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.
