Bill Size Matters

Now that we have covered prey adaptations, let us discuss predator adaptations. If prey adapt to avoid being captured, then the predator must adapt as well in order to gain energy through food. As discussed in the previous blog, adaptations must be heritable and increase the organism’s fitness. In the following experiment, we will be discussing the adaptation of beak lengths of birds.

In a fictional land called “Clipland,” there are three different beak lengths demonstrated by binder clips, a large, medium, and small. Beaks are randomly assigned to students and each student is given a cup as a stomach. The group will be split in two to represent “West Clipland” and “East Clipland.” Prearranged food bags will be given out to the two sides in rounds as shown in the table below:

	2nd Season	3rd  Season	4th Season
East Clipland	4 handfuls popcorn seeds ½ lb lima beans 50 marbles	1 handful popcorn 20 lima beans 50 marbles	100 marbles
West Clipland	4 handfuls popcorn ½ lb lima beans 50 marbles	6 handfuls popcorn 20 lima beans 5 marbles	8 handful popcorn

Each group starts at season two at separate areas. They are given 15 seconds to pick up as many items as they can only with the binder clips and place them in their stomach. Each item is given a different point worth and each beak size is assigned a goal of points in order to survive. Double the assigned points to survive for a reproduction point goal. At the end of the round, all those who reached their survival goal will move on to the next round and any who failed to reach the goal will become a spectator. If any of the survivors obtained enough point to reproduce, a spectator may rejoin as its offspring with the same beak length as its parent. After the survivors and offspring have been tallied, they will empty their stomachs in the original bag to clean up the “feeding” space and spread out season two’s feed bag. Repeat this process for season three and four. After season four, clean up all the materials and tally the results of “East Clipland” and “West Clipland.” The first season is the original population of each beak length before the beginning of season two. My personal demonstration resulted as follows:

West Clipland

	1st Season	2nd Season	3rd Season	4th Season
Bigbill	2	0	0	0
Mediumbill	3	3	1	1
Smallbill	2	2	1	0

East Clipland

	1st Season	2nd Season	3rd Season	4th Season
Bigbill	4	2	2	3
Mediumbill	3	0	0	0
Smallbill	3	2	2	0

As shown in the table above, the fitness of the organisms fluctuates with the size of food available. When marbles were most prominent, bigbill binder clips were favored. When popcorn was the prominent food source, the smallbill binder clips were favored. These results show the short term natural selection. Intraspecies competition is apparent as the different sized beaks as some beak lengths were ultimately eliminated. For this purpose, Clipland is an excellent example of predator adaptations in contrast to prey adaptation.

Credit to Al Janulaw and Judy Scotchmoor