is believed to be extinct, having been last recorded in 1952 (and described only in 1946). Their habitat ranges from high elevation lakes and marshes to low elevation lakes and rivers and coasts in open country. Breeding The nest is placed on the ground in vegetation close to water. It is lined with grass and down. The clutch is 4 to 10 eggs which hatch after incubation for around 26 days. The chicks have dark brown down above and yellow down below. Physiology In high altitude populations of yellow-billed pintail, hemoglobin has a higher affinity for oxygen than in lower altitude populations, which can be attributable to substitutions in their beta-globin gene. These substitutions are shared by speckled teal because of introgressive hybridization between the two species. Gene flow between populations also suggests that yellow-billed pintails that are heterozygous for the βA hemoglobin subunit may be able to acclimate to high altitudes more efficiently than those that are homozygous for the βA hemoglobin subunit. Gallery References yellow-billed pintail Birds of South America Birds of the Falkland Islands Birds of islands of the Atlantic Ocean Birds of subantarctic islands yellow-billed pintail yellow-billed pintail