Florida duck
| Florida duck | ||||||||||||
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Florida ducks |
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| Anas fulvigula | ||||||||||||
| Ridgway , 1874 |
The Florida duck ( Anas fulvigula ) is a duck bird that is counted among the swimming ducks. Two subspecies are usually given in the literature, but this division into subspecies is still controversial.
Florida ducks are not considered to be threatened, although they have lost much of their habitats, especially in Florida. In Florida, between 1975 and 1985, about 116,000 hectares of wetlands were converted into agricultural or settlement areas. Despite this habitat loss, Florida duck numbers remained stable between 1985 and 1993. The introduction of the mallard into Florida is considered to be a greater threat to this species . It is partly kept there as ornamental fowl, but is also released for hunting purposes. The mallard is closely related to the Florida duck and crosses with it very quickly.
Appearance
The Florida duck, which has no sexual dimorphism , is very similar to the female of the mallard. The body length of adult Florida ducks is 55 centimeters. They are therefore somewhat smaller than mallards and darker in color than these. The head is monochrome and there is no white on the tail. There is also a similarity to the North American dark duck ; However, this is darker in the plumage and has a purple wing mirror .
The plumage of the Florida duck is medium to dark brown. The body feathers have a relatively wide light brown border, which gives the duck a scaly appearance. The cheeks and throat are light brown. With some individuals they are finely dashed, with other individuals these dashes are missing. The wing mirror is green-blue and in most individuals does not have a white border. The beak is bright yellow with a striking black beak nail. In females, the color of the beaks can appear a little more dull. The legs are orange, the eyes brown. There is no seasonal dimorphism . Young ducks are similar to adults, but their pen-and-ink drawing is not yet as pronounced.
The chicks are very similar to the chicks of the mallards. On the upper side, however, they are more olive-brown and the yellowish body parts are somewhat more dull than in this species. The chicks have four brownish-yellow colored spots on their back, a noticeable dark eyebrow and a dark ear spot. The legs, feet and beak are black.
distribution
Two populations of Florida ducks are distinguished. One population, sometimes referred to as the subspecies Anas fulvigula maculosa , lives on the coast of the Gulf of Mexico between Alabama and Tamaulipas , Mexico. Outside of the breeding season, individual ducks of this population migrate further south and then reach Veracruz . The second population - classified in part of the literature as the nominate form Anas fulvigula fulvigula - consists of Florida resident birds that occasionally migrate northward to the US state of Georgia . This disjoint distribution pattern corresponds to that of the sandhill cranes , which were still found in this region in historical times. This population has the highest distribution density at Lake Okeechobee . This lake is located in the southern part of Florida between the cities of Orlando and Miami; it is around 56 km long, up to 48 km wide and covers a water surface of around 1890 km².
Duration
The western population fluctuates depending on the habitat conditions along the Gulf Coast. In years when there is abundant rainfall and therefore sufficient breeding water, the autumn population can be 200,000 to 250,000 individuals. In the last few decades, this population has expanded even further north, mainly using rice-growing areas as breeding waters. The eastern population is much smaller, estimated at 56,000 Florida ducks.
Habitat and general behaviors
The Florida duck lives in both fresh and brackish water . These include ponds , marshland, larger cattle troughs, flooded fields, and rice-growing areas. Islands off the coast are also settled if they offer suitable conditions.
Of all the swimming ducks in North America, the Florida duck is the species that forms the smallest flocks. Between February and July, the animals usually live in pairs. In the period from September to October, when the postnuptial moult is complete, up to 3,000 Florida ducks can be found in very nutrient-rich waters. In November, however, these swarms split up again into smaller groups.
food
Florida ducks spend around 43 percent of their time foraging for food between September and February. The food composition depends on the habitat and the season, but consists mainly of vegetable food. These include the seeds of grasses and sedges, as well as the stems, leaves and roots of aquatic plants. The animal diet of Florida ducks includes mollusks, insects, crustaceans and fish. Fish can even represent the largest part of the diet, depending on the season. This is especially true for the moulting period.
Florida ducks look for food in water depths of less than 30 centimeters, preferring places where plants protrude from the water. They filter through the substrate or look for food on the surface of the water, while they either swim on the water or stand in shallow water.
Reproduction
The Florida duck is a seasonally monogamous species of duck. The couple bond lasts for a period of three to six months. The pair bond begins in August; in September about 71 percent of all females are mated, in January this figure is 96 percent and in February the pair bond is complete.
The first nests will be built from January. The breeding season extends into August, but its peak is in March and April. The nests are built on the ground between dense vegetation. The nest density can be up to three nests per hectare. The laying distance is one egg each. After the fifth to sixth egg has been deposited, the nest cavity is padded with down. The full clutch has seven to fourteen eggs; the average is 10.4 eggs. 95 to 96 percent of all eggs are fertilized. The female breeds alone. The breeding season averages 26 days. During the breeding season, the female spends an average of 83 percent of her time on the clutch. The male stays close to the female until the start of the breeding season, then the pair bond loosens. From around the end of July the males gather in small swarms and go through the postnuptial moult.
Chicks hatch from 28 to 74 percent of the clutch. This wide range of clutch success depends on the nest location and how large the density of predators there is. Florida ducks react to loss of eggs by starting breeding again. This can happen up to five times per reproductive period.
The chicks are sensitive to excessively high salinity in the water (salinity greater than 12 ppm ). In brackish water areas they show a lower growth rate and a higher mortality rate than in fresh water areas. Until about the 21st day of life they live exclusively on invertebrates. At 45 to 56 days they can escape predators by flight. From the 63rd to 70th day of life, they are able to cover even longer distances while flying.
The oldest wild Florida duck lived to be 13 years old. However, the average life expectancy is significantly lower. Fledgling male Florida ducks have a life expectancy of 2.5 years. That of the females is slightly lower, as they are at a higher risk of attacking a predator during the breeding season. Their life expectancy is only 1.4 years.
Systematics
DNA research suggests that the Florida duck is most closely related to the dark duck . Contrary to what was assumed for a long time, the degree of kinship with the mallard is not so high. The DNA analyzes also show that the two populations differ genetically from each other due to their small distribution area and their low tendency to migrate.
As with a number of swimming ducks, the Florida duck is able to produce reproductive offspring with both the dark duck and the mallard . The former has always occurred to a certain extent. Individual individuals of the migrating dark duck overwinter in the Florida duck's distribution area and occasionally do not move back to their breeding areas in the north in spring. With these dark ducks there were also matings. But this happened so rarely that the species was preserved as such. The matings with the imported mallard are classified as critical. Combined with habitat loss through conversion of the wetlands and the effect of global warming on the wetlands in southern North America, the crossing of the mallard can lead to a complete loss of the species.
supporting documents
Individual evidence
- ^ Kear, p. 520
- ^ Kear, p. 517
- ↑ Kear, p. 518
- ↑ Kear, p. 518
- ^ Kear, p. 519
- ^ Kear, p. 519
- ^ Kear, p. 519
- ^ Kear, p. 519
- ^ Kear, p. 519
- ^ Kear, p. 520
- ^ Kear, p. 520
- ^ Kear, p. 520
- ^ Kear, p. 520
- ^ McCracken, Kevin G .; Johnson, William P. & Sheldon, Frederick H. (2001): Molecular population genetics, phylogeography, and conservation biology of the mottled duck ( Anas fulvigula ). Conservation Genetics 2 (2): 87-102. doi : 10.1023 / A: 1011858312115 , PDF ( Memento of the original dated February 6, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. .
literature
- Janet Kear (Ed.): Ducks, Geese and Swans . Oxford University Press, 2005, ISBN 0198546459
- Hartmut Kolbe: The world's ducks . Ulmer Verlag, 1999, ISBN 3-8001-7442-1
- Christopher S. Smith: Field Guide to Upland Birds and Waterfowl . Wilderness Adventure Press, Belgrade (Montana) 2000, ISBN 1-885106-20-3
Web link
- Anas fulvigula inthe IUCN 2013 Red List of Endangered Species . Listed by: BirdLife International, 2012. Retrieved February 6, 2014.