Naturespeak 

Hummingbirds and the anti-Atkins Diet

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Studies have indicated that the reason hummingbirds spend 10-15 minutes of every hour foraging is that they need the rest of the time for digestion. The average transit time of nectar through a hummingbird’s digestive system is one hour, during which 97 per cent of the sugars are extracted, to be used for energy requirements.

In comparison the human digestive system extracts 50 per cent of the sugars from most carbohydrates. For the other 45-50 minutes the hummingbird is emptying its crop. A "crop" is a specially modified part of the digestive system that stores food immediately after it is taken in. We do not have these.

The hummingbird must wait until its crop is half empty, which takes about 4 minutes, before foraging again. Thus, they forage only as often as required to maintain the rate at which the crop passes nectar into the rest of the digestive system. In the meantime, the hummingbird conserves energy by remaining immobile, as flying require eight times as much energy.

Besides its high carb diet the hummingbird does need some protein and fat and gets these by feeding on pollen and the small insects that it finds in flight or on flowers.

In addition to spending the majority of their daylight hours sedentary, hummingbirds become torpid at night to conserve energy. "Torpid" means they let their body temperature; the temperature is regulated at a level similar to the surrounding air of their local environment. Their normal body temperature is approximately 40°C but it can drop to 20°C. The decrease in body temperature results in a reduction in their metabolism. Thus, at its normal body temperature a hummingbird could lose 10 per cent of its body weight per night, while a torpid state this results in only a 1 per cent loss.

Hummingbirds, tiny marvels that they are, are a prime example of how a high carb, sedentary and even at times torpid lifestyle can be essential for survival in some animals.

Thanks for all those who contacted me with their early season hummingbird sightings, though no one was able to beat Bobbi Sandkul of Pinecrest Estates and her sighting of March 27th. Once again, for help identifying our local hummingbirds go to: http://www.mangoverde.com/birdsound/fam/fam86.html .

Upcoming Events:

Monthly Bird Walk — The next bird walk will take place Saturday, May 1st. Join Whistler experts in the monthly update of our feathered locals and migrants. For details, contact Michael Thompson: 604-932-5010.

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