SEE-U 2000: Black Rock Forest - Module 13:Exercise 13

## Exercise 13: Risk of Egg Predation and Edge Effects
Module 13: Habitat Fragmentation and Deforestation

### Your Questions

1. How does the fragmentation of formerly intact habitat place pressures on the species using the habitat?
2. More specifically, how does fragmentation and its associated edges influence egg survival?

### Background

Human alteration of large areas of continuous habitat often results in fragments or patches of native habitat surrounded by edges. Species living in the remaining fragmented habitat can be negatively impacted by these edges due to increased contact with humans, elevated temperatures and drying from winds, and competition from or predation by edge-exploiting species. In addition, because the area of the habitat is reduced, population sizes are smaller and therefore more likely to go extinct in any particular patch.

Amongst the best-documented effects of fragmentation is the decline of songbird populations in formerly forested areas. The mechanisms by which this occurs are varied but one of the primary problems appears to be egg or nest predation along edges. This predation occurs when generalist edge-exploiting species increase in numbers as a function of fragmentation and can act to severely limit recruitment of interior species inhabiting the patches.

Today’s activity is based on the idea that if you place many baits at different distances from an edge and monitor the portions of them that are consumed, these portions will constitute an index of the predation pressure from potential bird nest predators.

### Your Assignment

Our goal is to determine if the processes associated with fragmentation such as habitat change, edge effects and borders within formerly continuous habitat influence the probability of predators finding a song bird nest.

This activity will require creating and monitoring artificial nests over several days to monitor predation. To accomplish this, we will conduct this activity concurrently with other activities. Following a lecture on fragmentation and edge effects on songbirds (1 August 2000), the class will divide into several groups. Each group will design their own experimental set-up after consulting the instructors and the current scientific literature. These designs will be presented and discussed on 7 August after which the groups will proceed to their disturbed and control sites and set up their experiments. Examples of edges we can select include those caused by fire, development and construction in the forest, roads adjacent to the forest, parking lot construction, and edges along water. Results and conclusions will be presented on 17 August 2000.

Some of the variables that should be considered are:

1. type of bait
2. location of study
3. number and distribution of bait
4. execution of study
5. placement of controls
6. analysis

Given the unique set-up of this activity, it is not possible to assign time to specific tasks. However, the bulk of your time should be toward designing the experiment, reading the literature handed out, placing the nests in the field and monitoring predation. The actual monitoring (checking for predation) should not require a significant amount of time.

Evaluation will be based on:

1. Design and carrying out of experiment
2. Oral summarization of each groups’ analyses.
3. Participation in discussion of other group presentations. Based on your analyses, do you agree or have additional insights

### Objectives

1. Familiarity with current literature on fragmentation effects on songbird populations.
2. Designing and conducting a field experiment.
3. Determining experimental variables, constraints and limitations.

### Key Skills

1. Increased competence collecting field measurements.
2. Designing, carrying out, and analyzing the results of a field experiment

### Timetable

This activity involves a lecture regarding fragmentation, edge effects on songbird populations, and designing field experiments. This will take place in the afternoon. The students are then given approximately one week to design their experiment. The designs are reviewed in class and the students are then sent out to place the nests in the field.

1. Total elapsed time to perform the experiment: 3 weeks.
2. Total elapsed hands-on time : 18 hours

- Lecture = 1 hr during day 1
- Place artificial nests: 4 hrs during day 7
- Monitor egg survival: 1 hr/day during week 2-3 (10 hr over 10 days)
- Analysis of results: (2 hrs)
- Write-up and discuss results (1 hr).

### Procedural Notes

1. In order to monitor predation through time, this activity requires that the students set up and monitor the nests over several days. Students will be responsible for designing and conducting the field experiment. On the final day of the activity, the students will present their results to the class and discuss their results.
2. This lab, based on Gibbs et al. (1998), is an opportunity for the students to design their own experimental system. How can this be done given the startup time needed (Gibbs suggests the experiment run 2 wks in order to get some results). I propose that on the second day of the turtle population activity (week 2, 1 August), after checking the traps we’ll have an afternoon lecture on fragmentation and edge effects on song bird populations. I will provide some key pieces of literature on the subject and divide the class into 4 groups. Each group will present their design the following week (week 3, 7 August), we’ll make any changes we need to then they will set up their experiments. These will be monitored for 10 days. On 17 August, (week 4) they will present their results to the class.

### Materials Needed

1. Flagging to mark nests
2. Small paper bowls to act as nests
3. Quail eggs or artificial substitute (e.g., plasticine eggs, walnuts)
4. Record sheets

Authors: A. Hoylman, M. Gompper, and heavily based on the Gibbs et al. 1998. Edge Effects: Designing a nest predation experiment.