How does the ideal free distribution work?

Question

I have recently completed a study on Brent Goose. I found that Brent Geese occupy high quality habitat first then once this is full of geese, they fill up low quality habitat. However, there were always fewer geese in the low quality habitat. This pattern therefore seems like a good match for the ideal free distribution…but is it? Under the ideal free distribution, do birds fill up high quality first, then low quality habitat second? Or do birds fill up both high and low quality habitats simultaneously, but fill up high quality at a faster rate? Or does the ideal free distribution not make explicit the order/rate at which birds fill up high and low quality habitats?

Answer 1

Hi! So according to ideal free distribution, if there are two patches, say High Ground and Low Ground, and Low Ground is twice as rich in food sources as High Ground, then Geese will occupy the Low Ground at twice the rate as the High Ground. This means that there will still be geese in both habitats, twice as many in Low Ground. So your second conjecture was correct: "...birds fill up both high and low quality habitats simultaneously, but fill up high quality at a faster rate".

Remember that IFD has a lot of assumptions, so if you don't see it clearly in your population of geese, there could be something that violates one of the assumptions (physical barriers preventing free movement, unequal competitors, etc).