Hawks are numerous during the summer; in fact, large numbers will follow a tractor as it works the fields ready to dive to pick up a meal in a small rodent. However, this fall, after our first winter storm, I saw more hawks sitting together, then I have ever seen. I was traveling to the Mountaineer one morning to find a hawk sitting on every fence post for one and a half miles, plus there were many flying or sitting on the ground. I called Fish Wildlife and Park in Great Falls, to find out what was going on. I took photographs of a different kind the best I could. There were four different species of hawks all sitting together; Red-tail hawk, Coopers hawk, Rough-legged hawk, but most of them were Swainson Hawks. Kristina Smucker, Wildlife Biologist,
told me that she thought it was rather rare that different species of raptors would hang out together.
Initially, I had thought there were over 100 hawks. Still, I told her 50-75 for fear she thought I was nuts. However, I discovered from her after she talked to an expert in the field that different hawks would "kettle" up after a winter storm and that over 100 raptors would be an appropriate count. They stayed in the same area for about three days. I noticed most of them went and sat in the fields.
Kristina wrote Kate Atkins, Senior Associate Biologist from Tetra Tech (Portland, Or), who is one of the tops in her field. She wrote, "Yes indeed they can move in huge kettles - and this hanging around in fields together in between flights is textbook Swainson's hawk behavior. During my Cut Bank days, each fall, these birds would group up in an area conveniently located between work and town. My pals and I up there enjoyed the chance to pore over their appearances since they were so kind as to hang out and let us look at them at length. They are quite beautiful. Perhaps not as variable as say Roughies, but still, in a group of 100 or so, there are usually some unique stunners to drink in.
Up in the northern parts of the lower 48, we might see them plunked in a field in the 100s, but as they funnel ever southward towards their South American summer vacation, they can be observed in massive groups. I took a wander through some southern US hawk watch data (the bottom of the funnel) and cherry-picked this standout day from Corpus Christi: on October 8, 2008, that site clocked 14,859 migrant Swainson's hawks in a single day.
They are indeed commonly observed congregating in ag fields in the fall, generally gorging on grasshoppers, which are plentiful at that time and easy to grab in a stubble field. In MT, the harvest happens to coincide with the largest numbers of them being present (adults and young) - they're off territory and grouping up - so these scenes occur particularly in ag fields in MT annually. I do miss that big sky and those endless, unobstructed views."
I researched the four different hawks from a web site Raptors of the rockies.org. The following information is directly from their web site.
"Coopers Hawk Behavior:
Feeds mostly on birds and small mammals. Sits quietly, hidden in tree limbs and leaves, dashes out in quick short flights. Very maneuverable in dense foliage. May fly along fence rows to surprise prey. Very energetic in chasing prey even on foot in the brush and even down burrows. Smaller male tends to catch the smaller more numerous birds close to the nest to feed female and young. Later in nesting female may travel farther to find larger birds. May locate quail by listening for their call.
Nest and eggs: Large stick nest built by both sexes in the crotch of limbs at tree trunk. 20 to 60 feet high. Always lined with wood chips and bark flakes, and usually with green leaves. 4-6 eggs, incubated mostly by female. Young hatch at around 32 days and fledge, or leave the nest, after a month.
Movement: Northernmost birds migrate, though many are sedentary, or stay put. May simply move in to lower altitudes for winter. In autumn females, both young and old, migrate before males. Males return first in spring.
Interesting Fact: Earlier this century these birds were
considered vermin, or pests and were killed in great numbers. A bounty was even offered and hunters were given money for killing these "chicken hawks". Their carcasses were tacked on barns and spread on fences to "teach other hawks a lesson." Today, these birds, as with all native bird species are very much protected by state and federal laws."
"Red-tail Behavior: Hunting tactics range from "sit and wait", where Red-tails perch out in open on phone poles and snags. Or soaring and scanning method of catching updrafts or thermals to observe large hunting area. Feeds on small to medium-sized mammals and birds, plus reptiles like snakes.
Nest and eggs: Sturdy stick and twig nests built in trees or on a cliff, often lined with bark, sprigs of evergreen and fresh green foliage. May be used year after year. Nests may be used by other birds like Great Horned Owls. 2-3 eggs and fledge youngsters at about 45 days.
Movement: Often year-round residents, but these winter birds may be northern migrants that make it this far south. Or maybe individuals that have found a steady food supply, especially during mild winters.
Interesting Fact: Maybe one raptor species that has profited from human presence. Forest clearing and agriculture practices have insured the Red-tail a spot in successful breeding niches. A very abundant and thriving species"
"Rough-legged Hawk
: Movement: Entire population of these arctic tundra breeders move in to lower U.S. for the winter. Migrate in valleys and not as high in the altitude as many other hawks. Many Red-tailed Hawks leave the area in the winter, so Rough-legs replace them with a similar diet. In Europe and Asia this same species is called a Buzzard which really refers to a buteo hawk and not a vulture.
Interesting Fact: In winter Rough-legs may communally roost, or spend the nights in one place in groups numbering from many to several hundred. This may be safety in numbers. Or it may be that birds congregate in areas that offer warmer temperatures throughout the night. This is called a "favorable microclimate".
Behavior: Feeds on 90% small mammals, lemmings in the north then voles in winter. Voles are small rodents like mice. Use vantage point to find prey rather than soar like Red-tail because thermals don't occur in cold winter weather. Sometimes hover like a huge, slow-winged hummingbird over fields looking for food."
"Swaines Hawk Behavior:
Unusual in that their diet varies with season. May hunt rodents and some small birds during the breeding season. Switch to a diet of insects like grasshoppers, locusts and dragonflies in the winter. Prey usually taken in flights from perches. Pasturelands and hayfields provide good foraging country.
Movement: Among the most migratory of North American raptors. Entire breeding population moves to Argentina, South America, to over-winter using mostly soaring and gliding as the power for their journey. Migrates only across land and as many as 400,000 seen in Veracruz, Mexico pooled up to avoid ocean crossing. Will not feed along the way. Total distance in 8 weeks of migration exceeds 7000 miles one way.
Interesting Fact: Organochloride pesticides recently killed tens of thousands of Swainson's Hawks on their wintering grounds in Argentina. These poisons were used to kill the insects that these birds feed upon. These pesticides are now banned, or illegal to use in the United States, but not so in South America."
