The American MacArthur observed, in 1958, that 5 species of similar warblers coexist on spruce tree because they

Options

A. Eat different kinds of insects
B. Behavioural differences in their foraging activities
C. Cooperate in their foraging efforts
D. Are kept below their carring capacities by predators

Answer

To answer the question regarding the coexistence of five species of similar warblers on a spruce tree as observed by American ecologist Robert MacArthur in 1958, we can break down the solution step by step.

### Step-by-Step Solution:

1. **Understand the Context**:
- In 1958, Robert MacArthur studied the behavior of five species of warblers that lived in the same spruce tree. The question asks why these species can coexist despite their similarities.

2. **Identify the Options**:
- The options provided are:
1. Eat different kinds of insects
2. Behavioral differences in their foraging activity
3. Cooperate in their foraging efforts
4. Are kept below their carrying capacity by predators

3. **Analyze Each Option**:
- **Option 1**: Eating different kinds of insects could allow for coexistence, but this is not the primary reason MacArthur identified.
- **Option 2**: Behavioral differences in their foraging activity is a strong candidate. MacArthur noted that these warblers had different feeding behaviors and foraging times, which allowed them to utilize the same resource without direct competition.
- **Option 3**: Cooperation in foraging is unlikely as these species are generally competitive rather than cooperative.
- **Option 4**: While predators can influence population sizes, they do not explain the coexistence of these warblers directly.

4. **Conclusion**:
- The best explanation for the coexistence of the five species of warblers on the spruce tree is **Option 2: Behavioral differences in their foraging activity**. This means that they forage at different times or in different ways, which reduces competition for the same food resources.

### Final Answer:
The American MacArthur observed that the five species of similar warblers coexist on a spruce tree because they exhibit behavioral differences in their foraging activity.

---