ANNUAL CYCLES OF MIGRATORY FATTENING, REPRODUCTION AND MOLT IN EUROPEAN QUAIL (COTURNIX-COTURNIX)

Experimental studies of the physiological mechanisms underlying avian migration have concentrated on small passerines. The present study is concerned with the regulation of migratory fat deposition in a gallifo rm, the European quail (Coturnix coturnix). The increased mass associa ted with migration was due exclusively to the deposition of fat wherea s the increased body mass of laying females was due to increases in le an tissue and water as well as fat. Annual cycles of body mass, moult, gonadal size and plasma luteinizing hormone were measured every other week in captive males and females held outdoors under natural dayleng ths and temperatures in Bristol, UK (51-degrees 27'N). Males and femal es showed two peaks of fat deposition each year which occurred at the migratory passage times reported in wild birds. Luteinizing hormone le vels and gonadal size increased in parallel with vernal fat deposition , and remained high until late summer. The pattern of primary feather moult in the intact birds was similar to that of wild quail, with moul t following gonadal regression and being suspended during autumnal fat tening. Castration of European quail did not inhibit the expression of migratory fattening, as it does in certain passerines. In fact, castr ates displayed fattening cycles that were more clearly defined and of greater amplitude than those in the intact males. The annual cycle of European quail differs from that of other well-studied passerine migra nts such as Zonotrichia sparrows, and this is most likely associated w ith differences in breeding ecology, In addition, the ability of quail to express vernal fattening independently of the presence of the gona ds suggests that taxonomic differences between migratory species are a lso apparent in the physiological mechanisms of migratory fattening.