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HawkWatch Update Archive - 2007

Soaring Turkey Vulture

Welcome to the HawkWatch update archive for 2007. Go directly to a particular issue of Riding the Winds by clicking on a date below

October 10 | October 2 | September 26 | September 19 | September 12 | September 5 | August 29

 

October 10, 2007. HawkWatch officially ends today. We are all very sad that our season is over, but we have had a fantastic year! As of October 8, we had broken our record for the highest number of migrating hawks in a season (3,652), up quite a ways from our average of 2,460. With such high numbers, we managed to break a few other records, too. We broke the record for the highest number of northern harriers seen in a day (21), as well as in a season (158), up from our yearly average of 78. We had our highest yearly number of sharp-shinned hawks (1,514—average is 960) and the second highest yearly number of American kestrels (1,030—average is 695). We also had our second highest yearly number of osprey (206—average is 146), and we tied the record for the highest number of peregrine falcons seen in a day (3). So, what do we do with all these impressive numbers, and what do they mean?

Actually, we cannot really draw any conclusions from our data alone; there are too just too many variables. Birds that we miss could be scooting around either side of Cadillac Mountain, or they could be flying several miles inland, where they can see the coastline but we cannot see them. Perhaps higher numbers indicate that more raptors were born this year, or maybe they just took the scenic route and got pushed closer to the coast by the winds. Scientists must look at all the hawk watch sites across the country and over a long period of time to really get the big picture.

To get this picture, we enter in every bird we see each day into www.hawkcount.org, a database analyzed by the Hawk Migration Association of North America (HMANA). They can look at all the data entered by each hawk watch site in the country and from there estimate how our raptor populations are doing. We are happy to say that because of this data we know that our birds of prey are doing very well, and most species are still increasing in number. The only bird that is in decline is the American kestrel. Scientists are still trying to figure out what exactly is going on, but they have narrowed it down to several factors. One is habitat loss; kestrels like open fields and edges, and as our land succeeds back to forests they are losing that habitat. West Nile Virus has also been found in kestrels, as they like to eat dragonflies and other little bugs. They also may be declining due to competition with the bigger and more numerous Cooper’s hawks, which have been known to prey upon the tiny kestrel. Another factor may be the lingering effects of DDT or another pesticide that we are not yet aware of. It is because of hawk watches that we were able to identify this problem early and hopefully solve it before their decline spirals out of our control.

Imagine if we had hawk watches throughout history; just going back 100 years we would have been able to trace our influence on the bird of prey populations. We would have witnessed their decline at beginning of the century when egg collecting and shooting drove their numbers down. We could have caught and perhaps prevented their dramatic decline during the DDT era. We would have been able to see their incredible comeback due to the Endangered Species Act and education about birds of prey. In that history, we could see how far we have come in our relationship with raptors, when once they were perceived as terrible threats that must be eradicated, to symbols of freedom and struggles overcome. But their struggles are not over, nor will they ever be. Every day is a struggle to survive, whether we help or hinder them. We hope all the birds of prey we saw this season survive and return for the next, and hopefully you will too! We hope to see you and the birds the same time next year, whenever the north wind blows…

-Sarah Stio

 

October 2, 2007. HawkWatch continues to see migrating hawks pass overhead, despite the fact that we are past our peak. This weekend the north winds brought a total of 271 raptors on Saturday and 274 on Sunday, and most flew extremely close by! Below are the quick profiles of some of these migrants who deserve to be recognized before our HawkWatch season is up.

If you have ever seen a hawk snatch a little bird from your birdfeeder, you have probably seen a sharp-shinned hawk. They are the most abundant species we see at our HawkWatch, averaging around 960 birds a year. Adults are brown above and rust colored below, while the juveniles have brown barring below. The birds we see will spend the winter anywhere between Massachusetts and Central America.

The Cooper’s hawk is a slightly larger accipiter, but otherwise almost identical to a sharp-shinned. One way to tell the difference is their tail: the Cooper’s is rounded, and the sharp-shinned’s is squared off. Both have a “flap-flap-glide” flight pattern, but the sharp-shinned has quicker wing beats. The Cooper’s hawk has a little bit slower, more labored wing beats. We see on average 34 Cooper’s hawks, each heading to the Gulf of Mexico or Central America for the winter.

The northern goshawk is a treat to see during HawkWatch, as we only average about six of these birds a year. The adult birds are a beautiful gray color with piercing red eyes, but we tend to see the juveniles, who are all brown. They fall into the accipiter family, but are much larger and chunkier than the sharp-shinned or Cooper’s hawks. These birds are a late migrant, heading to winter in the woods south of the Great Lakes.

When most people think of hawks, they think of the red-tailed hawk. A widespread, large buteo with its signature red tail, they are often seen perched on a telephone pole or soaring high in the sky, looking for their next meal. Another late migrant, we average around 48 birds in a year. Most of these birds will just go a few states south, where the winters are a little milder and the hunting a little better.

Broad-winged hawks are your typical buteo, rarely flapping in flight and often seen soaring in giant kettles. These birds have a brown back and a dark outline on the bottom and at the tips of their white underwings. They will journey all the way down to the Amazon for the winter, where their favorite meal of snakes and frogs will be abundant!

The fastest bird in the world, the peregrine falcon, is another rare bird to spot at our HawkWatch, with only about 13 seen in a year. The largest and most powerful of our three falcons, their dark mustache and white chest gives them away. These birds of prey, including our four resident pairs, can journey all the way down to South or Central America for the winter.

The merlin is another fun bird to see during HawkWatch. Smaller than the peregrine but larger than the American kestrel, this is a darker falcon above and below, with a very deliberate and direct flight. They are known for harassing other raptors on their journey down south, where they winter anywhere from New Jersey to Central America.

The American kestrel, our smallest bird of prey, is the second most abundant species we see at our HawkWatch, with about 695 birds a year. The males boast bright blue wings and a red back, while the females are a buff brown. They tend to migrate with a buddy or two, and get tossed around in the winds. In the winter, they will head to Florida or Central America, where the big bugs and dragonflies they crave are plentiful.

With only a week of HawkWatch left, time is running out to see all of these magnificent raptors on their migration south! So hurry and join us on top of Cadillac, 200 yards down the north ridge trail any time between 9 a.m. and 2 p.m. (weather permitting).

-Sarah Stio

 
Raptor Silhouettes (Osprey and Northern Harrier)

Osprey (top) and northern harrier (bottom) silhouettes

September 26, 2007. For mid-September, it has been a slow hawk-watching week. We were stuck in a southerly weather pattern for most of the week, and although these winds brought us nice warm weather, they do not bring migrating raptors. The winds shifted to the northwest on Sunday and Monday, but we did not see the hundreds of birds we were hoping for. On Monday however, the 183 birds we did see gave us amazing views! We also saw our first northern goshawk of the season and broke our record for the number of northern harriers seen in one day—19. Hopefully, we will have a few more exciting north wind days before our HawkWatch wraps up. In the meantime, we will continue to sharpen our identification skills and look at our last two categories of raptors.

The ospreys are in a league of their own, as they are the only raptor specially built to catch exclusively fish. They are often seen hovering over the water, searching for a meal. Once a fish is spotted, they dive feet first up to a meter deep in the water, then immediately spread their oiled, water-proof wings and quickly get out, for the osprey cannot swim. They almost always emerge with a fish in their talons. Bald eagles have even been known to steal fish from them, as osprey are the better fishermen. We have approximately a dozen pairs nesting around Mt. Desert Island, but they leave their summer home every fall for their winter home in southern Florida and the Caribbean. Ospreys are relatively easy to identify as they migrate through, as they are the only large raptor with “M” shaped, droopy wings. The only other bird to take that shape would be a gull, but an osprey is considerably larger with its 5-foot wingspan. We get quite a few ospreys soaring over Cadillac Mountain, giving us great looks of their white belly, dark underwing patches, and dark eye stripe.

Northern harriers, once known as the marsh hawk, are in the last unique family of birds of prey. They are relatively easy to identify, as they have a white patch on their rump, a feature no other bird has. They will hold their 5foot long wings in a slight dihedral, similar to that of a turkey vulture. The females and juveniles are all brown, while the males are a beautiful gray color. These “gray ghosts” are a rare treat to see during our HawkWatch. If they get close enough, you may be able to make out their owl-shaped face, the only diurnal raptor to have this feature. The feather disc serves the same purpose as it does with the owls, to capture sound, which they rely heavily on to catch small birds and mammals over the marsh. Some harriers we see pass over us are on their way to the southern United States, the Caribbean, or South or Central America.

We still have a few more weeks of our official HawkWatch left, so hurry up to Cadillac before we see our last harrier or osprey—would not want all this new knowledge to go to waste! We will be 200 yards down the North Ridge Trail between 9 a.m. and 2 p.m. every day (weather permitting), so join us before the rangers and the birds migrate south for the winter.

-Sarah Stio

 
Raptor Silhouettes

Bald eagle (top) and turkey vulture (bottom) silhouettes

September 19, 2007. As September rolls on, we approach the peak of our hawkwatching season. This past week brought an unexpected north wind on Thursday, bringing with it 303 birds. Sunday’s winds brought 305 birds, and Monday’s brought 286! True, these are good numbers, but we still are hoping to see some 400-500 bird days! To prepare for such busy days, we must continue to sharpen our hawk identification skills. Last week introduced the three main families, the buteos, accipiters, and falcons. This week we will look at some birds of prey that are in their own unique categories.

First of course is our bald eagle, the bird that everyone must see! We have about 12 pairs nesting in and around Frenchman Bay, so your dreams of seeing bald eagles have a good chance of coming true. Identifying them is not difficult; with a wingspan of 6-7 feet, they are the biggest and one of the darkest birds in our skies. Of course if they are close enough you can also identify them by their white head and tail. However, a juvenile bald eagle will be completely dark brown from head to talon. They will slowly gain their regal adult plumage by their fourth or fifth year. The best way to identify a bald eagle, as with other birds, is their flight style. They will hold their wings as solid and as flat as a board, and rarely will they flap. The bald eagle is well built for soaring high in the sky, as that is how they spot their food. Not to shatter anyone’s view of the majestic bald eagle, but they are scavengers and opportunists. They will spend their days soaring around looking for the easiest meal, be it a dead seal or a dying duck. We usually see at least one or two of our local bald eagles soaring and searching during our HawkWatch. They do not tend to migrate from our area in the winter, as the ocean never freezes and there is an abundant food supply. We do, however, see bald eagles migrating from farther north of us, as well as young birds who decide to wander for their first couple of years.

Another large, dark bird often seen soaring in the sky is the turkey vulture. True, they are not real birds of prey, but they soar as gracefully as any buteo. They are often seen riding in thermals and kettles with other birds of prey, so they are lumped into their category. While the turkey vulture has the same sharp, raptor-like beak to tear into meat, it does not have the sharp claws with which to kill it. Someone else does the dirty work; the turkey vulture simply cleans it up. We have about a dozen turkey vultures living on the island, and each day we will see them soaring around and around the mountain, looking for dead animals. The best way to identify the turkey vulture is, again, their flight style. They will hold their wings in a dihedral, or a V-shape, and they will teeter in the winds (think: teetering turkey “V”ulture). If you are close enough you can also see their two-toned black and gray wings, as well as their red, featherless head. They will eventually migrate in late September or October, going only a few states south where the weather and road kill are better. Occasionally, we will see some that are migrating from the north.

There are still two other unique birds of prey that we see soaring over Cadillac Mountain, but that will have to wait until next week. Or better yet, join us at HawkWatch anytime between 9 a.m. and 2 p.m. (weather permitting) to see and learn about them for yourself!

-Sarah Stio

 
Bird Silhouette

Buteo (top), accipiter (middle), and falcon (bottom) silhouettes

September 12, 2007. If you picked the right day to be hawkwatching at Acadia National Park last week, you were rewarded with a stream of migrating raptors carried in by the north winds. On Wednesday, September 5, 458 raptors soared over Cadillac Mountain in eight hours! This is an incredible number for this time of year; usually we do not see that many until mid-September when our hawkwatching season peaks. Why we saw such a high number of birds this early is unknown. We were afraid that we used up our seasonal hawk quota in one day! But on Sunday when we had another north wind, we saw 316 hawks pass in five hours, so we know they are still coming.

When there are so many hawks zipping over and all around you, your hawk identification skills are really put to the test! To make things easier, raptors are grouped into families, or categories, which are based on genetics, the habitat and food they prefer, their physical characteristics, and their flight patterns. The best way to identify these hawks in flight is to start with these basic families, learn their basic shapes and flight patterns, and then go from there.

The first and most familiar hawk family is the buteos. They consist of red-tailed hawks, broad-winged hawks, and red-shouldered hawks, to name a few. These birds are masters of the winds. With their long, broad wings and short, often fanned tails, they can soar thousands and thousands of feet above us without flapping once. In migration, they are most often seen soaring in thermals and creating kettles. Their ability to soar so well and so high make them well adapted for hunting in open fields, where they can spot small animals thousands of feet below.

Another family of raptors is the accipiters, which consists of the sharp-shinned hawk, Cooper’s hawk, and northern goshawk. These hawks are built for quickly maneuvering through thick forests in search of prey. Their wings are short and rounded and their tails long and narrow. These adaptations allow them to quickly fly through the trees and grab little birds. In migration they often use the updrafts created by landforms, such as Cadillac, to carry them up and over the mountain.

The third family of raptors is the falcons, such as the merlin, peregrine falcon, and American kestrel. These birds are built for speed. They are a smaller bird with long, pointed wings and a long to medium tail. These features make them excellent at snatching birds or other animals while in flight. When migrating, they ignore thermals and updrafts and cut right through the air with their powerful wings.

By knowing these three basic families, you can start to narrow down the birds you see and better identify them. There are still a few more families who are off in their own categories, which we will look at next week. In the meantime, come up to HawkWatch on Cadillac Mountain anytime between 9 a.m. and 2 p.m. (weather permitting) and put your new hawk identification knowledge to the test!

-Sarah Stio

 
Thermal Diagrams

September 5, 2007. The second week of HawkWatch started off slow, but ended with a bang. Friday night saw the passage of a cold front, bringing with it strong north winds and sunny skies. These are the key ingredients for raptor migration. In seven hours on Saturday, we saw a total of 197 migrating birds, 123 of which were American kestrels! The next day saw 192 raptors in seven hours, 133 of them sharp-shinned hawks. We most likely would have had more on the second day if it was not for a shift in the winds from north to southwest in the afternoon. These birds are picky; they want north winds and north winds only.

As hawk-watchers, we often wish birds would fly every day in every wind direction, but for the hawks it is a matter of life and death. Since these birds are flying from the north to the south, they only want to fly when the winds are at their backs. If they were to fly against the wind, they would have to work much harder and waste a large amount of energy, perhaps so much that they would not make it to their southern destinations. Flying is already an energetically expensive activity, and migration means they are flying great distances in a day. So why not take a free ride from the north winds and make it easier?

Sun also makes life easier for our migrating raptors. As the sun heats up the rocks and parking lots, warm air begins to rise up in pockets called thermals. Birds can detect these thermals and jump into them, taking a free ride up into the sky. As these thermals get higher and higher, they eventually dissipate and spread out, at which point the birds will look for another rising thermal to jump into. Broad-winged hawks and turkey vultures are specially designed for exploiting these thermals. During migration, they can cover great distances with ease simply by gliding from thermal to thermal.

Many birds will often jump into the same thermal together, creating what is known as a kettle. Kettles are made up of sometimes hundreds or even thousands of birds, soaring around and around and up and up into the sky, much like water boiling and bubbling in a kettle. These birds can soar thousands of feet in these kettling thermals, much higher than the range of even the best binoculars. We can only wonder how many birds go unseen as they pass 3,000 feet above our heads.

Hawks will also utilize wind updrafts created by landforms, such as a mountain. We see a good deal of this slope soaring on top of Cadillac Mountain, as the wind carries them up the mountain and literally right over our heads! Sharp-shinned hawks and Cooper’s hawks are well built for this slope soaring, possibly one reason why we see more sharp-shinned hawks than any other bird at our HawkWatch site.

But what makes a sharp-shinned hawk better at slope soaring than an American kestrel, or a broad-winged hawk better at kettling than a Cooper’s? You will just have to wait until next week’s exciting edition of ‘Riding the Winds’ for the answer. Better yet, come on up to Cadillac Mountain from 9 a.m. to 2 p.m. (weather permitting) and see it for yourself!

-Sarah Stio

 

August 29, 2007. As summer winds to its inevitable end, we turn our eyes to the skies in search of migrating birds of prey as HawkWatch 2007 kicks into gear. We have already seen 50+ migrating birds of prey, and we are only at the beginning of our season! But why are these birds migrating? Where are they going? How do they get there? This first edition of Riding the Winds hopes to answer these questions for those that want to know just a little bit more about the mystery of migration.

As the days get shorter and cooler, birds of prey, just like our summer visitors, leave the North Country to winter in the warmer latitudes. Some just go to the southern United States, while others journey all the way to Central and South America. There are several theories as to why this occurs. The obvious is that they are following their food source and escaping the colder climate of the north. Less obvious is the theory that these birds evolved in the southern latitudes, and in order to avoid competition for food resources and nesting locations, they migrated north to breed and raise young for the summer.

Just how birds migrate is still a bit of a mystery of science. Prey abundance and temperature most likely play a role in deciding when it is time to migrate, but the most important factor is the photoperiod, or the length of daylight hours. As summer progresses, the amount of daylight decreases, triggering hormones that tell the birds it is time to prepare for their journey. They start to pack on the pounds (or in their case “ounces”) to use as fat reserves for their flight, and they become antsy and restless. Studies have shown that songbirds, which migrate at night, become restless in the dark and hop in a southerly direction.

How these birds find their way to their wintering grounds is another mystery. Studies show that they can use external cues such as the position of the sun and the stars, and some even use their heads as a mini compass and follow magnetic fields. Their traveling route and destination may also be programmed into their genes. In addition, they will use landmarks so that they do not get lost along the way, such as coastlines and mountain ridges. The birds that pass through Maine are following the Atlantic Coast, which acts as their highway in the sky. It is along these landmarks, such as the Atlantic Coast, where great concentrations of raptors can be seen, such as on top of Cadillac Mountain in Acadia National Park!

Why they do it and however they do it, you can guarantee that when that north wind blows in the fall, the raptors will be migrating. So join us for this amazing sight on top of Cadillac Mountain from 9 a.m.to 2 p.m. (weather permitting), just 200 yards down the North Ridge Trail. Bring your binoculars (don’t worry, we have some if you don’t), your patience, and your sense of wonder as you watch these birds make their incredible journey south.

-Sarah Stio

Did You Know?

CCC members take a break from their work to admire the view along the ocean.

The Civilian Conservation Corps performed important work in Acadia National Park, including clearing brush, setting stones, and constructing Seawall Campground. Today park headquarters is located in the former CCC camp.