ALL ABOUT SNAIL KITES
TABLE OF CONTENTS
and their arrival in Gainesville after Hurricane Irma
All images and text are (c) Copyright 2018 Paula Sharp & Ross Eatman. See Permissions.
ENDANGERED SPECIES STATUS
Snail kites (Rostrhamus sociabilis) are striking raptors that live in sawgrass marshes and similar habitats. Within the United States, snail kites are found only in Florida. The birds' diet consists almost exclusively of a freshwater mollusk known as the apple snail.
Snail kites are currently endangered and are protected by both federal and Florida law. The federal Endangered Species Act prohibits, inter alia, the birds' killing, harassment, capture or sale. The U.S. Fish and Wildlife Service recommends that people stay at least 500 feet from any active snail kite nests.
Snail kites' highly specialized diet has rendered them vulnerable to habitat loss, and their numbers within Florida are severely limited. As recently as 2009, snail kites' populations dipped to as few as 700-800 birds.
As noted below, snail kite populations have increased with the advent of an invasive apple snail, now common in Florida's wetlands. In recent years, however, everglades snail kite populations have been hit hard by dought and an especially destructive 2017 hurricane season.
SNAIL KITE IDENTIFICATION
Snail kites are among the most beautiful of American raptors. Male snail kites are a striking blue-grey with scarlet eyes. They have bright orange legs and feet and sharply curved, narrow black beaks topped with orange ceres (nostril areas). The snail kite's tail (whether male or female, adult or juvenile) is square, with a white base and black outer rim. Adult birds are as large as 17" high, with a 42" wingspan.
As shown in the photo strip below, this species exhibits notable sexual dimorphism. Adult female snail kites are are brown, with varying patterns of white on their faces, throats, chests and underwings. They tend to have distinctive white facial markings, including well-defined “eyebrows” made up of white feathers. Very old females may lack the eyebrows and be a darker brown with fewer pale feathers. Female adult snail kites have yellow or orange legs and ceres; and red or orangish-brown eyes.
Kites belong to the same bird family as hawks and eagles, Accipittridae. From a distance, the snail kite generally resembles a medium-sized hawk with broad wings. Snail kites are most likely to appear in wetlands that combine marshes overgrown with cattails and sawgrass, suitable for hunting snails, with nearby areas of shallow open water containing stands of trees and shrubs suitable for nesting.
Juvenile vs. female snail kites. Juveniles closely resemble adult females, and close inspection may be required to tell them apart. (Juveniles are birds in their first year.)
A few ways to distinguish juvenile and females snail kites are: (1) juveniles have large light-colored patches above their eyes and on their throats, but lack the well-defined white "eyebrows" characteristic of most adult females; (2) Juveniles have a larger proportion of buff or cinnamon-colored feathers where females have white ones; (3) the legs of juveniles may be yellow but not orange; and (4) the yellow area on the ceres of the juvenile kite is smaller and less well-defined than on adult females. (5) A useful way to identify an adult female is by eye color: while females have red or orangish eyes, juveniles have dark-brown or blackish eyes. (These features are elucidated in the photo strip below.)
Nonetheless, females and juveniles are often confused with one another. Females on the cusp of moving from the juvenile to adult stage often appear to have dark-brown eyes, even after the birds have become old enough to engage in nesting behavior. In areas where snail kites abound, local residents may swear that female snail kites never have red eyes. Nonetheless, the fact that adult females tend to develop red eyes has been recorded by the U.S. Fish and Wildlife Service and countless reputable birds guides (among them Peterson's Field Guide to Hawks; National Geographic's Field Guide to Birds of North America; Brown & Amadon’s Eagles, Hawks and Falcons of the World; Clark & Wheeler’s Field Guide to Hawks of North America; and Cornell's Birds of North America).
An adult female snail kite in flight
An adult male snail kite grasping an apple snail
A juvenile snail kite near the beginning of its first year
A female snail kite soaring over a marsh
A male snail kite with an apple snail retrieved from a marsh.
An adult male snail kite in flight. Male snail kites are a striking blue-grey. They have sharply curved, long and narrow black beaks; and orange or reddish-orange legs. The male birds' ceres (located at the base of the beak) are orange or reddish- orange, and the irises of their eyes are a striking red.
A male snail kite in its natural habitat - perched on a myrtle tree growing in the middle of a shallow lake
A female snail kite. Females are brown, with white "eyebrows" and yellow-to-orange ceres and legs. Fully adult females have red or orangish-brown eyes.
An adult female snail kite in flight: note the triangular black-and-white tail, a trait shared by both male and female snail kites. The feathers on the female's chest and lower body are brown and white.
The adult female's feathers under her wings are brown and white.
An adult male snail kite spreading its wings. The undersides of the wings of adult males are gray.
THE UNANTICIPATED BENEFICIAL EFFECT
OF EXOTIC SNAILS ON SNAIL KITE NUMBERS
At one time, the Florida apple snail (Pomaceae paludosa) was the primary food of snail kites, whose talons and sharply curved bills are keenly adapted to extract the mollusks from their shells.
Armed with gills as well as lungs, Florida apple snails live underwater in saltgrass marshes, coming up occasionally for air or to deposit eggs on aquatic plants. The snails require wetlands with limited drought periods, where water is shallow enough to sustain the plants on which the snails lay eggs.
By the turn of the millennium, habitat loss resulted in the decimation of the native Florida apple snail. The snail kite population accordingly fell into a rapid decline and courted extinction. Between 1999 and 2009, the Florida snail kite population plunged from 3,400 to its record low of 700-800.
The Island Apple Snail vs. the Florida Apple Snail
The survival of snail kites is due in part to one of the odder stories in the annals of invasive species history. Around 2001, an invasive mollusk known as the island snail (Pomacea maculata), originating in South America and the Caribbean, crept into Florida’s Lake Tohopekaliga, situated in Florida’s Kissimmee Chain of Lakes.
By 2006, the foreign island snail dominated the lake, and by 2009, this exotic mollusk had appeared in several Florida wetlands. It proved to be longer-lived as well as bigger than its Florida counterpart. The island snail was also more fertile and produced eggs that were highly resilient to environmental change and extended drought. The invasive mollusk quickly outcompeted native snail populations. Island snails are now endemic to wetlands throughout Florida.
Island snails are easily detected in a given wetland, because this species lays bright pink eggs on aquatic plants, just above the waterline. As shown in the photographs here, Florida apple snails lay eggs that are white. Their eggs are relatively large, in comparison with island apple snail eggs, and appear in relatively small clusters.
By contrast, the eggs of the exotic island apple snail are smaller and more densely packed. Eggs in a single cluster can number in the hundreds -- a trait that makes them particularly successful invaders.
Snail Kites' Adaptation to the Island Apple Snail
Countless reports have documented the deleterious effects of large exotic snail species on native snail populations and native plant life in marsh and swamp habitats. Among other qualities, invasive snails can consume native plants at a faster rate; affect nutrient flows in wetlands; and introduce parasites that threaten native fauna.
Nonetheless, the advent of the non-native island snails to Florida has had an unexpected positive effect on various Florida animal species that rely on snails for food. Among these are snail kites. (Limpkins, American Alligators, turtles and raccoons also dine on island snails.)
Because the exotic island snails are hardier and reproduce at a faster rate, the snail kite food supply has increased dramatically. This, in turn, has resulted in a significant growth in the numbers of snail kites in habitats throughout Florida. Snail kites are now more likely to nest, and juvenile snail kites more likely to thrive, in wetlands where the large, meaty and plentiful island apple snail -- two to five times larger than its Florida counterpart -- has taken hold.
In 2017, a group of University of Florida scientists discovered that the advent of invasive snails had impacted the Florida snail kite population in a novel way. Christopher Cattau, Robert J. Fletcher, Jr., Rebecca T. Kimball, Christine W. Miller and Wiley M. Kitchens reported their findings in a paper published in Nature, Ecology & Evolution. Snail kites, they had learned, were adapting rapidly to their new food source.
Findings showed that in fewer than ten years, snail kites’ bill size and body mass had increased substantially. Larger birds with larger bills were better equipped for removal of snail meat from the bigger shells of invasive snails.
The heftier size of the plentiful invasive snails rendered them a more rewarding food source than their native Florida counterparts. Swift adaptation to the exotic species thus aided the dwindling snail kite population. Cattau and his colleagues described this adaptation as an example of “phenotype plasticity,” or the ability of a species to alter its characteristics in response to environmental changes. The researchers heralded snail kite changes in bill size and body mass as evidence that phenotype plasticity may prove crucial to the survival of imperiled species in our rapidly-changing world.
The Florida apple snail (Pomacea paludosa). [lIlustration by Helen Lawson, 1845]
The white eggs of the Florida apple snail (Pomacea paludosa)
The pink eggs of the exotic island apple snail (Pomacea maculata)
The snail kite's sharply curved bill is designed to extract snails from their shells.
The native Florida apple snail (Pomacea paludosa)
These are the eggs of the Florida apple snail. Apple snails attach their eggs to the stems of aquatic marsh plants.
The recurved beak of a male snail kite, used for removing snails from snail shells. Apple snails are the preferred food of the snail kite.
An adult female snail kite's bill: Note how the top half of the bill fits into a groove in the bottom half. Snail kites' bills have become longer in response to the presence of the invasive island apple snail.
These are island apple snails (Pomacea maculata), an important food source for snail kites and other wild marsh birds. This exotic South American species has outcompeted the native Floridian apple snail.
These are the pink eggs of the island apple snail (Pomacea maculata). The island apple snail's eggs are densely packed; a single group of eggs can number in the hundreds.
The eggs of the native Florida apple snail, by comparison, are white and are far less commonly seen than the pink eggs of island apple snails. The native snail's eggs are also larger, less densely packed and found in smaller groupings.
A male snail kite with an island apple snail
CHANGES IN THE RANGE AND
POPULATION OF FLORIDA SNAIL KITES
Although snail kites are found in parts of Mexico, Central America, South America and the Caribbean, the birds' range in the United States is limited to the state of Florida. At one time, U.S. snail kite populations reached from the Everglades in Florida's southern tip, all the way to Northern Florida, including its Panhandle.
By the turn of the millennium, snail kites’ range had shrunk notably. In 2017, the U.S. Fish and Wildlife Service described the birds' range as reaching no farther north than the Upper St. Johns River near Orlando, located in central Florida. From there, snail kite populations extended southward along the Kissimmee River Valley, to Lake Okeechobee (Florida's largest lake, which forms the headwaters for the Everglades).
As noted above, snail kite populations steadily fell until 2009. With the advent and spread of invasive island snails, Florida snail kite numbers climbed from 700-800 in 2009 to an estimated 1200 birds in 2014.
A large proportion of the endangered birds concentrated in Lake Okeechobee. The Audubon Society reported that by 2016, the lake harbored 800 snail kite nests. A spring 2017 drought, however, precipitated a severe decline: a mere 135 nests were discovered that year. And while about a third of those nests were still active, Hurricane Irma hit.
Following the 2017 Hurricane season, the Audubon Society reported that Hurricane Irma had wiped out all of the 44 active nests of snail kites still roosting in Lake Okeechobee. Although some adult and juvenile birds escaped, countless eggs and nestlings had been destroyed.
Nonetheless, some hopeful news came from farther north in early 2018. In February, and again in April, 2018, snail kites were spotted in Sweetwater Wetlands Park of Alachua County, located in Gainesville, far north of the birds' expected range (111 miles north of Orlando). An additional banded male snail kite was sighted at neighboring Paynes Prairie Preserve.
In June, 2018, University of Florida wildlife biologist Brian Jeffrey surveyed 2500 acres of flooded prairie basin bordering Sweetwater Wetlands' public areas. He found eight unbanded snail kites and a nest containing three 3-week-old chicks. This news was heralded with considerable wonder and fanfare, because no snail kite nest had been seen in Gainesville for 99 years.
Natural vs. Human-altered Wetlands and the case of Gainesville's Sweetwater
Marshy habitats such as Gainesville's Sweetwater are known as "human-altered wetlands". Sweetwater itself is the result of an ingenious engineering plan, whose purpose was to restore natural water flow to neighboring Paynes Prairie Preserve -- a more than 1,300- acre expanse of formerly-drained wetlands -- and thus to increase conservation areas in Gainesville.
A 2016 study by environmentalists Kyle E. Pias, Robert J. Fletcher, Jr. and Wiley M. Kitchens charted the relocation of snail kites in what they termed “novel ecosystems” of Florida, that is, in newly-developed man-made wetlands occurring in cattle pastures, drainage areas, retention ponds and mitigation wetlands. Pias and his team discovered that the invasive island snail, armed with superior drought resistance than the Florida snail, is able to thrive in such areas.
Snail kites require wet habitats that have been flooded for at least 15-18 months. In addition, they need water that is relatively shallow, in which they can spy and capture snails that have climbed aquatic vegetation to come up for air or to lay eggs near the water’s surface. Kyle and his team found that man-made wetlands that provide such conditions, and that harbor significant populations of island snails, attract snail kites.
Nonetheless, the establishment of snail kites in man-made wetlands can prove perilous, because commercial development and other non-ecologically-minded objectives can result in sudden drops in water level that kill off snails. In addition, snail kite nests, ordinarily bounded by buffers of marshland waters, are more vulnerable to attack when drought converts wetlands into dry ground easily traversed by predators such as raccoons.
Protected man-made wetlands such as Sweetwater, because of their careful ecological monitoring, are better equipped to insulate snails and snail kites against environmental extremes. They thus may prove essential for the survival of the snail kite species. Sweetwater currently maintains a large population of island apple snails and a smaller one of Florida apple snails.
Snail kites there enjoy an added protection. The kites make frequent trips to Sweetwater marshlands bordering park boardwalks and paths -- and thus provide ample birding and photography opportunities. The birds' nesting places, however, are situated in nearby wetland areas inaccessible to the public. This helps insulate this endangered species from destructive sightseeing activities like those detailed below.
A female adult snail kite lifts an island apple snail from a Sweetwater Wetlands marsh.
A juvenile snail kite at Sweetwater looking down in flight, behavior typical of the species: the bird is looking for apple snails that have crawled to the water's surface.
A female snail kite standing thigh-deep in shallow water, hunting for snails at Gainesville's Sweetwater Wetlands in 2018.
A young female snail kite coming to rest on a snag at the edge of a Sweetwater marsh
A snail kite in its natural habitat: this adult female is resting on a swamp willow, surrounded by alligator flag and other marsh plants, which are rooted in shallow water. Behind the kite is a shallow lake.
A female snail kite in dawn light, lifting a snail from shallow water at Sweetwater. Deeper water would inhibit snails from laying eggs and make their capture more difficult for snail kites.
A young female snail kite at Sweetwater, looking down as it flies, a habit typical of snail kites: this bird is looking for apple snails in shallow marsh water.
The kite reverses course, plunging downward to nab a snail
The snail kite peers downward into the water as it approaches a snail.
The kite lands thigh-deep in the marsh
The shallow water of this Sweetwater marsh provides perfect hunting conditions for this snail kite. The kite continues to stare into the shallow water while readying itself to seize a snail with its talons.
The kite lifts an apple snail from the water.
RECOMMENDED CITATION FOR THIS PAGE:
Sharp Paula and Ross Eatman, "All About Snail Kites." Birds of the Florida Swamps. June 14, 2018. Web. [Date accessed] <https://www.florida-ecology.com/all-about-snail-kites>
RECENT CONTROVERSIES REGARDING
BIRD PHOTOGRAPHERS & SNAIL KITES
If you are a nature photographer interested in photographing snail kites, please keep in mind that these birds are protected by the federal Endangered Species Act. Section 9 of this act prohibits, among other things, the "taking" of endangered birds. Section 3(19) defines "take" to mean "harass, harm, pursue, hunt, shoot, wound, kill, trap, capture or collect or to attempt to engage in such conduct.” Florida's Administrative Code affords snail kites parallel protections under state law.
Photographers should exercise extraordinary care in avoiding nesting snail kites, absent a permit that allows nest observation for research or conservation purposes. On its website, the U.S. Fish and Wildlife Service recommends that people stay at least 500 feet from active snail kite nests -- a distance that most professional photographers would find beyond the reach of their equipment. If you approach nests more closely, you court felony charges by engaging in behavior deemed to "harass" an endangered species.
A recent highly publicized case of an Endangered Species Act prosecution involved snail kites. In 2014, a nature photographer who ran boat trips to view nesting snail kites on Lake Tohopekaliga -- at $300 per day, per customer- - was convicted of of violating the Federal Endangered Species Act. The charges against him carried a a maximum sentence of one year of imprisonment and a fine of $100,000. The case earned the Popular Photography headline:
Photog Could Face Jail Time, $100,000 Fine
for Disturbing Protected Bird Nests:
When the Endangered Species Act says 500 feet,
it doesn't mean ram your boat into the nest.
As related by Audubon Magazine, U.S. Geological Survey researchers reported that they had witnessed the photographer ramming his boat into reeds in close proximity to nesting snail kites. According to one researcher, despite warnings, the photographer subsequently pursued similar bird-harassing behavior on multiple occasions over the next two years.
While many boat tour guides act responsibly, others engage in brinkmanship with potentially disastrous consequences, both for the birds and themselves. The Lake Tohopekaliga photographer, under pressure of steep legal fees and the threat of a felony conviction, pleaded guilty to a lesser offense and received a reduced sentence -- community service, a $9,000 fine, two years probation, and a ban on his use of any snail kite pictures he had taken during the period of his prohibited activities.
Behavior disruptive to nesting snail kites is particularly likely to occur in instances where guides take large groups of tourists on boat trips to see nests. In such circumstances, the pecuniary rewards of pleasing multiple customers with conflicting goals may lead to cutting corners and legal violations. The presence of many people at a single time near nesting birds may itself prove problematic.
If you do choose to hire a boat to view snail kites in hard-to-reach areas, take pains to assure that your guide has a reputation for respecting wildlife, and that the endangered birds you intend to view are not on nests. When nesting snail kites are harassed or threatened even briefly, they may leave their nests temporarily, exposing their eggs to harsh weather conditions or predators. And try to remind yourself that if you're near enough to get a good shot of a snail kite nest, you're probably much closer than 500 feet.
The Audubon Society's Ethical Guidelines for Bird Photographers offer a common-sense approach for judging whether photographing a nesting bird (whether endangered or not) is appropriate. Audubon asks photographers to consider, among other factors, a given nesting bird's familiarity with human contact, as well as any obvious signs of stress exhibited by the bird. in your backyard or at popular rookeries, for example, birds may be unperturbed by the presence of a photographer, while birds in more remote places may be alarmed by the approach of humans. Nesting snail kites that inhabit difficult-to-access areas located along riverbanks or deep in marshlands may be particularly unaccustomed to the presence of people.
The photographer who avoids disrupting nesting snail kites will still find richly rewarding opportunities for viewing the kites in venues where they do not feel threatened. In many preserves and lakeside areas, snail kites comb the edges of marshes. They frequently approach shorelines, boats, boat launches and docks on their own initiative, while hunting for snails or temporary perches on which to which to rest. Snail kites' hunting behaviors - - acrobatic glides and sudden dramatic drops into shallow water to grab apple snails -- are beautiful and entertaining to behold, and well-worth photographing. The birds in themselves are striking and unique subjects even for still portraits.
A male snail kite perched on a marsh edge, surveying the water for snails. The bird's right leg has been tagged by researchers. Such tags aid scientists in tracking the numbers and movements of endangered species. (Click photo to enlarge)
A snail kite landing on a snag near the shore of a marshland
A juvenile snail kite resting on a myrtle tree
A female snail kite preparing the dive from a willow.