With the dramatic change in our weather over the past few days, we are finding things are much cooler now and that means that the hummingbirds here (Anna's) need a more concentrated sugar water (nectar). I increase it to 3 to 1 when weather gets colder (1 part sugar 3 parts water). I have just this morning mixed up a fresh batch, making sure the mixture boils and is thoroughly stirred and cooled. I usually keep a bottle of it in the fridge.
Hummingbirds go into a state of torpor when it gets really cold, to conserve their energy. The following article contains some interesting facts about torpor in birds - probably not something to worry about in Wollongong - but Golbourn might be another story ...
How do Hummingbirds survive Cold Nights? Hummingbirds and Torpor
http://scienceblogs.com/grrlscientist/2 ... nd-torpor/
Below is a short extract from the article:
The greatest diversity of hummingbird species is the neotropics (New World tropics) but many species live in or migrate to temperate zones in the United States and Canada to breed. Sometimes, for reasons that are not entirely clear, individual birds remain behind for the winter, and sometimes, they survive. Thus, as average seasonal temperatures increase, hummingbirds are increasingly becoming established as year-round residents outside of their traditional ranges. Anna’s Hummingbird is one species whose range has expanded steadily northward as seasonal temperatures have become milder. Thus, this bird is now a common year-round resident along the northwestern coast of the United States and even into some parts of Canada.
As most people know, hummingbirds feed on flower nectar, which is a tempting “gift” of high-energy sugars provided by flowers in exchange for pollination. In addition to nectar, hummingbirds also consume large quantities of small insects, which are full of higher-energy fats as well as essential proteins. Because of their tremendous metabolic requirements, hummingbirds have voracious appetites. Equivalent to the average human consuming an entire refrigerator full of food, hummingbirds eat roughly twice to thrice their own body weight in flower nectar and tiny insects each day.
Besides being among the smallest of all warm-blooded animals, hummingbirds also lack the insulating downy feathers that are typical for many other bird species. Due to their combined characteristics of small body size and lack of insulation, hummingbirds rapidly lose body heat to their surroundings. Even sleeping hummingbirds have huge metabolic demands that must be met simply to survive the night when they cannot forage. To meet this energetic challenge, hummingbirds save enough energy to survive cold nights by lowering their internal thermostat at night, becoming hypothermic. This reduced physiological state is an evolutionary adaptation that is referred to as torpor.
The full article contains many more interesting facts about this phenomenon.