Correct option is D
Ans. 4. The syrinx muscles are unable to move freely after early morning, resulting in poorer control over song production at later times of the day.
Sol. Let's analyze each option:
Option 1: Transmission of sound is better at dawn due to colder temperature at that time
True: Sound transmission tends to be better during the early morning hours when the air is cooler and denser. Colder air increases sound propagation, especially for lower frequencies, which are typically used in bird songs.
Option 2: Singing at dawn is costly as the birds are low on energy. This makes singing at dawn a handicap and thereby indicates honest signalling
True: Singing at dawn can be energetically costly, and if a bird is still able to sing well, it indicates that it is in good condition and able to perform despite low energy. This is considered a form of honest signaling, where only healthy birds can afford to sing at this time.
Option 3: Dawn chorus allows birds to utilise a time window for singing which does not interfere with their feeding time
True: The early morning hours, when birds are still resting or waiting for food, provide a time window for birds to engage in singing without interfering with their foraging activities. This makes dawn a good time to sing as it doesn’t impact their feeding schedule.
Option 4: The syrinx muscles are unable to move freely after early morning, resulting in poorer control over song production at later times of the day
False: There is no evidence to support that the syrinx muscles (which control bird song) lose their ability to produce songs as the day progresses. Birds typically have full control over their syrinx muscles throughout the day. The Dawn Chorus is more about timing and ecological factors (like sound transmission) rather than any limitation in song production later in the day.
Information Booster
Dawn Chorus: Birds singing at dawn often do so because of favorable environmental conditions, such as better sound transmission due to cooler temperatures and a lack of background noise. It is also energetically costly and serves as a signaling mechanism to indicate the bird's health and fitness to others in the area.
Syrinx muscles: The syrinx is a unique vocal organ in birds that allows for complex and varied sounds. There is no evidence supporting that syrinx muscles become less efficient as the day progresses. Instead, the timing of dawn chorus is more closely tied to behavioral and environmental factors rather than physiological constraints in muscle function.
Additional Information
Option 1 and Option 2 are both accurate explanations for the phenomenon of Dawn Chorus.
Option 3 offers a valid behavioral explanation that singing at dawn doesn't interfere with feeding, which aligns with the natural behaviors of many bird species.
Option 4 is the incorrect explanation because there is no physiological limitation on syrinx function later in the day that would restrict song production.
