In Chapter \(13,\) Figure 13.6 presents a hypothetical case where two bird species overlap in their use of food resources (seeds). Let us assume that due to interspecific competition, the two species cannot co-occur in the same habitat (say species 1 succeeds). Now assume that the distribution of seed sizes in their habitat changes from year to year depending on rainfall, and that the average seed size varies from \(a\) to \(b\) (Figure 13.19 ). How might this temporal variation in resources influence the outcome of competition between the two species?

We are given a hypothetical situation where two bird species, Species 1 and Species 2, cannot co-exist in the same habitat due to interspecific competition for food resources (seeds). We'll assume that Species 1 initially succeeds in this habitat. Over time, the seed sizes in this habitat vary depending on rainfall, ranging in size from `a` to `b`. We are asked to analyze the effects of this seed size variation on the competition between the two bird species.

To determine how this variation in seed sizes might affect competition, we will need to consider the following factors: 1. What is each bird species' preferred seed size range? 2. How does each bird species adapt to changes in seed size? 3. How might these factors ultimately determine the outcome of the competition? Think about the scenario in terms of the birds' abilities to utilize a specific range of seed sizes, and how their feeding preferences and adaptability might change with the varying seed size availability.

The temporal variation in seed sizes may lead to the following possible outcomes: 1. If both bird species have similar preferences and adaptability, they may continue to compete, with one species eventually overtaking the habitat when its preferred seed size is more abundant. 2. If one species is more adaptable to the range of seed sizes, it may eventually be able to exploit the food resource better and succeed in the habitat, regardless of the seed size fluctuation. This may lead to the less adaptable species being outcompeted and pushed out of the habitat. 3. If both bird species have different preferences or adaptability to a range of seed sizes, they may sort themselves into different microhabitats within the larger habitat, each utilizing a distinct range of seed sizes. This separation of resource use reduces competition and might allow both species to coexist.

In conclusion, the temporal variation in seed sizes from `a` to `b` might have important implications for the outcome of the competition between Species 1 and Species 2. The ability of each species to adapt to the changing resources and how well they exploit the available seed sizes will ultimately determine which bird species succeed in the habitat. Before making specific predictions for this hypothetical situation, it would be necessary to understand each species' feeding preferences and adaptability to changing seed sizes. However, the possible outcomes listed above provide starting points for further investigation and discussion.