The Elements of Habitat

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Space is often left out of habitat definitions, because it isn't as easy to define as food, water and shelter. Space is a very important element of habitat and the amount of space needed varies among wildlife species.

The bald eagle is a good example of a species that needs a lot of space. A bald eagle has very specific habitat requirements. They prefer clean water, with an abundant amount of fish, need trees, up to 100 ft tall, for perching and nesting and plenty of space in which to fly. A bald eagle may fly up to 200 miles in a single day!

In addition to space in which to fly, the bald eagle needs space, un-invaded by humans. This is the type of space that becomes difficult to define; the amount of space an animal needs before it runs/flies/crawls away.

For bald eagles, this may be 100 yards. Meaning, if you get within 100 yards of a

Bald Eagle
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perching bald eagle, the eagle will fly away.

Sandhill cranes will sleep the night away in open water, where predators cannot easily sneak up on them. Whooping cranes, an endangered species, require almost twice as much water around them before they will rest for the night.

As you spend more time around wildlife, you will notice a difference in space requirements. Along the nature trails, you will notice that herons and ibis will fly off before you get within 100 ft, but geese will allow you to walk right by the marsh without flying away. If you got off of the trail and moved closer, they might fly, but they are comfortable with the distance from the trail to the water. Being quiet and moving slow will improve your chances of seeing wildlife before you scare them off.

Another space need is space for migration. Wildlife migrate south, to warmth and food, when it gets cold in the north. And then, they fly back north, in the spring.

Let's look at the Killdeer migration, to the left. This 10.5 in. bird spends summers in the U.S. It then migrates to the S. United States, Mexico or Central America in

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winter and flies, each spring, to the Artic Circle to breed. This round-trip journey exceeds 20,000 miles!

This is how much space that the killdeer needs in a year, but the "home range" space needs are different. A killdeer's daily life, for example: in the summer, may require the "home range" of a football field. And we already know that a bald eagle can require up to 200 miles a day! So, space is species-specific and can't be generalized for all wildlife.

The space needed for daily activity and the space needed for migration are both space elements that wildlife depend upon in a healthy habitat. With the use of fences, highways and buildings, humans created barriers in habitat. With our highways and fences, we made it difficult for wildlife to move across the land.

While we may think of migrants as being birds - and birds being able to fly over barriers, migrants are not always birds. And even when it is a bird, flight may not be a solution, as in the picture to the left. This mother mallard is likely in molt and cannot fly (adult ducks annually lose their flight feathers and re-grow them; when they have not yet regrown the feathers, they are "in molt"). Regardless, her ducklings can not yet fly and the highway has become a difficult barrier.

Space isn't the only important factor. Sometimes the problem is food, water or shelter. A farm field has a lot of space, but unless it is farmed in something that wildlife will eat, it can't be used as habitat. And if it is something, like cowpeas, that wildlife will eat, there needs to be water at a short distance and cover (such as bushes, trees or tall grass) to complete all 4 elements of habitat.

The biggest problem for wildlife came when the land became obstructed with housing developments and buildings, wetlands were drained or filled and habitat was converted to farmland - making available habitats and home ranges so small that some animals populations began to decrease because they simply didn't have enough habitat.