Songbirds are Shrinking
North American songbirds have been shrinking steadily in size over the past 40 years…
The changes were too small to be apparent to the naked eye, the scientists said, amounting to a gram or so in weight per bird and a few millimeters change in individual wing length.
The findings were based on measurements of more than 70,000 birds collected since 1978 at the Field Museum of Natural History in Chicago.
Warm-blooded animals are generally larger in cold climates and smaller in warm climates because more compact creatures usually release heat more quickly, according to biologists and ecologists.
Migrating birds in the modern world face many hazards affecting their growth and survival, from vanishing nesting grounds, dwindling food sources and pesticide use, to domestic cats, which kill up to 3 billion birds annually…
Collisions with high-rise buildings kill another 600 million or so migrating birds every year…