The Role of the Pituitary, Fat Deposition, and Body Weight in Bird Migration

Morphological Aspects and the Ecological and Mechanical Consequences of Fat Deposition in Wild Vertebrates

“…In both birds and mammals (14, 20,67,152,209,273,302,303) the quantity, anatomical location, and timing of fa t deposition are under tight physiological control. These animals do not start to gain weight "until the last possible moment" before hibernation or migration begins.…”

Energy Metabolism of Two Species of the Genus Emberiza as Correlated with Distribution and Migration

“…Altogether, some fifteen species of small migratory birds have been found to exhibit a distinct peak in weight in spring or autumn or both (see the reports by : ZEDLITZ 1926;GROEBBELS 1928GROEBBELS , 1932LrxsnALE & SmrxER 1934, according to WOLFSO::-< 1945~iERKEL 1937;PUTZIG 1939;BAmiGARTXER 1938;SHAw 1939, according to DE Bo::-<T 1947BLA..'\CHARD 1941;WOLFSO::-< 1945;DE BüNT 1947;ÜDUM 1949;ÜDl.DI & PE~SOX 1951;MARSHALL 1952;SCHILDMACHER 1952;and ScHILmiACHER & STEUBIXG 1952). Such a peak has not been demonstrated in non-migratory species, but in several cases there is an indication of weight increment during the cold season .…”

“…WOLFSOX (1945) and ÜDUM & PERKINSON (1951 ) assume deposits of fat to be an essential prerequisite for migration. There is, however, probably no absolute need for weight increment.…”

The Winter Society of the Oregon Junco: The Flock

“…The possibility that birds do migrate in integrated social groups has been conjectured occasionally in the literature and was given some substance when six Slate-colored Juncos were trapped in two successive years at a Massachusetts banding station (Whittle and Fletcher, 1924). The control of migratory flight is assumed to involve physiological changes in the organism including the deposition of fat, stimulated in part by environmental changes in, for example, temperature or the photoperiod (Odum and Perkinson, 1951;Wolfson, 1942Wolfson, , 1945Wolfson, , 1953, and there is the unstated assumption that these mechanisms exercise primary control, without intervention of social factors. Today this suggestion would be met with reserve.…”