Temperature and other climate variables are currently changing at a dramatic rate. These climatic changes have serious consequences for all birds and their ability to adapt to changing environmental conditions. Birds are excellent example of a sensitive organism, with a very active metabolism; they are highly sensitive to environmental changes. The earth is naturally surrounded by carbon dioxide, methane, and nitrous oxide, so-called greenhouse gases that trap the sun's heat. Since they warm the planet, they make life possible. We need them to survive. But our use of coal, oil, and gas, and other activities, such as the cutting and burning of forests, is adding to the amount of carbon dioxide and other gases in the atmosphere. And the higher the concentration of greenhouse gases becomes, the more heat they trap, and the warmer our planet grows. Indeed, over the last 50 years, the earth's temperature has risen an estimated 1°F (0.6°C). This increase may seem insignificant at first glance, but even small changes in climate may affect birds and their habitats. A change of 1°F is enough to cause sea levels to raise, storms to become more intense, glaciers to retreat, and drought and fire to become more common. Indeed, an ice shelf larger than Manhattan has already broken free from Canada's Ellesmere Island, and ice shelves in the Antarctic are following suit, calving and disintegrating at a significant rate. Birds are affected directly by climate, for example, through their tolerance for a range of temperature or rainfall. They are also affected indirectly, through the effects of climate on their habitat and food supply. Thus as winters become warmer, bird distributions are likely to change, but only as fast as their habitats can respond to the changing climate. So to fully understand or predict how birds will respond to climate change, we need to study not only how they themselves respond to climate, but how the plants and insects and other organisms that make up their habitats will respond. Also the song bird’s egg temperatures: According to Cornell, the optimal range for bird egg development is 96.8 °F to 104.9 °F (36 °C to 40.5 °C). If egg temperatures are lower, embryonic development slows. Higher temperatures can be lethal for the embryo. (Birdscope, Summer 2002, Vol.16 No.3, Cooper and Chu). Bluebird eggs and nestlings cannot survive temperatures exceeding 107 °F (41° C) (Conley Black). Prolonged excessive heat can severely impact nestling health due to dehydration and heat stress. Temperatures inside a nest box can reach 120 °F, and are often at least 10 degrees higher than the outside temperature. Some research indicates that if temperatures outside are 100-104 °F, the percentage of eggs that hatch drop, and nestlings under nine days old can die from heat stress or dehydration. (Up to 6-9 days old, the nestlings are as sensitive as eggs to cold/heat.)
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Wooden nest boxes are found to be cooler according to Cornell, Heat Shields and Screens can be very effective at controlling temperatures inside the nest box. Also a second roof over the primary roof using Styrofoam works like a cooler. We Bluebirders do all we can to help these birds to survive. As temperature and storms increase in severity we need to look at ways to control temperature inside the nest box.
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