Discover the characteristics common to the 9000 bird species living on Earth today.
- Birds are vertebrates and have lightweight bones.
- Birds are warm-blooded.
- All birds, including flightless birds, have wings.
- All birds reproduce by laying eggs.
There are close to 9000 different species of bird living on Earth today.
Although birds vary dramatically in appearance, all species share a number of characteristics.
Birds all have feathers, one of the defining features of these warm-blooded vertebrates.
The light-reflecting pigments on their feathers help them maintain a constant internal ...
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