The Great Fall Raptor Migration

Over a month ago, I was able to spend a weekend along the shores of Lake Superior. The purpose of the trip? To see migrating raptors of course! One the best places to see the massive raptor migration in the fall is at the Hawk Ridge Nature Reserve in Duluth, MN. It's located on bluff overlooking the city and the lake.

According to the Hawk Ridge Bird Observatory, 100,000 raptors are seen on average flying over Hawk Ridge each year. And it is not just raptors that pass through the area - many songbirds can be seen migrating along the shoreline as well. In fact, the September weekend I was there a Lark sparrow had found its way to Hawk Ridge. This a rare sighting for the Duluth area! The little sparrow was hanging out on the ground feeding on seeds very close to the main area where hawks were being released. There were a few times the bird eating hawks spotted the little sparrow and took aim at it! It was still there when I left on Sunday - alive and well!

So why is this particular area of Minnesota such a hotspot for migrating birds in the fall? It all has to do with geography! Duluth is surrounded by ridges and bluffs to the west and the open water of Lake Superior to the east. Birds are not so willing to fly over a large body of water such as the lake, so they follow the ridgeline southwest along the North Shore. They end up getting funneled down to the narrowest tip of Lake Superior in Duluth and we end up with large concentrations of birds riding thermals overhead.

Those thermals are created when the sun heats the bluffs and ridges and the warm air rises up. The birds ride these columns of warm air to help them gain altitude. They don't have to flap their wings much so they conserve their energy, which they will need for their long flights to the their winter grounds south. Because they depend on the warming of the earth and these thermals, the birds will migrate along the shoreline when the conditions are right. Check for cold fronts moving from the northwest. The best hawk watching can be seen just before the cold front passes until a few days afterwards.

The kinds of hawks you will see at Hawk Ridge depends on the time you visit. The migrations begin in mid-August and go through the end of November. The earlier migrators will be the songbirds and the smaller hawks. September sees the greatest number of migrating birds with over 100,000 broad-winged hawks, over 1,500 sharp-shinned hawks, over 800 turkey vultures, over 750 kestrals and over 100 red-tailed hawks. In October more hawks come through - bald eagles, northern goshawks, and northern harriers are added to the mix. And as the season winds down more of the bigger birds come through including rough-legged hawks and golden eagles.

My visit was in mid-September was during their hawk festival. The majority of the birds seen that day were sharp-shinned and broad-winged hawks. There are bird counters who spend their days counting the number of birds seen. There are also reseachers manning the mist nets to band the caught birds. And there are naturalists on hand every weekend in September and October to lead programs and give information on the birds seen and released. Here's a sample of the number of birds seen on a Saturday:

All of these birds mentioned are in the same Family, but are grouped into separate subfamilies based on their characterisitics. A few things they all have in common are that they are diurnal (up in the day and therefore migrate during the day) and they have excellent eyesight. They all have the classic raptor features of hooked beaks and talons for grasping and tearing flesh off the bones. They are meat eaters and some have a varied a diet eating everything from insects to mammals to carrion while others are very specific (the snail kite eats only snails!).

Here's a run down of the subfamilies:

1. Kites - These birds are found south of Minnesota so they are not seen migrating through here. They are smaller birds and eat mainly insects and snails. They do live south along the Mississippi River so there is some Minnesota connection. Let's keep our river clean for those living downstream from us!

2. Accipiters -These are the "bird hawks" and they, of course, eat birds! They include the sharp-shinned hawk, Cooper's hawk, and northern goshawk. They have long, slender legs and a long tail perfect for flying through the trees of a forest. These birds look different during their first year than they do as adults. Their markings and eye color are different - vertical brown stripes and yellow eyes in the 1st year and horzontal brown stripes and red eyes as an adult. Here's a photo of three first-year sharp-shinned hawks about to be released:

3. Harriers - there's only one bird in this grouping. The Northern harrier is also called the marsh hawk. The males are grey and the females are brown.



4. Buteos - these are the stocky hawks commonly seen perching along roadsides and soaring overhead looking for prey in fields. They include the red-tailed hawk, the Swainson's hawk, the rough-legged hawk, the broad-winged hawk and more. The Sunday I visited Hawk Ridge there was a red-tailed hawk released. Here's a bit of information on the hawk and some good shots of the wings. You'll get a good idea of size difference between a buteo and an accipiter too.

The red-tailed was released that day as well. Here is a brief clip of the bird being released:

5. Eagles - this group has one of the most recognizable birds in North America, the bald eagle. It also includes the golden eagle. These are mainly fish eating birds and they are kind of bulky birds. Here's the not so well known golden eagle:

6. Ospreys - these birds are in their own group! They eat only fish and dive head and feet first into the water to catch their prey. They can be seen along rivers including the Mississippi River. There is a pair of osprey that return to the Coon Rapids Dam on the Brooklyn Park side every year. They make their nest on the utility pole and hunt all season long in the river. Here's a photo of their nest from a few seasons ago:

Of course, there are other birds to be seen at Hawk Ridge. We did see several turkey vultures over the weekend. We also were fortunate enough to see a kestral released. Kestrals are in the falcon family along with prairie falcons, peregrine falcons, and gyrfalcons. Male kestrals have blue-grey wings while the females are brown. These birds are fantastic! They eat insects including dragonflies and they time their migration with the migration of the darners! (See my previous post on green darners!) They eat these large flying insects on the wing! How fantastic would it be to see a kestral with a green darner in it's beak freshly snapped out of the air!!

Here's the male kestral showing off his pretty coloring:




He was released by a little girl who adopted him. She said she waited until a kestral was banded because she thinks they are so pretty! Good choice!!! Here's the kestral being released:

It is not just the coloration that is different between males and females for kestrals and other raptors. Many species of raptor show "reverse sexual size dimorphism" which is a fancy way of saying the girls are bigger than the boys. Why? I don't think there is one answer to why the females are larger than the males. It could be that the females need to be larger in order to produce and incubate the large eggs that they lay. Also the females are the ones who are sitting on the eggs and protecting the nest, so being larger would help to fight off potential egg or chick thieves. The larger females can also hunt for larger prey than the males so therefore they each exploit a different food source and fill different niche. That decreases competion for the same foods. The groups of birds that show the most size differences are the smaller bird eating raptors like accipiters and falcons. Carrion eaters like vultures and buteos do not show much size variation.

So the next time you are driving along the road and see a large, bulky bird sitting on top of the street light impress your friends by shouting out, "There's a buteo!" If you are in the Duluth area in the fall, head on up to Hawk Ridge and bring your binoculars. The naturalist staff, volunteers, and general public are super friendly and very helpful. It's a great way to spend a portion of your day.

There are plenty of places throughout North America to view raptor migrations, so don't fret if you don't live near Duluth, MN! The Hawk Migration Association of North America has information, articles, and more on it's website. You can also click on your state or province to find raptor viewing locations near you.

The Last Monarch....

Yesterday the last monarch butterfly of the Garden season emerged. It wasn't the best day to emerge as a new butterfly - cool, windy, rainy, and in the evening more rain and wind and even a tornado watch. Needless to say, I left the new metamorphosed creature in the enclosure in the Martha Crone Visitor Shelter overnight.

This morning I came in to work and saw the butterfly still hanging from it's chrysalis. It was in the 50s this morning which is a bit too chilly for an insect to be moving about with ease. So I carefully placed the butterfly in a bug box and placed it on the table closest to the fireplace. I just wanted it to warm up after a chilly night in the Shelter.

Monarchs are truly amazing. Well, all butterflies are really. Think about this: they start their lives as tiny caterpillars hatched out of a tiny white egg. Their first meal? Their egg! What next? The milkweed leaves the egg was deposited on. They eat and eat and grow and grow shedding their skin several times. The milkweed leaves they eat are slightly toxic but they are immune. Anything that eats them makes the predator sick (birds throw up if they eat a monarch). Predators learn not to eat these guys.

Then something amazing happens! They begin to wander - go for "walkies". They find a leaf and hang themselves upside down in the "J" shape. They molt their skin one more time and form a delicate green chysalis with tiny gold dots around the edge. Beautiful!!! And they remain in that form for 10 to 14 days. During that time, they completely rearrange themselves! The caterpillar is no longer a caterpillar. It takes its caterpillar parts and assembles a completely new creature! After 10 to 14 days, the green chysalis becomes clear and one can see that inside is something that is black and orange. A butterfly is inside!!! Suddenly the chrysalis breaks open and this incredible new being emerges and spreads its wings for the time! Truly amazing!

Check out this video I took a while ago of a monarch caterpillar in J-shape and a monarch butterfly emerging!



Around noon today I brought the newly emerged butterfly up to the prairie. It was still overcast and still a little cool. I was hoping it would be warmer up there on the hill and that the little insect would quickly find the flowers and food it needed to survive. I was worried about this one. It was lathargic and still, only flapping it wings every once in a while. I opened the container and let the butterfly crawl onto my warm finger. It stayed there, clinging to my fingertip. It opened and closed its wings a few times and I was hopeful it would take off. It didn't. Soon I moved over to the edge of the clearing under the oak tree and placed the butterfly on a flower. It reluctantly and awkwardly left my finger and gripped the tiny white flowers. Hmmm...



I was concerned, yes, but understood. The weather has changed dramatically in the last two weeks. At the end of August it was hot, humid and sunny. Suddenly September arrived and so did autumn. And this week the temperatures have not gotten above 70 and we shouldn't expect to see those days again this year. One of the factors that trigger migration not only for monarch butterflies but for birds and other migrators (including dragonflies!) is temperature. Another is the length of day. Now as 7pm approaches dusk is upon us and the day is ending. In the morning the sky does not lighten until nearly 7am. Next week is the equinox and then we will begin to have less than 12 hours of daylight until March. And now the blooms of our flowers are nearly all done and the plants are beginning to senesce. Living things see and feel these changes and know that autumn is here and winter is not far behind. The leaves have already begun to change and fall is here in the Twin Cities. It's time for creatures to migrate or stock up on supplies or get ready to hibernate. They know.

If this monarch I released today survives, it will fly to Mexico. MEXICO!! 3,000 miles!!! What an incredible journey! Flying over prairies, lakes, rivers, and deserts to Mexico. Amazing! You can follow their journey by visiting Journey North From this page you can follow not only monarchs but other migrating animals too. Check back in the spring to find out when they will be returning to your state. And then you will get another season to enjoy the monarchs! The monarch who make here in the spring are actually the 3rd or 4th generation from the original butterflies who flew down to Mexico.



So how do they know where to go? They may use the Earth's magnetic fields or the position of the Sun or both or other factors. Who knows? No one really. Once thye arrive in Mexico, they live in the mountains high above sea level. They cluster together for warmth and use the humid air to stay moist. Unfortunately, there is significant habitat loss not only in Mexico but here in the United States as well. Monarchs have fewer places to find food, lay eggs, and overwinter. There are organzations out there doing their part to raise money and awareness to the plight of the monarchs (the Minneapolis Park and Recreation Board has a Monarch Festival in September). And just raising monarch caterpillars is a fun, rewarding way to help the population along. Those little caterpillars will be protected from predators while they are young in your care and hopefully will make it to maturity to lay some eggs and perhaps migrate to Mexico!

I'm not sure if my monarch flew off today. I'd like to think he did. I'd like to think that the little orange and black miracle found some flowers, powered up and took off in a southerly direction. Or at least became nourishing food for a bird...

For more information on monarchs, their migration and more check out: http://www.fs.fed.us/monarchbutterfly/migration/index.shtml

A Windy Day Brings A Garden Visitor...

Last week we turned another calendar page and it seemed as though Mother Nature felt it was time for a change as well. "Bring in autumn!", she seemed to shout! September 1st was a perfect, gorgeous day with pleasant temperatures, low humidity and lots of sunshine. What a pleasure to just be alive after so much heat and humidity in August! But by Friday, the weather turned cooler - tempertures that here in the Twin Cities have not seen since late spring. The air was brisk in the 60s and the wind gusted through the trees. Suddenly the seasons changed from hot, sticky summer to cool, windy autumn. I love autumn, but according to my calendar the equinox is not until September 23rd.

It was cool enough out there in the wind on Friday that I decided to build a fire in the Shelter at the Eloise Butler Wildflower Garden. The wind was tossing the tree tops around like seaweed along the ocean shore. I went about my morning opening the Shelter and filling the bird feeders including the suet feeder in the hopes the pileated woodpecker would return that day. I reached out for the screen door handle to go inside and get some bird seed only to quickly pull my hand back in surprise. There right on the handle was a dragonfly taking shelter from the wind and cold on the porch and probably feeling the heat coming inside. I laughed at the funny noise that came out of me and then gently let the insect crawl onto my finger. I placed it on the porch bench and went inside to grab a plastic terrerium. I decided to bring the dragonfly inside to warm up and get out of the wind.

Upon closer inspection, I discovered my dragonfly friend was a Common Green Darner and a female. These dragonflies are one of the larger ones around and also one of the most common, found all over the United States and southern Canada. These are the ones that are seen along ponds and lakes a few feet about the surface of the water, but they can also be seen farther away from water in the uplands. They are strong fliers (they are good size) and I have seen them on the high cliffs along Lake Superior battling the lakeshore breezes patrolling for mosquitoes. Early autumn is a great time to see green darners inland.

Male green darners are have green thorax (the middle section of the body between the head and abdomen) and a blue abdomen with a black stripe going down the middle. Females also have a green thorax, but their abdomen is a rusty, brick-red color though sometimes it looks violet. Both sexes have large compound eyes that are a dull green color with a bull's-eye pattern on the forehead.









On this chilly, windy day my female darner was looking stunned. I put her gently in the plastic "bug box" and brought her inside. She flitted a few times, but not much. I continued to fill the bird feeders while keeping and eye on her.

Common Green Darners are truly amazing (as are all Odonatas if you ask me!). There are some green darners that will migrate in search of food. We are not talking great distances like the monarch butterfly (the most famous of the migrating insects), but they will still leave their "home" and travel many miles in search of good eats. What do they eat? Thankfully they eat those pesky biting insects (I love watching them patrol!), but they also eat other, smaller dragonflies and some have been seen eating hummingbirds!!

I finished filling the feeders and checked in on my dragonfly friend. She was making an awful lot of noise - flitting about and bumping into the sides and top of her enclosure. I knew I needed to let her go and her warming up was only temporary. But I told myself, if she can fly into Lake Superior shoreline head winds and if she can hunt down a hummingbird for dinner, I think she can handle a windy, cool fall-like day. So I brought the "bug box" out onto the porch of the Shelter and opened the lid carefully. A swirling gust of chilled air rushed down the slopes leading into the bottom of the Garden where the Shelter sits. In a flash, she was sucked out of the container and rode the wind up into the Ohio buckeyes and headed along the ridge where the woodlands meets the prairie in the Garden. I hoped that she would find refuge from the wind and chill somewhere in the conifers that line the woods surrounding the prairie and that she made it through the cool nights to follow.

I'd like to think she did. I'd like to think that she began flying south to a sheltered pond out of the wind. That she deposited her eggs just below the surface of the water so another generation of green darners could patrol the skies eating mosquitoes and biting flies for us.