A researcher is interested in the field metabolic rate of mocking birds (Mimus p

Question

A researcher is interested in the field metabolic rate of mocking birds (Mimus poolyglottus). She captures birds and brings them into the laboratory for measurments of VO2. She determines that the resting metabolic rate of caged mockingbirds is 127 kilojoules (kj) per day. Based on previous studies of avian energetics, she knows that various activities elevate metabolic rate above the resting level by the following magnitudes:

Foraging = 3.4X. Flying = 2.2X. Singing = 1.4X

The investigator then goes into the field to construct time budgets for wild mockingbirds. She obtains the following results for the birds' daily activities (Mean % of time spent on each activity per day):

Foraging = 32%. Flying = 6%. Singing = 40%. Misc. (Sleeping or Resting) = 22%

A. Calculate the daily energy cost for each of the mockingbirds activities. Hint: You must assign a value for the metabolic cost of the "miscellaneous" activities.

B. Calculate the mockingbird's total daily energy expenditure in the wild.  

C. What conclusions or generalizations can you draw from these values?

Explanation / Answer

A)
1) The birds when in lab metabolise at 127 Kj/day - now, for one percent of a day, the birds metabolise at 127/100 = 1.27 Kj/percent of day.
?Now, Foraging accelarates metabolism by 3.4 times. So, metabolic rate becomes 3.4 x 1.27 Kj/percent of day. Total energy for foraging = energy per percent of day x time spent doing the task = 3.4 x 1.27 x 32 = 138 Kj.

2) The birds when in lab metabolise at 127 Kj/day - now, for one percent of a day, the birds metabolise at 127/100 = 1.27 Kj/percent of day.
?Now, flying accelarates metabolism by 2.2 times. So, metabolic rate becomes 2.2 x 1.27 Kj/percent of day. Total energy for flying = energy per percent of day x time spent doing the task = 2.2 x 1.27 x 6 = 17 Kj.

3) The birds when in lab metabolise at 127 Kj/day - now, for one percent of a day, the birds metabolise at 127/100 = 1.27 Kj/percent of day.
?Now, Singing accelarates metabolism by 1.4 times. So, metabolic rate becomes 1.4 x 1.27 Kj/percent of day. Total energy for singing = energy per percent of day x time spent doing the task = 1.4 x 1.27 x 40 = 71 Kj.

4) Misc. tasks including sleeping and resting which must be performed by birds usually when they are in lab as well. Therefore, value of metabolism for misc. tasks must be considered equal to laboratrical metabolism value.
?So, 1.27x1x22 = 28 Kj/day.

B) Total energy expenditure per day must be the summation of individual expenditures.
Foraging + Flying + Singing + other = 138+17+71+28 = 254 Kj/day.

C)

C)
1) The energy calculations come in play when we want to understand what birds do when they live where they must. It explains the rise in energy requirement when birds live in natural environment.

2) Energy cost for foraging is maximum. It is of particular interest to fisherman and fishery biologists. It also intrests ecologists.

3) Though these are only estimates and these vary daily and seasonally, we see here that a bird in wild uses almost double the energy it does in lab.

4) Also, birds are warm blooded organisms, and in lab the need to maintain body temperature decreases drastically. In the wild, this accounts for a major reason of energy expenditure.

5) Energy for singing is second highest. This is observed that birds that practice singing (Passerines) have more metabolic energy requirement than birds who don't (Nonpasserines)

6) Also, food habits of birds and the altitude where they live also influence the metabolic rate of birds.

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