Species Description: The roseate spoonbill, Ajaia ajaia, is one of 14 species in the Order Ciconiiformes, or long legged wading birds. The spoonbill grows to approximately 32" in height (81 cm), with a wingspan of 53 inches (1.35 m) (Farrand 1988; Amos and Amos 1997). In adults, the head, neck, breast and upper back of A. ajaia are white; while its wings, lower back and legs are bright pink. A distinctive red band is prominent on the wing coverts, while the tail of the mature animal is orange. Juvenile birds appear generally white or pale pink in color and have a feathered head (Farrand 1988). The bill of A. ajaia is long and flat, with a spoon-tipped bill, a specialized adaptation for tactile feeding.
Potentially Misidentified Species: From a distance, A. ajaia can be confused with the greater flamingo, Phoenicopterus ruber, due to the similarity of body color in both species. However, the roseate spoonbill is generally smaller than the flamingo, with a shorter neck, and a longer, spoon-shaped bill.
Regional Occurrence: A. ajaia occurs from southeastern Georgia and Florida through the Gulf of Mexico, south to Argentina (Le Grand 1980; Robertson et al. 1983), with Cuba potentially being an area that acts as a source population for some sub-adult birds that eventually arrive in Florida Bay (Allen 1942; Robertson 1983). The Florida population is distinct from the Texas and Louisiana populations.
IRL Distribution: A. ajaia occurs lagoon-wide, but is most common in the estuaries surrounding the Cape Canaveral area.
Age, Size, Lifespan: The roseate spoonbill, Ajaia ajaia, grows to a height of approximately 32 inches (81 cm), with a wingspan of 53 inches (1.3 m) (Farrand 1988).
Abundance: The breeding population of the roseate spoonbill in Florida numbered as few as 30 pairs in 1942 (Allen 1942). The species was nearly extirpated from Florida and Texas from the late 1800s through the mid-1930s (Powell et al. 1989) due to the impacts of human harvesting for both food and feathers for the millinery trade. Following protection efforts, spoonbills reestablished small populations that grew quickly. By 1978, the Florida population had increased to approximately 1400 pairs (Robertson et al. 1983). However, later surveys (Powell et al. 1989) reported the number of breeding pairs in Florida Bay to be 400-450, and a recent Everglades National Park publication estimates only 100-200 breeding pairs in Florida Bay. In Texas, a 1979 survey estimated the number of breeding pairs at 2,500 (Blacklock et al. 1979).
Reproduction: In some areas, the breeding season of A. ajaia is somewhat influenced by local rainfall patterns (Leber 1980). In a Costa Rican study, for example, Leber (1980) observed that both roseate spoonbills and wood storks nest during months when rainfall totals begin to decrease. Kahl (1964) suggested this pattern may be related to the increase of food availability to both adults and chicks as water levels in estuaries decrease throughout the dry season. In Florida, spoonbills commonly nest among several other species of wading birds. Spoonbills arrive in the nesting colony between October and December (Leber 1980; Robertson et al 1983) and leave the area by late March or April (Roberston 1983), with nesting having no apparent correlation to rainfall patterns. In Texas, breeding adults begin to congregate in mid-March. Pairing begins by mid-April, and nesting by late April or early May. Egg laying generally occurs in mid-May.
In Costa Rica, spoonbill nest density in a mixed colony was approximately 2.2 nests per square meter in the preferred core area of the colony, versus only 0.8 nests per square meter at the periphery of the colony (Leber 1980). Nests are built in mangroves or other available trees and shrubs, and are usually located within 1 meter of the main trunk of the tree. Nest height averages approximately 2.7 m above the ground in Costa Rica (Leber 1980), while those in Texas were observed at lower heights, primarily within 1 meter of the ground (White et al. 1982). Nests are often concealed by overhead vegetation (Leber 1980) and are constructed of plant material that is abundant near the nest site. Dead twigs form a platform approximately 0.5 m in width upon which live and dead stems of other vegetation are laid to a depth of approximately 6 cm (White et al. 1982). Activities of the nesting pair eventually form a shallow depression in the nest into which the female lays its eggs.
Clutch size in Florida populations of A. ajaia averages between 1.9 - 3.3 eggs per clutch (Leber 1980), while in the Texas population, 2 - 4 eggs per clutch is common (White et al. 1982). Eggs are incubated 22 - 23 days, and young fledge between 35 - 42 days. One brood per year is produced.
Nest success in spoonbills is known to vary from year to year depending upon environmental conditions. No figures are available for hatching success in Florida; however, in Costa Rica, hatching success averages approximately 74%, among the highest rates for large wading birds. In Texas, hatching success has averaged 73%, with nest success as high as 87% (White et al. 1982). Much of the mortality among eggs is accounted for by failure of the eggs to hatch, and to death within the first 2 weeks of life (Rodgers 1980; White et al. 1982). Adults startled from nests can often brush or kick eggs and chicks out of the nest. Allen (1942) observed that spoonbills were highly sensitive to disturbances around the nest site, with frequent disturbance sometimes leading to a complete disruption of the breeding cycle and abandonment of the nest. Additionally, snakes and avian predators such as vultures and even pelicans have been observed preying upon both eggs and chicks. White et al. (1982) observed that the mortality rate among nestlings in Texas averaged 32% over 3 years, with most nestlings lost within 2 weeks of hatching. They estimated that half of the chicks were lost to predators, or to other unobserved causes, while half were found dead in or near the nest.
Embryology: The incubation period in Ajaia ajaia lasts 22-24 days, with adult females laying one egg every other day (Allen 1942; White et al. 1982). Eggs hatch in the order in which they were laid, with chicks hatching every other day (White et al. 1982). At hatching, chicks weigh approximately 50 g, and tend to gain an additional 9 g over the next several days. After about day 4, however, they rapidly gain weight; and by day 16 they achieve approximately half adult weight (White et al. 1982).
Chicks fledge at approximately 6 weeks of age, and by early July, the young hatched in late April are able to fly several hundred meters under their own power. Birds begin to disperse from the nesting area by early August, with few remaining at the end of September (White et al. 1982).
The skin, jaws and legs of newly hatched chicks are a uniform pink color, the feather tracts covered by thick white down that dries and becomes fluffy within 12 hours after hatching. 2 days after hatching, the eyes open. Feather development begins with the emergence of the feather sheaths of the flight feathers at about day 5. The rest of the body remains covered in down for approximately 3 weeks, and at this time the feather sheaths of the other major feathers begins to emerge. Feather growth takes 3 weeks to complete, with full development being complete 42 days after hatching (White et al. 1982). By this time, they young are fully capable of flight and are thus considered fledged. Full adult plumage does not appear until juveniles are approximately 3 years old, but there is significant variation among individuals (White et al. 1982).
Interestingly, bill morphology of hatchlings is not the characteristic spoon-shaped bill found in adults (White et al. 1982). Rather, young chicks have short, soft bills that are somewhat leathery. The bill tip begins to widen at 9 days of age, and by 16 days, it takes on the shape of the adult bill, and continues to lengthen as the chick ages.
Organochlorides such as DDE and PCBs have been shown to be the primary pollutants which occur in A. ajaia eggs. White et al. (1982) found DDE present in all eggs analyzed, while PCBs were present in 90% of samples. Generally, organochloride levels tended to be under 2 ppm, though some spoonbill eggs contained more than 15 ppm. Eggshell thickness was shown to be approximately 5% thinner than in the pre-DDT age, but no biological significance was assigned to this finding, as it was determined that the percentage difference was within the range of intraclutch variation (White et al. 1982). Spoonbills appear to be somewhat less sensitive to organochloride pollution that certain other species such as the brown pelican. Pelicans suffer nest failure when eggs contain a concentration of DDE greater than 2.5 ppm. While over 30% of the eggs in the White et al. (1982) study had DDE levels higher than 2.5 ppm, and some eggshell thinning was detected, no population declines or major reproductive failures were observed.
A. ajaia is a heterotroph that feeds on small fishes, shrimps, crabs and other epibenthic and benthic species. It feeds by moving its bill slowly through the water as it wades, straining out food items, and occasionally snapping its bill closed upon detecting larger prey (Farrand 1988).
Associated Species: A. ajaia is found nesting with wood storks (Mycteria americana)(Leber 1980), great egrets (Casmerodius albus), great blue herons (Ardea herodias), snowy egrets (Egretta thula), cattle egrets (Bubulcus ibis), tricolored herons (Hydranassa tricolor), black-crowned night herons (Nycticorax nycticorax), and laughing gulls (Laras atricilla).
Special Status: This species is not federally listed as threatened or endangered, but in Florida, is considered a Species of Special Concern (SSC).
During the late 1800s, roseate spoonbill populations from Florida through Texas were nearly extirpated due to trappers and hunters who killed the birds and collected their feathers for the fashion industry. By the 1940s, Allen (1942) reported that the breeding population of spoonbills in Florida may have numbered as few as 30 nesting pairs. Protection efforts after that time aided the birds in reestablishing nesting colonies, and by the late 1970s, the Florida population was estimated to be approximately 1,400 breeding pairs (Robertson et al. 1983).
Today, habitat loss and degradation of foraging and nesting habitats are the primary conservation concerns for roseate spoonbills in the United States (Powell and Bjork 1989, Martin 1991, Bjork and Powell 1996, Gawlik et al. 1998). In Florida, many nesting sites are already protected as part of the State and National park systems (Everglades National Park, Tampa Bay Sanctuaries, Merritt Island National Wildlife Refuge, etc.) but foraging habitat remains vulnerable to human development and disturbance (Bjork and Powell 1996).
Spoonbills have a preference for their feeding locations to be close to colony sites; thus, loss of foraging habitat could cause shifts in breeding locations. Evidence from the Florida Keys shows that loss of spoonbill feeding areas due to development from 1955 - 1985, likely caused breeding sites to be moved from the southeastern region of Florida Bay to more northern areas as mangrove habitats were eliminated (Powell et al. 1989; Bjork and Powell 1994). In Texas, Gawlik et al. (1998) reported that serious population decreases of nesting spoonbills in the Galveston Bay Estuary were concurrent with the loss of feeding grounds on coastal marshes.
Since 1979, the roseate spoonbill has been listed by the State of Florida as a Species of Special Concern. Prior to 1972, it was listed in Florida as Endangered, but was downlisted to Special Concern status when the category was first adopted (Bjork and Powell 1996). With the designation of Special Concern status in Florida, it is recognized that roseate spoonbills are vulnerable to habitat alteration or destruction, and are negatively impacted by human disturbance. Spoonbills are also classified as Rare by the Florida Committee on Rare and Endangered Birds and Animals (Bjork and Powell 1996).
Throughout Florida (Bjork and Powell 1994, 1996, Smith and Breininger 1995), multi-species protection efforts are being undertaken to conserve existing populations of wading birds, and to promote their future growth. Habitat protection measures are effected through both land acquisition programs and ecosystem restoration efforts. In south Florida, for example, approximately 50% of the remaining mainland mangrove area east of U.S. Highway has been purchased by the South Florida Water Management District and Miami-Dade County (Dumas 2000), with ongoing acquisitions attempting to secure the remaining mainland mangrove areas.
Ecosystem restoration efforts are also underway as the importance of natural water flows and water level fluctuations are increasingly recognized. The Comprehensive Everglades Restoration Plan, delivered to Congress in July 1999, is currently being implemented. This plan includes restoring the hydrology of all major estuaries from Caloosahatchee River on the Gulf Coast to St. Lucie Estuary on the Atlantic Coast, based on a hydrology model that mimics pre-drainage conditions for salinity, freshwater flow volumes and timing, duration of flooding, and depth of water (Dumas 2000). At Kennedy Space Center, mosquito impoundments are being managed to maintain favorable water levels and salinities for wading bird foraging and nesting (Smith and Breininger 1995).
Spoonbill and other wading bird populations will continue to be monitored to determine whether further protections are necessary. Spoonbills in Florida Bay may be a key indicator species of ecosystem health, and long-term changes in their population sizes, annual reproductive success, and colony distribution patterns are expected to show how effective regional restoration efforts have been.
Benefit in the IRL: Aesthetic, ecological.
Economic Importance: None. A. ajaia was formerly hunted both for its colorful plumage, and to a lesser degree, for food. Today, however, it has no direct economic importance.
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