Black Rock Forest

Exercise 7: Predation Pressure and Avian Behavioral Ecology
Module 7: Consumers: Herbivory, Predation, and Parasitism

Your Questions

1. How do animals behave when faced with various energetic, social, and predator avoidance pressures?
2. More specifically, how is the consumption of food by woodland bird species affected by predation pressure?

Background

Behavior ecology seeks to understand the role that an observed behavior pattern plays in the survival of an animal. An adaptive behavior would be favored by natural selection because it improves the survival and reproductive success of an individual. The response of prey species (e.g. a deer) to predation pressures (e.g. from wolves) might result in defensive or avoidance behaviors that increase survival rate so the individual can live to breed and reproduce another day. In avoiding an encounter with a predator, the prey species would have to balance this behavior against possible loss of acquiring food and the energetic cost to food consumption. That is, if too much energy is expended avoiding a predator at the expense of acquiring food, then the behavior is maladaptive and the prey loses. For example, herbivores in Africa must venture out in to the open to graze regardless of the potential for attack by predators such as lions. To avoid lions completely would mean the herbivore would have to settle for poor quality food out of the view of lions. Alternatively, ignoring predators would also likely result in negative consequences for the prey animal. Thus a balance must be struck by individual animals.

In today’s activity we will be observing the behavior of granivorous (seed-eating) woodland bird species at artificial feeding stations and hypothesizing as to the adaptive function behind the behaviors we observed. It is also possible that squirrels and chipmunks will visit these feeders, in which case the same questions may be asked. One possible selective pressure acting on the behaviors we see in birds is the threat of predation. To further study predation on woodland birds, we will conduct an experiment to assess the affect of distance from cover on foraging behavior.

Your Assignment

Your assignment involves the following tasks:

1. You will observe feeding birds (and possibly mammals such as squirrels) at the experimental bird feeders placed at varying distances from cover, and record differences in behavior between the different species. For each species observed to regularly visit the feeders you will determine the possible effects of predation pressures on behaviors such as: distance animals will travel to obtain food, feeding rates, and vigilence behaviour. (3 hrs)
2. Write-up and discuss results. (2 hrs)

Objectives

1. Understand how animals balance the need to obtain resources with the need to avoid predators.
2. Perform a manipulative experiment to reveal the complexity of animal behaviors
3. Observe the evolved variability in the behavior of different species when faced with similar ecological problems

Key Skills

1. Gain an understanding of behavioral trade-offs.
2. Ability to properly use bionoculars and spotting scopes.
3. Familiarity with common granivorous birds of the eastern deciduous forests.

Timetable

1. Total elapsed time to perform the experiment : One day
   • Set-up, field work, data analysis and and report should all be done in one day
2. Total elapsed hands-on time : approximately Eight hours
   • Training on basic ornithology = 2 hour
   • Field work = 2 hours
   • Analysis of results = 2 hours
   • Writing oral presentation and presenting it = 2 hours

Procedural Notes

1. The TAs would have to initially erect and maintain feeders ahead of time so that the students could just go to the feeders, observe the behaviors, and then return to the lab.
2. Time should be given to the students to become familiar with binocular use and bird identification.

Materials Needed

1. Feeders and seed
2. Watches with second hands
3. Field materials: bird field guides, binoculars, spotting scope(s).