Name:______Section:______

Population Size Scenarios

Owls

Underline any interesting facts that you read in the paragraph below!

An owl is a bird that is solitary (they are usually found alone) and nocturnal (awake at night). Owls mostly hunt small mammals, insects, and other birds. Owls have large forward-facing eyes and ears, a sharp beak, and usually a circle of feathers around each eye. Owls have two large eyes that are fixed in place, so they must turn their entire head in order to change their views.

Owls are far-sighted, and are unable to clearly see anything within a few inches from their eyes. Their ability to see far away objects, particularly in low light, is incredibly good. And owls can turn their head 180 degrees around! Many owls can also hunt by sound in total darkness. Different species of owls make different sounds.

1.  Fill in the missing information in the chart below. Remember, that births and immigration would INCREASE the population size. Deaths and Emigration would DECREASE the population size.

Time
(X) / Original Population Size / Number of Births / Number of Deaths / Immigration / Emigration / End of Season Population (Y)
Season 1 / 3000 / 550 / 800 / 200 / 50 / Ex/ 3000 + 550 – 800 + 200 – 50 = 2900
Season 2 / 2900 / 650 / 700 / 150 / 100 / ______
Season 3 / ______/ 500 / 450 / 300 / 400 / ______
Season 4 / ______/ 570 / 500 / 100 / 50 / ______
Season 5 / ______/ 800 / 900 / 350 / 100 / ______
Season 6 / ______/ 600 / 150 / 300 / 780 / ______

2.  On the back of this page, create a graph of time versus population. Graph paper and Instructions for the graph are on the back of this page.

3.  Was the population of owls stable over time? If something is stable, it means that it generally stays the same over time. If something is unstable, it means that there are significant (large) changes over time.

Circle One: STABLE UNSTABLE

a) If the population was stable, how do you know that it was stable?

b)  If the population was unstable, what do you think caused that change (ex/ a disease? A drought? Death? Birth? Immigration?)