Jacanidae – Jacanas

The Jacanidae (Jacanas) family is related to the waders, but sufficiently distinctive to merit its own family. The order Charadriiformes also includes Pluvianellidae (Magellanic Plover), Chionidae  (Sheathbills), Burhinidae (Thick-knees & Stone Curlews), Pluvianidae (Egyptian Plover), Ibidorhynchidae (Ibisbill), Recurvirostridae (Stilts & Avocets) Haematopodidae (Oystercatchers), Charadriidae (Plovers & Lapwings), Pedionomidae (Plains Wanderer), Thinocoridae (Seedsnipes), Rostratulidae (Painted Snipe), Scolopacidae (Sandpipers), Turnicidae (Buttonquails), Dromadidae (Crab-Plover), Glareolidae (Coursers & Pratincoles), Stercorariidae (Skuas), Alcidae (Auks) and Laridae (Gulls, Terns & Skimmers). There are just eight species of birds, in six genera.

Jacanas are sometimes referred to as Jesus birds or lily trotters, because their very long toes enable them to walk across the surface of lake vegetation. They are found worldwide within the tropical zone. They are identifiable by their huge feet and claws which enable them to walk on floating vegetation in the shallow lakes that are their preferred habitat. They have sharp bills and rounded wings, and many species also have wattles on their foreheads.

Comb-crested Jacana Irediparra gallinacean – ©Dubi Shapiro

Jacanas were once placed in the family Parridae based on the genus Parra but the family name is now Jacanidae based on the type genus Jacana. The family is placed within the order Charadriiformes under the suborder Scolopaci and is a sister of the Rostratulidae (Painted-snipes). They have 10 tail feathers unlike most others wader groups which have twelve. They have a rudimentary caecum.

There is some sexual dimorphism, female jacanas are larger than the males. The latter, as in some other wader families like the phalaropes, take responsibility for incubation, and some species (notably the Northern Jacana) are polyandrous. However, adults of both sexes look identical, as with most shorebirds. They construct relatively flimsy nests on floating vegetation, and lay eggs with dark irregular lines on their shells, providing camouflage amongst water weeds.

African Jacana Actophilornis africanus – ©Dubi Shapiro

The eggs are slightly smaller than in comparable species and it has been considered that this may be due to an evolutionary trade-off given the larger number of clutches that are laid. Male jacanas brood eggs between the wings and the body. This wing-brooding may be assisted by a special adaptation in the wing bones with either a broadening of the radius or a widening of the gap between the radius and ulna. Young chicks may also be held under the wing and transported to safety by the parent bird in some species. Young chicks dive underwater and stay submerged with only their bill out of water. Some adult jacanas also use the same technique. African jacanas go through a simultaneous moult of their flight feathers leading to a period of flightlessness. Their moult is related to their ability to breed opportunistically based on the availability of rains.

Their diet consists of insects and other invertebrates picked from the floating vegetation or the water’s surface. Most species are sedentary, but the Pheasant-tailed Jacana migrates from the north of its range into peninsular India and southeast Asia.