Problem 251 - Objective Biology for NEET

Question

Assertion: All birds, except the ones like koel (cuckoo) build nests for retiring and taking rest during night time (day time for nocturnal). Reason: Koel lays its eggs in the nests of tailor bird.

Step-by-Step Solution

Answer

The reason is correct and it indeed explains the assertion.

Step 1: Understand the Assertion

The assertion is that all birds, except the ones like koel (cuckoo), build nests for retiring and taking rest during nighttime. This is a generally accepted practice among birds.

Step 2: Understand the Reason

The reason given is that a koel (cuckoo) lays its eggs in the nests of a tailor bird. This is a known fact about the koel (cuckoo), a bird known for its brood parasitism behavior.

Step 3: Establish Relationship

Analyze if the reason given can explain the assertion or is connected to it. In this case, because koels (cuckoos) lay their eggs in other birds' nests, it may not be necessary for them to build their own nests.

Step 4: Determine Correctness

Given the connection and specifics of the bird behavior, one can conclude that the reason is a valid explanation for why koels do not follow the general bird behavior of nest building.

Key Concepts

Nest Building

Nest building is a unique and essential behavior among many bird species. Most birds construct nests as they provide a safe environment for laying eggs and raising young chicks. Additionally, nests may serve as a shelter to rest and hide from predators. However, the materials and locations birds choose can vary widely.

• Materials: Birds often use twigs, leaves, grass, feathers, and even human-made materials.
• Locations: Trees, cliffs, building ledges, and even the ground are common nesting sites.

Nest building is not only about physical construction but also illustrates the dedication and instinct of birds to provide a secure start for their offspring. However, not all birds follow this common behavior, as we will explore with brood parasitism.

Brood Parasitism

Brood parasitism is a fascinating survival strategy employed by some bird species. It involves laying eggs in the nests of other birds and relying on these "host" birds to raise their young. The cuckoo, including koels, are well-known for practicing this behavior. They evolved this unique reproductive strategy for several reasons:

• Avoidance of the effort and risk associated with building a nest and caring for the young.
• Maximization of reproductive success by having multiple hosts rear their chicks.
• Reduction of competition for resources by not having a fixed territory.

In these cases, the host birds unknowingly care for the eggs and the resulting chicks as their own. While this behavior might seem unfair, it highlights the intricate adaptability of birds in the natural world.

Nocturnal Birds

Nocturnal birds are adapted to be active during the night rather than the day. This adaptation includes both physical and behavioral traits. Their lifestyles are quite different compared to diurnal birds, which are active during the daytime. Some key characteristics of nocturnal birds are:

• Enhanced night vision with large eyes and specialized retinas to see in low-light conditions.
• Quiet flight, especially in species like owls, to hunt silently.
• Communication using sounds adapted to nighttime acoustics.

While these birds often rest during the day, finding refuge in trees or hidden nests, their unique adaptations emphasize the diversity within avian species. Understanding nocturnal birds helps us appreciate the varied lifestyles and survival strategies of birds globally.