand look at these exciting birds.
Many visitors are surprised that raptors migrate. Although a lot of us northerners would like to escape the snowy, cold winter, raptors do not migrate because of the drop in temperature. Consider what you own to keep warm; down jackets and down comforters are filled with bird feathers. Hence, birds are generally covered in very warm “jackets” and could survive the winter well if it were simply a matter of staying warm. Instead, birds need to migrate due to the lack of food in the north during the winter months. Many of these raptors are preying on migrating bird species (who themselves migrate because their insect prey or flower nectar can only be found in southern latitudes during the winter), rodents, which will be hibernating in the frozen north, or insects. Therefore, the raptors follow their food sources to survive the winter.
Featured raptors of the week:
Bald Eagle – This is probably our most charismatic bird and one that many visitors hope to see. A resident population around Mount Desert Island and in Frenchman Bay stays here year-round. Plentiful gulls and other seabirds sustain them throughout the winter. Also, many of the eagles that spent the summer farther inland will migrate only to the coast for the winter, since the fresh water they were feeding in previously will freeze. However, we do see some bald eagles that we consider to be migrating south. It is impossible to say with certainty; however we generally consider eagles to be migrating if they are seen in a direct flight pattern in a southerly direction, as opposed to lazy circling or meandering flight. This raptor is no longer considered endangered federally, but was de-listed to threatened status in 1995. It is also considered threatened in Maine; however with a strong population of more than 385 pairs in the state it may soon be taken off the list entirely.
Tips for in-flight identification: The size of the bald eagle is one of the best keys for identification, especially of juveniles. This is the largest bird in the area, and it often holds its wings very flat when soaring. Adults are unmistakable with dark bodies and a bright white head and tail; however, juveniles are mostly all dark with variable white mottling.
Turkey Vulture – The turkey vulture is generally not considered a true raptor, but often gets lumped together with other birds of prey. This bird preys only on carrion and does not kill for itself. Furthermore, it is genetically more closely related to the storks, penguins, and herons than to other raptors (recent molecular studies have led the American Ornithologists Union to reclassify turkey vultures and place them in the order Ciconiiformes, while the true diurnal raptors are in a separate order). Like other vultures, its head is bare of feathers so that when it is devouring carcasses it doesn’t get caked with blood. This species also has an interesting method of cooling itself via excreting on its legs. Like the bald eagle, Mount Desert Island has many local turkey vultures. Although they will eventually all migrate for the winter, we continually have to judge their behavior to determine whether or not each one we see is migrating through.
Tips for in-flight identification: Large, dark bird with a two-toned underside, tail longer than head, holds wings in strong v-shape or dihedral, tippy flight pattern.