Resumen de THE NEST AND EGGS OF BLACK-CAPPED SPARROW Arremon a. abeillei (PASSERELLIDAE) IN SOUTHWESTERN ECUADOR
I describe the nest and egg of Black-capped Sparrow (Arremon a. abeillei), providing the first substantiated information on its reproductive biology and the first report of brood parasitism by Shiny Cowbird (Molothrus bonariensis). I studied 7 nests at two locations in southwestern Ecuador. Nests are enclosed, oven-shaped structures with a side entrance, concealed amongst leaf litter on either flat sloping ground. Confirmed clutch size at one nest was 4 eggs, and 13 eggs varied from very pale buff to pure white, sparsely marked with dark brown or black flecks, small spots, and short scrawls. Nest architecture is similar to that of congeners traditionally placed within Arremon and Lysurus, and to members of the genus Arremonops, but differs from the open-cup nests of congeners historically placed in the genera Buarremon or Atlapetes. Egg coloration reflects similar relationships within these genera.
