When asked “name a bird you see often”, most city-dwellers would name a pigeon or a sparrow. These two birds are the most famous urban birds that are closely associated to humans. The sparrow, being very opportunistic and adaptable, have easily taken over environments around the globe, especially those where European settlements were made. Nowadays, they are regarded as a pest due to their foraging of agricultural crop and the spread of disease. However, citizens still view them in a positive light, especially in parks or gardens where the sparrows appear to be a “symbol of nature” (ironically, they are likely an invading species driving away native birds).
One interesting fact regarding sparrows that most people do not seem to know is how to differentiate a male and female sparrow.
A female sparrow has very soft, brown feathers, with no marked features.
A male sparrow has areas of dark brown or black feathers, especially on the head and eyes. Its beak is also darker than the female.
If one observes carefully at sparrows, they can notice that the two behave slightly differently as well.
The most famous characteristics of a bat is its behaviour of hanging upside down. This strange behaviour actually greatly benefits a bat’s survival. Because a bat’s wing is structurally different to a bird’s, it cannot generate enough flight to lift a bat off the ground directly. Therefore, bats leap off a high location to fly, so hanging from a high place allows them to fly off at any given moment. Also, living in a high place provides protection from predators.
A bat’s anatomy has heavily adapted to accommodate this behaviour. Thanks to its unique anatomical structure, a bat expends no energy while hanging. This is because they have talons that are designed to clench naturally when pulled by gravity, as the tendons tense. Thus, when hanging upside down, a bat can rest peacefully, and can even sleep in that posture as it requires no muscle action (all muscles relax in REM sleep).
As it is the norm to live upside down, a bat does everything in that manner. As stated above, a bat sleeps upside down, eats upside down, mate upside down, and even stay like that after death. There is only one time a bat stands upright: when it excretes waste. Even behaviour cannot overcome the power of gravity.