Counting on Fall by Lizann Flatt, illustrated by Ashley Barron

From chapters.ca:
As young readers journey into the natural world, they will discover that numbers, patterns, shapes - and much more! - can be found by observing everyday plants and animals. What if animals and plants knew math, just like you? Would leaves fall in patterns? Would whales enter a race? In Counting on Fall, the first title in the Math in Nature series by award- winning author Lizann Flatt, nature comes to life to help children grasp concepts of number sense and numeration.

There was an Old Lady who Swallowed Some Leaves! By Lucille Colandro, illustrated by Jared Lee

From chapters.ca:
That wild old lady is back swallowing fall- themed items. What can you make from leaves, clothes, pumpkin and a rope? That's right, a scarecrow! 

Mouse's First Fall by Lauren Thompson, illustrated by Buket Erdogan

From chapters.ca:
One cool day Mouse and Minka venture out to play. From leaves of all colors - red, yellow, orange, and brown - to leaves of all shapes and sizes - from pointy to round - Mouse learns that fall is a season full of fun! And before the day is done he just might take the biggest "leap" of all.

Busy Little Squirrel by Nancy Tafuri

From chapters.ca:
The leaves have started to fall. The air is cold. Squirrel needs to get ready for winter. He cannot nibble with the mice. He does not have time to hop with the frogs or run with the dogs. But there is one thing he can do!

Leaf Man by Lois Ehlert

From chapters.ca:
Fall has come, the wind is gusting, and Leaf Man is on the move. Is he drifting east, over the marsh and ducks and geese? Or is he heading west, above the orchards, prairie meadows, and spotted cows? No one's quite sure, but this much is certain: A Leaf Man's got to go where the wind blows.