Herring gulls show Type III survivorship for young followed by type II survivorship for adults. Population is also limited by density independent factors such as storms, weather, drought, floods, and volcanoes. A declining death rate exceeds the decline in births, producing a net increase in people. Industrial stage shows first decline in birth rate. Expanding populations have more young people and few old people.
Stable populations have fewer young people but many reproductive people.
Declining populations have few young and reproductive age people, and many old people. The US has a slow growth, nearly stable population. Germany and other European countries have declining populations. These people will provide large population increases as they become reproductive. US is experiencing net population growth due to baby boomers now having children.