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THE RAPTORS OF IOWA

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By Dean M. Roosa, Jon W. Stravers, Bruce Ehresman, Rich Patterson

UNIVERSITY OF IOWA PRESS

Copyright © 2013 University of Iowa Press
All rights reserved.
ISBN: 978-1-60938-166-0

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Excerpt

CHAPTER 1

TURKEY VULTURE

Cathartes aura

These common summer residents arrive in Iowa early in March; most are gone by mid October. They nest sparingly, mainly in south central Iowa. They form communal roosts, principally on wooded bluffs along major streams; some such roosts have been in continual use for decades. Carrion feeders, they are often seen feeding on roadkill and seem to be one of the few bird species that can locate decaying food by smell from a distance. The black vulture, Coragyps atratus, while still considered of accidental occurrence in Iowa, has become of nearly regular occurrence in the last decade. This may be due to increased interest in the sport of birding or to the rapid climate change that is causing so many southern species to inch farther north. Look for it to be seen on a regular basis. In the meantime, study flocks of turkey vultures for a bird with notably shorter tail feathers, shorter and wider wings, and light-colored primary feathers, especially near the tip of the wing.

OSPREY

Pandion haliaetus

The osprey is an uncommon migrant, appearing in Iowa from early April to mid May and again in August and September. A fish feeder, it depends on open water to initiate migration. Records are becoming more frequent in recent years due to introduction attempts by the Iowa Department of Natural Resources and many conservation partners. Iowa's first nesting attempt was in 2000, and twelve out of sixteen nesting attempts in 2011 produced young.

SWALLOW-TAILED KITE

Elanoides forficatus

Our most elegant raptor is now of accidental occurrence in Iowa. It once nested sparingly in the state but disappeared prior to the twentieth century. With its long, forked, barn swallow–like tail, it is unmistakable. There have been three records in modern times: Black Hawk County in 1992, Cerro Gordo County in 2000, and Johnson County in 2004.

MISSISSIPPI KITE

Ictinia mississippiensis

This graceful bird now regularly occurs in Iowa, being reported each year. It returned in 1978 after an absence of some seventy years. There are historic records of nesting in Iowa; in modern times, it has nested in Polk County in 1995 and succeeding years, and there is recent evidence of probable nesting in Ottumwa.

BALD EAGLE

Haliaeetus leucocephalus

What a remarkable story surrounds our national symbol in Iowa! The bald eagle seems to have disappeared from Iowa as a nesting species around 1905, reappearing in Allamakee County in 1977. Since then it has spread statewide, with the most recent nest count being approximately three hundred nests in ninety-three counties. It congregates near open-water sites along larger rivers, especially the Mississippi, where it feeds on fish and waterfowl. Young eagles are solid brown, achieving their white heads and tails around age four. The white feathers of the adult's head make this bird eminently recognizable (see page iii); its immaculate appearance, both regal and untamed, is a testament to its endurance as our national symbol. In recent years, the world has been able to watch nesting bald eagles via the popular Decorah eagle cam.

NORTHERN HARRIER

Circus cyaneus

There is no mistaking the characteristic flight of the northern harrier. It flies low over grasslands, quartering section by section. The white rump patch is a definitive field mark. A fairly common migrant, the harrier is most frequently spotted from mid March to mid April and again from mid September to mid October. It prefers native prairie for nesting; both habitat and bird are rare in Iowa.

SHARP-SHINNED HAWK

Accipiter striatus

This exciting accipiter is a common migrant, seen in Iowa from mid March to mid May. It is an uncommon winter resident and apparently a very rare nester, with newly fledged young being seen in western Iowa and in Hardin and Lucas counties in recent years. It may have been a fairly common nester prior to the twentieth century.

COOPER'S HAWK

Accipiter cooperii

The Cooper's is a fairly common migrant, an uncommon nester, and an uncommon winter resident. It nests most frequently in south central and northeast Iowa, but its secretive habits may help it escape detection in other parts of the state. Its flight pattern and coloration have long caused this accipiter to be called the blue darter. It preys almost exclusively on small birds, and the short, rounded wings and long tail of this and other accipiters equip it elegantly for pursuing prey in heavy vegetation, usually trees. At the last instant before hitting the net at a banding station, this bird may spread its wings and tail, nearly stop in midair, rise over the net, and drop on the lure. The young are streaked with brown; adults have a slate back and barred front.

NORTHERN GOSHAWK

Accipiter gentilis

The goshawk, the largest of the bird hawks, is a rare winter resident in Iowa, appearing in late September and leaving by mid April. Periodically, the food base of this northern species declines, causing a southward invasion into neighboring states. Watching this wonderful large predator hunt is about as exciting as bird watching gets. Young birds of this and other accipiter species have yellow irises that darken with age; the irises of older birds are an intense amber.

RED-SHOULDERED HAWK

Buteo lineatus

The red-shoulder is an uncommon permanent resident and a rare nester. Its habitat is heavily wooded riparian areas, largely along the Mississippi River in eastern Iowa. It suffered a sharp decline as a nester in the 1950s and 1960s but seems to have a stable or even increasing nesting status currently. It often shares its habitat with the barred owl—the owl active by night, the hawk by day. The call of this midsize buteo is one of the few remaining Iowa sounds that drip with wildness.

BROAD-WINGED HAWK

Buteo platypterus

This midsize buteo is a common migrant but a rare nester in Iowa. During migration, it can move in large flocks of two to three thousand birds or more. It nests sparsely across the state, usually in deep woodlands. Iowa birds are gone by mid to late October and are virtually unknown in the state after that.

SWAINSON'S HAWK

Buteo swainsoni

This large buteo is a rare migrant and a very rare nester in Iowa. During migration, it is detected by mid April and is mostly gone after October. It is basically a Great Plains species, and its uncommon nest records occur in the northern and western parts of the state. It sometimes migrates in large flocks, although not as extensive as flocks of the broad-wing. Young Swainson's hawks can be notoriously hard to identify. A field aid is the slight dihedral attitude of the wings when soaring.

RED-TAILED HAWK

Buteo jamaicensis

Common to abundant throughout the year, this is the bread-and-butter raptor of the bird watcher, yet the four subspecies that occur in Iowa make it a challenge to identify: the western red-tail, the eastern red-tail, Harlan's red-tailed hawk, and Krider's red-tail. With its whitish head and nearly white tail feathers, the Krider's (see page x) is the most spectacular. It apparently formerly nested in Iowa; now it is infrequently seen primarily during migration. Some authors consider it a form, not a full subspecies. The red-tail almost certainly nests in every Iowa county, with the fewest nests in the nearly treeless counties in the northwest. It nests in isolated groves or at the edge of woodlands or even in solitary trees. It nearly always situates its nest so one or more open vistas allow it to hunt or to observe approaching danger.

FERRUGINOUS HAWK

Buteo regalis

One of our rarest raptors, the ferruginous hawk has a nesting range in western Nebraska as its closest approach to Iowa. It is very difficult to positively identify, and many records are not accepted as valid. This is our largest North American buteo.

ROUGH-LEGGED HAWK

Buteo lagopus

This uncommon although regular winter resident arrives in Iowa in late October and leaves by late March. Its nesting range is the Arctic tundra, and its periodic incursions into northern states depend upon the availability of food. A large raptor hovering over an open field in winter is nearly always a roughleg. Two color phases—dark and light—occur in Iowa; light-phase birds seem to be more common.

GOLDEN EAGLE

Aquila chrysaetos

Here is royalty in the minds of many birders. This western species is a rare migrant and a rare winter resident. Increased observations in recent years are probably due to an increased interest in ornithology but may also reflect increased human activity in its western range. Apparently a few pockets in Iowa, notably along the Upper Iowa and Mississippi rivers in Allamakee County, have been traditional wintering areas for golden eagles since at least the mid 1800s.

AMERICAN KESTREL

Falco sparverius

This small falcon, often called a sparrow hawk, is common as a summer resident, less so as a winter resident, and often abundant during migration. The Iowa Department of Natural Resources, in conjunction with the Iowa Department of Transportation, initiated a nest box program along interstate highways in the early 1980s, and it is now common to see this species hovering over grassy ditches in pursuit of prey or perched on highway signs.

MERLIN

Falco columbarius

The midsize merlin is a rare migrant and a rare winter resident, first occurring during migration in late March and again in late August. A few very old nesting records exist. Two subspecies of this falcon occur in Iowa: the taiga merlin and the Richardson's or prairie merlin, a pale form.

GYRFALCON

Falco rusticolus

The largest of the North American falcons lives mainly in the Arctic; it is of accidental occurrence in Iowa, with fewer than ten documented reports. The first acceptable records, from 1992 and 1993, were of gray-phase immature birds.

PEREGRINE FALCON

Falco peregrinus

The crow-size peregrine falcon is uncommon during migration but is becoming more common due to a reintroduction program started by the Iowa Department of Natural Resources. Falconers, who were at the heart of the reintroduction efforts, led the way toward unlocking the secrets of captive propagation of this and other raptor species. After an absence of some thirty years, natural nesting in historic sites is now occurring.

PRAIRIE FALCON

Falco mexicanus

Records of this rare winter resident come mostly from the western half of Iowa. Observations span from very late August through very late April. This is another Great Plains species that wanders into Iowa after the nesting season. It rarely engages in the spectacular stoops of the peregrine falcon but operates much closer to the ground, often tail-chasing its prey.

BARN OWL

Tyto alba

The barn owl has tough sledding in Iowa because we are at the very northern edge of its range. Too bad, because it is one of our most interesting owls. Nearly worldwide in distribution, it is very beneficial to farmers, to orchardists, and to humans in general since its large broods require a constant supply of food. The state's release program met with limited success because of less-than-ideal habitat conditions probably related to climate change; however, a nest box program for this owl is working.

EASTERN SCREECH-OWL

Megascops asio

The eastern screech-owl has been a fairly common permanent resident. However, records from the current Breeding Bird Atlas Project suggest that its numbers are declining. Whoever named this owl apparently did not hear its tremulous, descending, haunting warble or whinny, which is certainly not a screech; its lonely call also smacks of mystery and Halloween spookiness. The two main color phases—rufous and gray—seem to be nearly equally distributed in Iowa. One of our most beneficial birds, the screech-owl responds well to placement of nest boxes, and recorded calls played during surveys evoke good responses, implying that there may be many more owls than casual observations reveal.

GREAT HORNED OWL

Bubo virginianus

This common permanent resident and common nester is one of our most efficient predators. It likely nests in every Iowa county because it utilizes a variety of nest structures, preys on a wide variety of birds and mammals, and is not bothered by the presence of humans and human habitation. Its low, melodious call—common in Iowa—is often heard in movies when a spooky night scene is required. Occasionally individuals of the very pale northern subspecies are found as far south as central Iowa.

SNOWY OWL

Bubo scandiacus

The snowy is a rare winter visitor but is present in our state every year. It arrives as early as October and is normally gone by late March. Periodically, large invasions occur when lemmings, its principal food base, are in short supply in the Arctic. This is one of the few owls active during daylight.

NORTHERN HAWK OWL

Surnia ulula

This is an accidental visitor to Iowa, with only two accepted records, one from Black Hawk County in 1981 and 1982 and one from Worth County in 2004 and 2005. As its name implies, its general shape and perching attitude are somewhat hawklike.

BURROWING OWL

Athene cunicularia

The burrowing owl is a Great Plains species that rarely nests in Iowa, and these nests, as expected, are mostly in the western half of the state. It is our only owl that nests underground. In its principal range, it uses prairie dog burrows for its nest; in Iowa, it probably uses badger dens.

BARRED OWL

Strix varia

The booming call of the barred owl is familiar to anyone even slightly interested in birds. Perhaps our least-studied Iowa raptor, it is a fairly common nester in deep woods, generally in river bottoms, often sharing its habitat with red-shouldered hawks at different times of the day and night. It occurs commonly in the east and southeast parts of the state but becomes less often seen or heard as one travels to the northwest counties.

GREAT GRAY OWL

Strix nebulosa

This very large owl is of accidental occurrence in Iowa. The fact that it is a bird of coniferous old-growth forests puts it in conflict with logging interests. Its conformation is similar to, though larger than, that of the barred owl, but it has yellow instead of brown eyes. Young nonnesting birds can be heard calling from the marginal habitat where they grow up; they compete for prime habitat when they become nesters.

LONG-EARED OWL

Asio otus

The crow-size long-eared owl occurs regularly but nests rarely in Iowa. Since it feeds on mice and uses old crow nests, it is difficult to understand why this owl is so rare here. In winter, conifer stands are good places to find it.

SHORT-EARED OWL

Asio flammeus

This owl is found in Iowa every year, but only a handful of nesting records exist. In Iowa, as with the northern harrier, the short-ear prefers native prairie for nesting; it seems less likely to use restored prairies or Conservation Reserve Program lands for nesting. This implies that it will be a rare summer resident here for the foreseeable future. This species is often active just at dusk.

NORTHERN SAW-WHET OWL

Aegolius acadicus

This, the smallest owl found in Iowa, is a visitor from farther north; it is reported every year starting in early October. It is not known to nest here. However, it nests close to the northeast corner of Iowa, where there is plenty of favorable habitat. The boreal owl, Aegolius funereus, a resident of boreal forests, is a bit bigger than the saw-whet owl, just as tame, and much rarer, with only one record from Iowa: Black Hawk County in November 2004. This bird was swept in with the dramatic owl invasion that occurred in northern states in the winter of 2004–05.
(Continues...)

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Excerpted from THE RAPTORS OF IOWA by Dean M. Roosa. Copyright © 2013 by University of Iowa Press. Excerpted by permission of UNIVERSITY OF IOWA PRESS.
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