is completely ignored. Present vegetation is dis- 

 tributed in zones away from the lagoon. The la- 

 goon flat at the water's edge is covered with alter- 

 nating strands of sedge {Sicyos sp.), heliotrope 

 [Heliotropium currasavicum) , and sesuvium (Se- 

 suvium portulacastrum) . The next zone is a knee- 

 deep mat of beach morning glory [Ipomoea pes- 

 caprae), which almost surrounds the lagoon. 

 Farther up the gradual slope above the water 

 table, morning glory is replaced by a dense belt of 

 bunch grass [Erogrostis variabilis), often mixed 

 with puncture vine {Tribulus cistoides) and boer- 

 haavia (Boerhaavia diffusa). Still farther up the 

 slope, the plant cover thins to scattered mats of 

 prostrate succulent boerhaavia interspersed with 

 bunch grass. Occasional clumps of scaevola 

 {Scaevola fructescens) are scattered about the 

 higher ridges of the island. Ducks use all of these 

 vegetation zones for feeding, although they are 

 restricted to the morning glory and bunch grass 

 interphase and boerhaavia zones when molting 

 and flightless (Warner 1963). Fresh or slightly 

 brackish water seeps are used for bathing when 

 available, but there are long periods when these 

 are not available. There is some evidence of salt 

 secretion by the nasal glands, and also that rain 

 water on bushes is used for bathing (Warner 

 1963). 



FOOD AND FORAGING BEHAVIOR 



The stomach of a male collected near a pond 

 was gorged with small flies resembling the com- 

 mon housefly (Fisher 1903). Warner (1963) 

 noted that sesuvium, so heavily utilized when it 

 was the major remaining vegetation on Laysan 

 during rabbit infestation, is now completely 

 ignored as food. Most feeding and other activity 

 begins at dusk and continues to about midnight 

 (Ely and Clapp 1973. Warner 1963). These ducks 

 are primarily insectivorous, at least during the 

 summer months (Ely and Clapp 1973). Warner 

 (1963) describes nocturnal feeding on cutworms, 

 which are larvae of a nocturnal moth {Agrostis 

 sp.), both from vegetation and the sand beneath, 

 and pursuit of brine flies along the lagoon edge. 

 He observed feeding on littoral invertebrates in 

 tide pools as well as on larvae and pupae of flies 

 and beetles in the sand around seabird carcasses. 

 He believed that plant materials were eaten, if at 



all, only incidentally to the animal food which 

 was actively sought. He noted that ducks follow 

 favored routes for feeding activities. He deter- 

 mined the home range to be about 0.81 ha, and 

 much smaller during the summer flightless period 

 while molting. 



SHELTER REQUIREMENTS 



When approached, the birds usually walk into 

 vegetation, and less often, paddle into the lagoon 

 or take flight (Ely and Clapp 1973). 



NESTING OR BEDDING 



The nest is a down-lined depression under 

 vegetation (Ely and Clapp 1973). One nest was 

 placed under a thick chenopodium bush close to 

 a pond. The shallow bowl was a little over 12.7 

 cm in diameter, formed of long, dry sedge stems 

 (Fisher 1903). 



RITUAL REQUIREMENTS 



None described. 



OTHER CRITICAL REQUIREMENTS 



None known. 



POPULATION NUMBERS AND TRENDS 



Fisher (1903) estimated their numbers at 

 less than 100 in 1903. Dill and Bryan (1912) 

 could not be sure of more than 6 individuals 

 in 1911. Munter (1915) counted 13 on the fresh- 

 water pond in 1915. J. S. Palmer (m Phillips 

 1923) reported about 35 in 1918. A. Wetmore 

 (in Phillips 1923) left 14 in 1923. Brock (1951) 

 found 33 in 1950. 



Never very common, they declined to mini- 

 mum between 1920 and 1930. A thorough 

 search in 1930 discovered only 1 female (Ely 

 and Clapp 1973). By 1957, the population had 

 recovered to an estimated 600 (Warner 1963). 

 Estimates fluctuated between 200 and 300 until 

 1969, then dechned to only 75 birds in 1970 

 (Fish and Wildlife Service, Ely and Clapp, Berger 

 1972; King in press). In 1972, the estimated 

 number was 175, but in 1973, they were down 

 to less than 40 (E. Kridler 1974 in King in press). 

 More recent counts are: July 1974—69, August 

 1975-251, May 1976-100, August 1976-287, 

 August 1977— 240, (Eugene Kridler pers.comm.). 



