Band and Audience

Saline Valley Farms was an experiment in cooperative farming and living begun in 1932 by Harold S. Gray.

People Washing Farm Products

Saline Valley Farms was an experiment in cooperative farming and living begun in 1932 by Harold S. Gray.

Men beside Cars

Saline Valley Farms was an experiment in cooperative farming and living begun in 1932 by Harold S. Gray.

Construction Field

Saline Valley Farms was an experiment in cooperative farming and living begun in 1932 by Harold S. Gray.

Man by River

Saline Valley Farms was an experiment in cooperative farming and living begun in 1932 by Harold S. Gray.

Man beside Rushing Water

Saline Valley Farms was an experiment in cooperative farming and living begun in 1932 by Harold S. Gray.

Men by Carcass of Pig

Saline Valley Farms was an experiment in cooperative farming and living begun in 1932 by Harold S. Gray.

Man in Hat with Bees

Saline Valley Farms was an experiment in cooperative farming and living begun in 1932 by Harold S. Gray.

Children Playing with Sand

Saline Valley Farms was an experiment in cooperative farming and living begun in 1932 by Harold S. Gray.

Man Looking at Chicken on Lap

Saline Valley Farms was an experiment in cooperative farming and living begun in 1932 by Harold S. Gray.

Man Picking Fruit

Saline Valley Farms was an experiment in cooperative farming and living begun in 1932 by Harold S. Gray.

Report.

Report year irregular.

Des institutions en vue de la transformation ou de l'abolition du salariat /

"12 leçons faites en mai-juin 1919 aux étudiants américains."

Des institutions ouvrières au dix-neuvième siècle /

Publisher listed on cover; printer on t.p.

Division of labour within cooperatively breeding groups

Within cooperative societies, group members share in caring for offspring. Although division of labour among group members has been relatively well studied in insects, less is known about vertebrates. Most studies of avian helping focus solely on the extent to which helpers provision the offspring, however, helpers can participate in everything from nest building to predator defence. Bad provisioners may, for example, not be as 'uncooperative' as they appear. if they are good defenders. Thus, the distribution of helping tasks between group members should have important implications for our interpretation of group dynamics. Here, we compare two distinct forms of helping behaviour in the cooperatively breeding noisy miner (Manorina melanocephala): chick provisioning and mobbing nest predators. We show that the way in which individual helpers invest in these two helping behaviours varies enormously across individuals and among social groups. Good provisioners often contributed relatively little to mobbing and vice versa. Indeed, (18%) of helpers only mobbed, 22% just provisioned, whereas 60% of helpers performed both forms of helping. Across nests, provisioning was significantly negatively correlated with mobbing effort. We suggest that small differences in the costs or benefits of different aspects of helping (due to differences in age, relatedness or social status) have a big impact on the division of labour within a group. Consequently, social groups can be made up from individuals who often specialise in one helping behaviour, and/or helpers who perform a number of behaviours to differing degrees. Division of labour within social groups will, therefore, have important consequences for the maintenance of cooperatively breeding in vertebrates.