Q: Why would you want a chicken-proof umbrella?
A: To use when the weather is fowl!

Explanation: Spring started back on March 19 in the northern hemisphere, while fall began for me here in the southern hemisphere.  As the seasons change, I hope all of you are safe and healthy amid the coronavirus pandemic.

The word ‘proof‘ has many meanings.  In this joke, chicken-proof means that the chickens cannot get in.  This is just like the word waterproof or bulletproof where the water or the bullet cannot enter.   Umbrellas, of course, are waterproof so that the water can not go through the umbrella and get you wet.  (Normally we do not think about umbrellas as being chicken-proof.)

‘Fowl‘ means a type of bird that includes chickens, turkeys and ducks. ‘Foul,’ which sounds the same as ‘fowl,’ means something that is really unpleasant, like really bad weather.

This joke is funny because it plays with the words foul (really unpleasant) and fowl (birds like chickens, turkeys and ducks).  And you would never expect chickens to fall during bad weather, foul weather!

If you want to raise your own chickens (and you have more space than I do) you could watch this