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Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food‐bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of additional matings and by lowering the reproductive success of existing mates. Male warblers reduce the former cost by choosing the season of desertion and the latter is lowered by the female's high parental ability. A deserter was found to start moulting while his mate was still feeding his nestlings, and an earlier start to the moult may be the primary benefit that he gains. Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food‐bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of additional matings and by lowering the reproductive success of existing mates. Male warblers reduce the former cost by choosing the season of desertion and the latter is lowered by the female's high parental ability. A deserter was found to start moulting while his mate was still feeding his nestlings, and an earlier start to the moult may be the primary benefit that he gains. Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food‐bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of a...

Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food‐bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of additional matings and by lowering the reproductive success of existing mates. Male warblers reduce the former cost by choosing the season of desertion and the latter is lowered by the female's high parental ability. A deserter was found to start moulting while his mate was still feeding his nestlings, and an earlier start to the moult may be the primary benefit that he gains.

The rodents' predation intensity and discrimination ability toward the predispersal beechnuts ( Fagus crenata ) were investigated using a tree tower in a beech forest, central Japan in 1999 and 2000. In this stand, using seed traps, the densities of fallen viable nuts were 35.1 m -2 in 1999 and 8.4 m -2 in 2000. The vertebrate-damaged nuts had fallen 5.6 and 2.2 m -2 in 1999 and 2000, respectively. Yet, the crop of viable nuts in 1999 was not so rich as that in a mast year. In 1999, predispersal predation by rodents was recognized at 16-19 m above ground through the bagging experiment. In 2000, there were no predispersal predation and yet we captured Apodemus argenteus three times and Glirulus japonicus frequently on the tree. Judging from the facts of their feeding behaviors and the tooth scars left on the cupules and nuts, Apodemus argenteus might have been more responsible for predation to the predispersal beechnuts rather than Glirulus japonicus . Apodemus argenteus population seemed to be abundant on the ground in both years. If the main agent of predispersal predator were Apodemus argenteus , their number shifted to the canopy would be much larger in 1999 than in 2000 according as the crop of viable nuts. In an additional experiment, rodents preferred intact cupules to insect-damaged cupules on the tree, suggesting that they discriminated the quality of the predispersal nuts, even in the cupule stage, through olfactory and/or visual senses. Thus, predispersal nut predation by rodents was prevalent during the limited period in autumn.