Birds are

Options

A. Poikilothermic
B. Ectothermic
C. Cold blooded
D. Endothermic

Answer

To answer the question "Birds are," we will analyze the options provided step by step.

### Step 1: Analyze the first option - Poikilothermic
- **Definition**: Poikilothermic organisms are those whose internal body temperature varies significantly with the temperature of their surroundings.
- **Examples**: This characteristic is typical of reptiles.
- **Conclusion**: Since birds do not have a variable internal temperature like reptiles, this option is incorrect.

### Step 2: Analyze the second option - Ectothermic
- **Definition**: Ectothermic animals, also known as cold-blooded animals, rely on external environmental conditions to regulate their body temperature.
- **Examples**: Common examples include fishes, amphibians, and invertebrates.
- **Conclusion**: Birds do not depend on external temperatures for their body heat regulation, making this option incorrect.

### Step 3: Analyze the third option - Cold-blooded
- **Definition**: Cold-blooded is synonymous with ectothermic and refers to animals whose body temperature is influenced by the environment.
- **Conclusion**: As established in the previous step, birds are not cold-blooded, so this option is also incorrect.

### Step 4: Analyze the fourth option - Endothermic
- **Definition**: Endothermic organisms maintain a constant internal body temperature largely through metabolic processes, independent of external environmental conditions.
- **Examples**: Birds and mammals are primarily classified as endotherms.
- **Conclusion**: Since birds maintain their body temperature through internal heat production, this option is correct.

### Final Answer
Based on the analysis, the correct answer is that birds are **endothermic**.

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